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We collected developmental, survival, and reproduction data for Aphis fabae Scopoli (Hemiptera: Aphididae) reared on faba bean, Vicia faba L. ‘Sevilla’ at four constant temperatures (15, 20, 25, and 30°C), 70% relative humidity, and a photoperiod of 16:8 (L:D) h. The highest intrinsic rate of increase (r = 0.4347 d-1) and finite rate (λ = 1.5445 d-1) were observed at 25°C. The population projection based on the age-stage, two-sex life table quantitatively revealed the growth potential and stage structure of the aphid. We have included the following suggestions to aid researchers in life table studies: 1) The bootstrap method should be used to estimate the variance and SEs of developmental time, survival rate, fecundity, and population parameters. 2) The required number of bootstraps is dependent on the life table data—the higher the variation among individuals, the higher the number of bootstraps should be. In most cases, we suggest that 100,000 bootstraps should be used to obtain a stable estimate of variance and SEs. 3) Computer projection based on the age-stage, two-sex life table should be used to reveal the stage structure during population growth. 4) We used a simple equation based on the total fecundity, survival rate to adult stage, and first reproductive age to detect possible errors in life table parameters. 5) To assist readers in comprehending results, life table studies should include the cohort size, preadult survival rate, number of emerged female adults, mean fecundity, survival and fecundity curves, and population parameters.
Turmeric is an important spice crop with documented human health benefits associated with chemicals called curcuminoids. In this study, the termite Reticulitermes flavipes (Kollar) was exposed to different solvent extracts of turmeric to investigate potential termiticidal properties. Treating termites with hexane extracts of purified lab-grade curcuminoids had no effect on termites. However, in continuous exposure assays, the LC50 for hexane extracts of crude turmeric powder was 9.6 mg, or 1.0mg starting material per square centimeter of filter paper substrate. These active components were soluble in a range of polar and apolar solvents, but only hexane could selectively fractionate active components away from the inactive curcuminoids. The active constituents of turmeric separated by thin layer chromatography (TLC) fluoresced in short-wave UV light but were not visible in long-wave UV light. By reextracting TLC-separated bands in hexane and performing bioassays and gas chromatography—mass spectrometry, we demonstrated that termiticidal components of turmeric are extractable as a blend containing mainly ar-turmerone, turmerone, and curlone. This determination is consistent with findings of preceding work by other researchers that investigated insecticidal properties of turmeric in other pest insects.
Honey bees are at an unavoidable risk of exposure to neonicotinoid pesticides, which are used worldwide. Compared with the well-studied roles of these pesticides in nontarget site (including midgut, ovary, or salivary glands), little has been reported in the target sites, the brain. In the current study, laboratory-reared adult worker honey bees (Apis mellifera L.) were treated with sublethal doses of imidacloprid. Neuronal apoptosis was detected using the TUNEL technique for DNA labeling. We observed significantly increased apoptotic markers in dose- and time-dependent manners in brains of bees exposed to imidacloprid. Neuronal activated caspase-3 and mRNA levels of caspase-1, as detected by immunofluorescence and real-time quantitative PCR, respectively, were significantly increased, suggesting that sublethal doses of imidacloprid may induce the caspase-dependent apoptotic pathway. Additionally, the overlap of apoptosis and autophagy in neurons was confirmed by transmission electron microscopy. It further suggests that a relationship exists between neurotoxicity and behavioral changes induced by sublethal doses of imidacloprid, and that there is a need to determine reasonable limits for imidacloprid application in the field to protect pollinators.
The objective of this study was to assess the effectiveness of a cooperative breeding program designed to enhance winter survival of honey bees (Apis mellifera L.) when exposed to high levels of varroa (Varroa destructor Anderson and Trueman) in outdoor-wintered and indoor-wintered colonies. Half of the colonies from selected and unselected stocks were randomly assigned to be treated with late autumn oxalic acid treatment or to be left untreated. Colonies were then randomly assigned to be wintered either indoors (n = 37) or outdoors (n = 40). Late autumn treatment with oxalic acid did not improve wintering performance. However, genotype of bees affected colony survival and the proportion of commercially viable colonies in spring, as indicated by greater rates of colony survival and commercially viable colonies for selected stock (43% survived and 33% were viable) in comparison to unselected stock (19% survived and 9% were viable) across all treatment groups. Indoor wintering improved spring bee population score, proportion of colonies surviving, and proportion of commercially viable colonies relative to outdoor wintering (73% of selected stock and 41% of unselected stock survived during indoor wintering). Selected stock showed better “tolerance” to varroa as the selected stock also maintained higher bee populations relative to unselected stock. However, there was no evidence of “resistance” in selected colonies (reduced mite densities). Collectively, this experiment showed that breeding can improve tolerance to varroa and this can help minimize colony loss through winter and improve colony wintering performance. Overall, colony wintering success of both genotypes of bees was better when colonies were wintered indoors than when colonies were wintered outdoors.
Bois noir is an economically important grapevine yellows that is induced by ‘Candidatus Phytoplasma solani’ and principally vectored by the planthopper Hyalesthes obsoletus Signoret (Hemiptera: Cixiidae). This study explores the ‘Ca. P. solani’ genetic variability associated to the nettle—H. obsoletus and bindweed—H. obsoletus systems in vineyard agroecosystems of the central-eastern Italy. Molecular characterization of ‘Ca. P. solani’ isolates was carried out using polymerase chain reaction/ restriction fragment length polymorphism to investigate the nonribosomal vmp1 gene. Seven phytoplasma vmp-types were detected among the host plants- and insect-associated field-collected samples. The vmp1 gene showed the highest polymorphism in the bindweed—H. obsoletus system, according to restriction fragment length polymorphism analysis, which is in agreement with nucleotide sequence analysis. Five vmp-types were associated with H. obsoletus from bindweed, of which one was solely restricted to planthoppers, with one genotype also in planthoppers from nettle. Type V12 was the most prevalent in both planthoppers and bindweed. H. obsoletus from nettle harbored three vmp-types, of which V3 was predominant. V3 was the only type detected for nettle. Our data demonstrate that planthoppers might have acquired some ‘Ca. P. solani’ profiles from other plant hosts before landing on nettle or bindweed. Overall, the different vmp1 gene rearrangements observed in these two plant hosts-H. obsoletus systems might represent different adaptations of the pathogen to the two host plants. Molecular information about the complex of vmp-types provides useful data for better understanding of Bois noir epidemiology in vineyard agroecosystem.
Studies done in Brazilian soybean, Glycine max (L.) Merril, in the 1970s suggested the redbanded stink bug, Piezodorus guildinii (Westwood), is principally responsible for delayed maturity in this crop. This stink bug species has recently emerged as a serious pest of soybean in the southern United States, where little is known about its association with the occurrence of delayed maturity disorder. Also, the mechanism behind stink bug-induced soybean delayed maturity remains unknown. It is believed that stink bug feeding during pod development stages results in reduced pod-seed load, causing alteration of source—sink ratio and eventually delayed maturity. To determine the P. guildinii threshold triggering delayed maturity in soybean, experiments were conducted with varying levels of P. guildinii infestation (0, 2, 4, and 8 adults per 0.3 m) during the R4 to R5 soybean growth stages. In addition, to determine if soybean delayed maturity is exclusively because of reduced pod load, experiments with different levels of mechanical pod removal (0, 25, 50, and 75%) were conducted on field-grown soybeans. P. guildinii densities up to 4 adults per 0.3 m did not trigger occurrence of delayed maturity. However, a density of 8 adults per 0.3 m produced a significant increase in the number of green leaves retained on plants at maturity (i.e., delayed maturity). There was no effect of mechanical pod removal on green leaf retention. The lack of a significant positive correlation between mechanical pod removal and green leaf retention indicates the involvement of mechanism(s) other than reduced pod load in the occurrence of soybean delayed maturity.
Maize (Zea mays L.) and wheat (Triticum aestivum L.) are the most important cereal crops for the Argentinean economy and are affected by several diseases. Different planthopper species transmit causal agents of some of those diseases, including Mal de Río Cuarto virus, barley yellow striate mosaic virus, and the recently proposed maize yellow striate virus. Many planthopper species are sap feeders and therefore are expected to host bacteria providing essential nutrients lacking in the diet. Previous studies have evidenced that some of these bacterial symbionts are involved in the virus transmission. Wolbachia is a group of obligate intracellular bacteria infecting numerous arthropod species and causing reproductive alterations in their hosts. These bacteria have been detected in planthopper species, considered rice pests in various regions of the world. To date, Wolbachia infection status of planthopper species of Argentina is unknown. Amplification by PCR and sequencing of 16S rDNA, wsp- and ftsZ-specific genes demonstrated Wolbachia infection in Caenodelphax teapae (Fowler), Delphacodes kuscheli Fennah, Pyrophagus tigrinus Remes Lenicov & Varela, Tagosodes orizicolus (Muir), and Toya propinqua (Fieber). This is the first report of Wolbachia in delphacid vectors of viruses affecting maize and wheat. An understanding of the bacterial diversity harbored by these insect vectors could lead to new options for future management of diseases of economically important crops in a developing country.
Coinfections are common, leading to pathogen interactions during transmission and establishment in a host. However, few studies have tested the relative strengths of pathogen interactions in vectors and hosts that determine the outcome of infection. We tested interactions between two genetically distinct variants of the mealybug-transmitted Grapevine leafroll-associated virus 3. The transmission efficiency of each variant in single variant inoculations by two vector species was determined. The effects of vector species, a coinfected source, and simultaneous inoculation from multiple hosts to one host on variant establishment were examined. Within-vector interactions could have a role in transmission from hosts containing mixed infections, but not when vectors were moved from separate singly infected source plants to a single recipient plant. The invasive Planococcus ficus (Signoret) was a more efficient vector than Pseudococcus viburni (Signoret). Transmission efficiency of the two variants did not differ in single variant inoculations. Overall infections were the same whether from singly or coinfected source plants. In mixed inoculations, establishment of one variant was reduced. Mixed inoculations from two singly infected source plants resulted in fewer mixed infections than expected by chance. Therefore, the observed outcome was determined subsequent to host inoculation rather than in the vector. The outcome may be due to resource competition between pathogens. Alternatively apparent competition may be responsible; the pathogens' differential ability to overcome host defenses and colonize the host may determine the final outcome of new infections. Detailed knowledge of interactions between pathogens during transmission and establishment could improve understanding and management of disease spread.
Enrique G. Medrano, Alois A. Bell, Jeremy K. Greene, Phillip M. Roberts, Jack S. Bacheler, James J. Marois, David L. Wright, Jesus F. Esquivel, Robert L. Nichols, Sara Duke
In 1999, crop consultants scouting for stink bugs (Hemiptera spp.) in South Carolina discovered a formerly unobserved seed rot of cotton that caused yield losses ranging from 10 to 15% in certain fields. The disease has subsequently been reported in fields throughout the southeastern Cotton Belt. Externally, diseased bolls appeared undamaged; internally, green fruit contain pink to dark brown, damp, deformed lint, and necrotic seeds. In greenhouse experiments, we demonstrated transmission of the opportunistic bacterium Pantoea agglomerans by the southern green stink bug, Nezara viridula (L.). Here, green bolls were sampled from stink bug management plots (insecticide protected or nontreated) from four South Atlantic coast states (North Carolina, South Carolina, Georgia, and Florida) to determine disease incidence in the field and its association with piercing—sucking insects feeding. A logistic regression analysis of the boll damage data revealed that disease was 24 times more likely to occur (P = 0.004) in bolls collected from plots in Florida, where evidence of pest pressure was highest, than in bolls harvested in NC with the lowest detected insect pressure. Fruit from plots treated with insecticide, a treatment which reduced transmission agent numbers, were 4 times less likely to be diseased than bolls from unprotected sites (P = 0.002). Overall, punctured bolls were 125 times more likely to also have disease symptoms than nonpunctured bolls, irrespective of whether or not plots were protected with insecticides (P = 0.0001). Much of the damage to cotton bolls that is commonly attributed to stink bug feeding is likely the resulting effect of vectored pathogens.
The wheat curl mite, Aceria tosichella Keifer, is an eriophyid pest of wheat, although its primary economic impact on wheat is due to the transmission of Wheat streak mosaic (WSMV), Wheat mosaic (also known as High Plains virus), and Triticum mosaic (TriMV) viruses. These viruses cause significant annual losses in winter wheat production throughout the western Great Plains. Temperature and humidity are factors that often influence arthropod survival, especially during dispersal from their hosts, yet the impact of these two factors on off-host survival has not been documented for wheat curl mite. Pathogen-infected host plants often influence the biology and behavior of vectors, yet it is not known if virus-infected wheat affects off-host survival of wheat curl mite. The objectives of this study were to 1) determine if temperature, relative humidity, and mite genotype impact off-host survival of wheat curl mite and 2) determine the effect of WSMV- and TriMV-infected host plants on off-host survival of wheat curl mite. Temperature and relative humidity significantly affected off-host survival of wheat curl mite. Length of survival decreased with increasing temperature (106.2 h at 10°Cand 17.0 h at 30°C) and decreasing relative humidity (78.1 h at 95 and 21.3 h at 2%). Mites from TriMV-infected host plants had ∼20% reduction in survival at 20°Ccompared with those from WSMV-infected plants. The duration of off-host survival of wheat curl mite is influenced by environmental conditions. Management strategies that target a break in host presence will greatly reduce mite densities and virus spread and need to account for these limits.
The tomato moth, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a key pest of tomato, Lycopersicon esculentum L., crops in Central and South America. At present it is dispersing rapidly in Africa and Eurasian continents as an invasive pest, threatening worldwide tomato production. Pseudapanteles dignus (Muesebeck) (Hymenoptera: Braconidae) is an American endoparasitoid reported as the main natural enemy of T. absoluta in commercial tomato. To gain knowledge of the potential role of P. dignus in the biological control of this pest, we determined its population parameters in laboratory and the parasitoid's impact on T. absoluta in the field. In laboratory, lifetime fecundity was 193 eggs per female, and longevity was 24 and 26 d for female and male, respectively. The finite rate of increase (λ) was 1.15 per female per day and the intrinsic rate of natural increase (rm) was 0.14. The net reproductive rate (R0) was found to be 51.2, and generation time (T) 28.8 d. The time for doubling the population (DT) was 5 d. Furthermore, field parasitism of T. absoluta varied between 33 and 64% in the different years studied. Population parameters estimated in this study can be considered baseline information for a mass-rearing protocol of this parasitoid. Moreover, growth rates of P. dignus, particularly rm, and its impact on field populations of T. absoluta indicated that this parasitoid is a valuable candidate for biological control of this pest.
Solenopsis invicta Buren is an important invasive pest that has a negative impact on biodiversity. However, current knowledge regarding the ecological effects of its interaction with honeydewproducing hemipteran insects is inadequate. To partially address this problem, we assessed whether the interaction between the two invasive species S. invicta and Phenacoccus solenopsis Tinsley mediated predation of P. solenopsis by Propylaea japonica Thunbery lady beetles using field investigations and indoor experiments. S. invicta tending significantly reduced predation by the Pr. japonica lady beetle, and this response was more pronounced for lady beetle larvae than for adults. A field investigation showed that the species richness and quantity of lady beetle species in plots with fire ants were much lower than in those without fire ants. In an olfaction bioassay, lady beetles preferred to move toward untended rather than tended mealybugs. Overall, these results suggest that mutualism between S. invicta and P. solenopsis may have a serious impact on predation of P. solenopsis by lady beetles, which could promote growth of P. solenopsis populations.
Biological control of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) using entomopathogenic fungi is being studied as a viable control strategy. The efficacy of a Metarhizium anisopliae (Metschnikoff) Sorokin (Hypocreales: Clavicipitaceae)-based attractant—contaminant device (ACD) to control C. capitata was evaluated in a medium-scale (40 ha) 2-yr field trial using a density of 24 ACD per ha. Results showed that this density was adequate to efficiently reduce fruitfly populations and that the inoculation dishes (IDs) needed replacing mid-season to provide protection for the entire season. In this study, fungal treatment was even more effective than conventional chemical treatment. Population dynamics in fungus-treated fields along with the infectivity study of field-aged IDs in the laboratory found that the ACD remained effective for at least 3 mo. The results suggest M. anisopliae-based ACD can be used to control C. capitata in the field. The implications of its use, especially as a tool in an integrated pest management program, are discussed.
Beauveria bassiana Vuillemin and Metarhizium anisopliae (Metschnikoff) Sorokin are fungi with potential for controlling Musca domestica L. However, the impact on this dipteral may vary depending on the fungal isolates and the methodology used. This study evaluated the pathogenicity of direct application and horizontal transmission of B. bassiana (CG240) and M. anisopliae (CG34) on adult M. domestica individuals. The impact of B. bassiana and M. anisopliae on M. domestica was evaluated at the concentrations 2 × 104, 2 × 105, 2 × 106, and 2 × 107 conidia/ml. Horizontal transmission was also estimated between sexes at different infection periods of the vector insect. The mortality of adult M. domestica individuals directly infected with B. bassiana was above 90%, and the mortality of those infected with M. anisopliae ranged from 25.50 to 97.78%. Horizontal transmission of B. bassiana caused the death of 100% of individuals, in turn, that of M. anisopliae killed 55% of male and 100% of female individuals. Horizontal transmission of fungi was negatively influenced by time. This study shows the potential of these fungi for controlling M. domestica, both with the direct implementation strategy and horizontal transmission. However, field studies are needed to evaluate the capacity to decrease the M. domestica population using these alternatives.
Experimental and commercial preparations of Metarhizium brunneum (Petch) strain F52 were evaluated for control of Japanese beetle, Popillia japonica Newman (Coleoptera: Scarbaeidae), larvae (white grubs) in the laboratory and under field conditions. Experimental preparations consisted of granule and liquid formulations made using in vitro produced microsclerotia, which are intended to produce infective conidial spores after application. These formulations were compared against commercial insecticides (imidacloprid and trichlorfon), and commercial formulations of M. brunneum F52 (Met 52) containing only conidia. Field-collected grubs were susceptible to infection in a dosage-dependent relationship when exposed to potting soil treated with experimental microsclerotia granules in the laboratory. The LC50 for field-collected larvae was 14.2 mg of granules per cup (∼15 g granules/m2). Field plots treated with experimental and commercial formulations of M. brunneum F52 after 10 September (targeting second and third instar grubs) had significantly lower grub densities compared with untreated plots, providing 38.6–69.2% control, which sometimes equaled levels of control with chemical insecticides. Fungal treatments made prior to 21 August provided 14.3–69.3% control, although grub densities resulting from these treatments were often not significantly lower than those in untreated control plots. By comparison, chemical insecticide treatments provide 68–100% grub control, often providing better control when applied earlier in the season. In conclusion, P. japonica larvae are susceptible to infection by M. brunneum, and grub densities were reduced most consistently by fall applications targeting later instars.
DNA barcoding and morphological analyses of Korean Lymantria (Erebidae, Lepidoptera) were conducted for quarantine inspection. In DNA barcoding, Lymantria dispar identified through quarantine inspection was distinguished as three species, L. dispar asiatica, L. albescens, and L. xylina. Lymantria monacha, which is known as a single species in Korea, is revealed as containing three species, L. monacha, L. minomonis, and L. sugii. At the subspecies level, L. dispar dispar formed a single cluster, whereas L. d. asiatica and L. d. japonica formed a cluster containing both subspecies. In morphological re-examination on DNA barcoding results, L. dispar was distinguished from L. albescens by wing pattern, and from L. xylina by papillae anale. L. monacha and the related species were hard to be distinct from each other by using wing pattern, but it was easily distinct through comparison of genitalia. Therefore, DNA barcoding led to accurate identification in species level, but in subspecies level, only a taxon showing geographically far distance was discriminated from the others. These results may provide a taxonomic outline of the Korean Lymantria fauna and may be used as an identification reference for Lymantria species during quarantine inspection.
Solid male lure dispensers containing methyl eugenol (ME) and raspberry ketone (RK), or mixtures of the lures (ME RK), and dimethyl dichloro-vinyl phosphate (DDVP) were evaluated in area-wide pest management bucket or Jackson traps in commercial papaya (Carica papaya L.) orchards where both oriental fruit fly, Bactrocera dorsalis (Hendel), and melon fly, Bactrocera cucurbitae (Coquillett), are pests. Captures of B. dorsalis with fresh wafers in Jackson and bucket traps were significantly higher on the basis of ME concentration (Mallet ME [56%] > Mallet MR [31.2%] > Mallet MC [23.1%]). Captures of B. cucurbitae with fresh wafers in Jackson and bucket traps were not different regardless of concentration of RK (Mallet BR [20.1%] = Mallet MR [18.3%] = Mallet MC [15.9%]). Captures of B. dorsalis with fresh wafers, compared with weathered wafers, were significantly different after week 12; captures of B. cucurbitae were not significantly different after 16 wk. Chemical analyses revealed presence of RK in dispensers in constant amounts throughout the 16-wk trial. Degradation of both ME and DDVP over time was predicted with a high level of confidence by nonlinear asymptotic exponential decay curves. Results provide supportive data to deploy solid ME and RK wafers (with DDVP) in fruit fly traps for detection programs, as is the current practice with solid TML dispensers placed in Jackson traps. Wafers with ME and RK might be used in place of two separate traps for detection of both ME and RK responding fruit flies and could potentially reduce cost of materials and labor by 50%.
This laboratory-based study examined the effects of low-temperature phosphine fumigation on the survival of the eggs and larvae of the guava fruit fly, Bactrocera correcta (Bezzi). Individual flies at different developmental stages, from 6-h-old eggs to third instars, were exposed to 0.92 mg/liter phosphine for 1–7 d at 5°C. We found that 12-h-old eggs and third instars were the most tolerant to phosphine. Increasing phosphine concentrations from 0.46 to 4.56 mg/liter increased mortality in these two stages. However, increased exposure times were required to achieve equal mortality rates in 12-h-old eggs and third instars when phosphine concentrations were ≥4.56 and ≥3.65 mg/liter, respectively. Cnt = k expression was obtained at 50, 90, and 99% mortality levels, and the toxicity index (n) ranged from 0.43 to 0.77 for the two stages. The synergistic effects of a controlled atmosphere (CA) with elevated CO2 levels were also investigated, and we found that a CO2 concentration between 10% and 15% under CA conditions was optimal for low-temperature phosphine fumigation.
Light brown apple moth, Epiphyas postvittana (Walker), eggs were subjected to oxygenated phosphine fumigation treatments under 70% oxygen on cut flowers to determine efficacy and safety. Five cut flower species: roses, lilies, tulips, gerbera daisy, and pompon chrysanthemums, were fumigated in separate groups with 2,500 ppm phosphine for 72 h at 5°C. Egg mortality and postharvest quality of cut flowers were determined after fumigation. Egg mortalities of 99.7–100% were achieved among the cut flower species. The treatment was safe to all cut flowers except gerbera daisy. A 96-h fumigation treatment with 2,200 ppm phosphine of eggs on chrysanthemums cut flowers also did not achieve complete control of light brown apple moth eggs. A simulation of fumigation in hermetically sealed fumigation chambers with gerbera daisy showed significant accumulations of carbon dioxide and ethylene by the end of 72-h sealing. However, oxygenated phosphine fumigations with carbon dioxide and ethylene absorbents did not reduce the injury to gerbera daisy, indicating that it is likely that phosphine may directly cause the injury to gerbera daisy cut flowers. The study demonstrated that oxygenated phosphine fumigation is effective against light brown apple moth eggs. However, it may not be able to achieve the probit9 quarantine level of control and the treatment was safe to most of the cut flower species.
Monitoring population levels of the Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae), at the orchard level prior and during the fruit ripening period can result in significant savings in the costs of managing this pestiferous insect. Unfortunately, to date, no highly effective and economically viable trap is available to growers. To move toward this goal, trap—lure combinations were evaluated in trials performed in citrus orchards in Veracruz, Mexico. CeraTrap, an enzymatic hydrolyzed protein from pig intestinal mucose, was 3.6 times more attractive to A. ludens than the most commonly used bait of Captor (hydrolyzed protein and borax) when using Multilure traps. When several commercial traps were evaluated, the efficacy of a simple and inexpensive transparent polyethylene (PET) bottle with 10-mm lateral holes was similar to that of the costly Multilure trap when baited with CeraTrap and significantly more effective than a Multilure trap baited with Captor. PET bottles filled with Cera Trap, rebaited at 8-wk intervals, and tested in trials encompassing 72 ha of citrus groves, were significantly more effective than Multilure traps baited with Captor that need to be serviced weekly. In addition to this relevant finding, CeraTrap baited traps detected A. ludens at lower population densities and attracted a significantly higher number of flies at all densities when compared with Captor-baited traps.We conclude that CeraTrap represents a cost-effective and highly efficient bait that will enable us to pursue the goal of developing economic thresholds, a badly needed management tool for A. ludens.
Epiphyas postvittana (Walker) (light-brown apple moth) is a polyphagous herbivore of economic significance, which also feeds on Vitis vinifera L. The E. postvittana—V. vinifera interacting system also involves the participation of the fungus Botrytis cinerea Persoon ex Fries. We have been exploring the relationship among E. postvittana—V. vinifera—B. cinerea over the past two years. In this article, we report the preference and performance of the larvae of E. postvittana raised solely on a synthetic diet incorporated with the mycelial material of B. cinerea (Diet B). To characterize the effect of fungus on the development of E. postvittana, another synthetic diet was prepared that included the lyophilized leaf material of V. vinifera (Diet C). When raised on Diets B and C, a decrease in the duration of larval development and an increase in the survival and fecundity rate of E. postvittana occurred. Diet B influenced the pupal mass, but a significant increase occurred when the larvae were fed on Diet C. The larval emergence rate was the greatest in E. postvittana raised on Diet B, followed by those on Diet C. The F2 generation of the larvae reared on Diet B showed similar effects as F1 on the life-history performance of the larvae. Diet B enhanced the life-history performance of E. postvittana, although the larvae of E. postvittana showed little preference to Diet B. The greater fertility rate of E. postvittana reared on Diet B suggests the importance of sterols as shown in Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae) and in a few Myrmicinae (Hymenoptera: Formicidae), which serve as precursors to different ecdysteroids that regulate many critical processes through embryonic development.
Large citrus areas in Tamaulipas are affected by Anastrepha ludens (Loew) populations. Here we report the findings of a spatio-temporal analysis of A. ludens on an extended citrus area from 2008–2011 aimed at analyzing the probabilities of A. ludens infestation and developing an infestation risk classification for citrus production. A Geographic Information System combined with the indicator kriging geostatistics technique was used to assess A. ludens adult densities in the spring and fall. During the spring, our models predicted higher probabilities of infestation in the western region, close to the Sierra Madre Oriental, than in the east. Although a patchy distribution of probabilities was observed in the fall, there was a trend toward higher probabilities of infestation in the west than east. The final raster models summarized the probability maps using a three-tiered infestation risk classification (low-, medium-, and high risk). These models confirmed the greater infestation risk in the west in both seasons. These risk classification data support arguments for the use of the sterile insect technique and biological control in this extended citrus area and will have practical implications for the area-wide integrated pest management carried out by the National Program Against Fruit Flies in Tamaulipas, Mexico.
Egg cannibalism is common in Coccinellidae, but its biological consequences have not been fully explored.We examined egg cannibalism by neonates, fourth instars, and adults of Hippodamia convergens Guerin-Meneville for effects on development, reproduction, and progeny fitness. We also tested female adults for ability to avoid cannibalizing their own eggs and first-instar larvae, and both sexes for changes in cannibalism propensity following mating, all in the presence of ad libitum food [larvae: eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), adults: Schizaphis graminum (Rondani)]. Cannibalism by neonates reduced developmental time and increased male body size. Cannibalism in the fourth instar accelerated pupation and led to the production of eggs that hatched faster, regardless of which parent cannibalized. However, egg fertility was improved only by maternal cannibalism in the fourth instar. Females recognized their own egg clusters, sometimes added eggs to them, and preferentially cannibalized nonfilial clusters. Most gravid females cannibalized a first-instar larva within 30 min, whether filial or not. Adult egg cannibalism was similar for virgin males and females, but declined after mating in males, and increased in females, although it had no effect on fecundity or fertility. Daughters of cannibal pairs were heavier than those of other mating combinations, but offspring of noncannibal parents had the fastest development. Reproductive females appeared to use egg cannibalism to reduce risk for their own eggs, increasing the number cannibalized with the number laid. Thus, egg cannibalism in coccinellids varies with life stage, sex, and reproductive condition, independent of food availability, and benefits are life stage specific.
The brown planthopper, Nilaparvata lugens (Stål), is a destructive insect pest on rice throughout Asia. As a visible genetic marker, red eye mutant colony of brown planthopper is a valuable material. Here, we established the near-isogenic lines, NIL-BB and NIL-rr, through mating red eye females to brown eye brothers for eight successive generations. Biological experiments showed that NIL-BB had big fitness cost; however, NIL-rr had comparable survival and fertility parameters with BB, a normal laboratory brown planthopper strain. Significantly lower number eggs per female and egg hatchability were the key factors resulting in big fitness cost of NIL-BB. The population trend indexes of BB, NIL-rr, and NIL-BB were 52.18, 43.80, and 4.19, respectively. Real-time PCR study suggested that the poorer fertility of NIL-BB was not mediated by the differential expression of genes relating to oogenesis. The stronger fitness of NIL-rr compared with NIL-BB may be caused by the eye mutant gene or its closely linked genes having stronger compensation ability for reproduction. The comparable fitness of NIL-rr with BB indicated that NIL-rr may be used in field research. The NIL-BB strain with significantly declined fecundity and survival ability can be used as study model for the signal pathways relating to fecundity.
Halyomorpha halys (Sta° l) is an invasive pest that attacks numerous crops. For growers to make informed management decisions against H. halys, an effective monitoring tool must be in place. We evaluated various trap designs baited with the two-component aggregation pheromone of H. halys and synergist and deployed in commercial apple orchards.We compared our current experimental standard trap, a black plywood pyramid trap 1.22 m in height deployed between border row apple trees with other trap designs for two growing seasons. These included a black lightweight coroplast pyramid trap of similar dimension, a smaller (29 cm) pyramid trap also ground deployed, a smaller limb-attached pyramid trap, a smaller pyramid trap hanging from a horizontal branch, and a semipyramid design known as the Rescue trap.We found that the coroplast pyramid was the most sensitive, capturing more adults than all other trap designs including our experimental standard. Smaller pyramid traps performed equally in adult captures to our experimental standard, though nymphal captures were statistically lower for the hanging traps. Experimental standard plywood and coroplast pyramid trap correlations were strong, suggesting that standard plywood pyramid traps could be replaced with lighter, cheaper coroplast pyramid traps. Strong correlations with small ground- and limb-deployed pyramid traps also suggest that these designs offer promise as well. Growers may be able to adopt alternative trap designs that are cheaper, lighter, and easier to deploy to monitor H. halys in orchards without a significant loss in sensitivity.
A new adult diet formulation was evaluated for sterile Anastrepha ludens (Loew) and Anastrepha obliqua (Macquart) males at the emergence and release facility of fruit flies in Mexico. The formulation consists of hydrolyzed protein, sugar, juvenile hormone analogue methoprene, and water. The proportion of the ingredients between the solute (4% hydrolyzed protein and 96% sugar) and solvent (10% methoprene and 90% water) was 5:1. This new formulation was called the 1:24 formulation. The main objectives of this study were to develop a simple way to supply the 1:24 formulation to adults and to compare the sexual performance of these flies with the performance of flies fed a standard diet (called the Mubarqui formulation) used at the emergence and release facility of fruit flies in Mexico. The preparation, time, and cost also were evaluated. The results showed no significant differences in the sexual behaviors of the males (number of males mating, number of males calling, mating latency, and mating duration) between the 1:24 formulation and the Mubarqui formulation. However, the cost and the required preparation time are much lower for the 1:24 formulation process than for the Mubarqui formulation process. Based on these results, we recommend the 1:24 formulation as an additional adult diet option in the handling of sterile flies. Its application is practical and does not require changes in packaging systems. The contribution of our findings and their potential application to the improvement of the sterile insect technique are discussed.
The ladybird Cheilomenes sexmaculata (F.) is an important aphidophagous predator in Asia. In order to mass rear predators for biological control, it is valuable to identify the features of populations that are affected by variations in field conditions. Life tables can provide comprehensive descriptions of the development, survival, and fecundity of a population. However, there are few life table studies of C. sexmaculata. Studies of life history have been carried out in many arthropods using the traditional female age-specific life table, which takes only female individuals into consideration, while the variations in developmental rates amongst individuals are ignored. In this paper, we constructed life tables for C. sexmaculata fed on Myzus persicae (Sulzer) both at constant temperature in the laboratory and fluctuating temperature in the greenhouse, and analyzed the data using the age-stage, two-sex life table. The bootstrap technique was used to estimate the standard errors of the population parameters. The results showed that preadult C. sexmaculata developed more slowly and had lower survival and reproductive rates under greenhouse conditions, as indicated by the curves of age-stage survival rate (sxj), age-stage-specific fecundity (fxj) of the female stage, age-specific fecundity (mx), and age-specificmaternity (lxmx). Our results also showed that the intrinsic rate of increase (r), net reproductive rate (R0), and finite rate of increase (λ) under laboratory and greenhouse conditions were 0.1668 d-1 and 0.1027 d-1, 192.1 and 53.0, and 1.1815 d-1 and 1.1082 d-1, respectively. Our results revealed significantly different life table parameters for C. sexmaculata under laboratory and greenhouse conditions. This information will be useful for developing a successful mass-rearing programfor C. sexmaculata for use in biological control.
Accurate assessment of insect pest establishment risk is needed by national plant protection organizations to negotiate international trade of horticultural commodities that can potentially carry the pests and result in inadvertent introductions in the importing countries. We used mechanistic and correlative niche models to quantify and map the global patterns of the potential for establishment of codling moth (Cydia pomonella L.), a major pest of apples, peaches, pears, and other pome and stone fruits, and a quarantine pest in countries where it currently does not occur. The mechanistic model CLIMEX was calibrated using species-specific physiological tolerance thresholds, whereas the correlative model MaxEnt used species occurrences and climatic spatial data. Projected potential distribution from both models conformed well to the current known distribution of codling moth. None of the models predicted suitable environmental conditions in countries located between 20°N and 20°S potentially because of shorter photoperiod, and lack of chilling requirement (<60 d at ≤10°C) in these areas for codling moth to break diapause. Models predicted suitable conditions in South Korea and Japan where codling moth currently does not occur but where its preferred host species (i.e., apple) is present. Average annual temperature and latitude were the main environmental variables associated with codling moth distribution at global level. The predictive models developed in this study present the global risk of establishment of codling moth, and can be used for monitoring potential introductions of codling moth in different countries and by policy makers and trade negotiators in making science-based decisions.
McPhail type traps are commonly used to catch tephritid pests using liquid baits as attractants. Unfortunately, these traps allow that some flies escape after feeding on the bait. Recently, a long-lasting and nontoxic enzymatic-hydrolyzed protein, known commercially as CeraTrap, has been introduced as a novel liquid bait. Because feeding on hydrolyzed proteins can improve reproduction in many tephritids, questions remain as to whether CeraTrap could provide a nutritious meal to flies that ingest the bait but escape the trap. In this study, we analyzed the efficacy of CeraTrap baited traps in capturing Anastrepha ludens flies of two different physiological states and two different diets. We also explored the effect of feeding on CeraTrap on the mating performance of males, ovarian development and fecundity of females and fly survival. Results demonstrated that CeraTrap attracted more proteindeprived and immature flies of both sexes and 2–30% of flies that entered the trap managed to escape. However, after feeding on the bait for 24 h, males exhibited lower mating success, longer latency to mate and longer copula durations than males fed on either sugar or sugar protein. Interestingly, females fed CeraTrap for 24 h developed ovaries as large as those females fed on sugar protein, however, they laid no eggs. When feeding continuously on CeraTrap, flies exhibited shorter lifespans and females laid no eggs. These findings indicate that, although some flies can ingest the bait and escape from the trap, their reproductive traits are negatively affected.
Western bean cutworm, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), is a native, univoltine pest of corn and dry beans in North America. The current degree-day model for predicting a specified percentage of yearly moth flight involves heat unit accumulation above 10°C after 1 May. However, because the moth's observed range has expanded into the northern and eastern United States, there is concern that suitable temperatures before May could allow for significant S. albicosta development. Daily blacklight moth catch and temperature data from four Nebraska locations were used to construct degree-day models using simple or sine-wave methods, starting dates between 1 January and 1 May, and lower (-5 to 15°C) and upper (20 to 43.3°C) developmental thresholds. Predicted dates of flight from these models were compared with observed flight dates using independent datasets to assess model performance. Model performance was assessed with the concordance correlation coefficient to concurrently evaluate precision and accuracy. The best model for predicting timing of S. albicosta flight used simple degree-day calculations beginning on 1 March, a 3.3°C (38°F) lower threshold, and a 23.9°C (75°F) upper threshold. The revised cumulative flight model indicated field scouting to estimate moth egg density at the time of 25% flight should begin when 1,432 degree-days (2,577 degree-days °F) have accumulated. These results underscore the importance of assessing multiple parameters in phenological models and utilizing appropriate assessment methods, which in this case may allow for improved timing of field scouting for S. albicosta.
Sleeve and large field cage experiments were conducted in Stoneville, MS, in 2010 and 2011 to assess adult rice stink bug, Oebalus pugnax (F.), injury in rice. ‘Cocodrie' and ‘Wells' were infested at bloom, milk, and soft dough stages of panicle development. Twenty rice panicles were infested individually in the sleeve cage experiment as replicates with 0, 1, or 2 O. pugnax in a split-plot, completely randomized design. The large cage experiment had four replications infested with 9 or 18 O. pugnax per square meter over multiple rice panicles in a split-plot, randomized complete block design per cultivar. Caged uninfested controls were included in each experiment. Rough rice yield and percentage of clean, damaged, and blank kernels were evaluated. In both experiments, stage of panicle development impacted grain yield and quality. Yield loss was greatest during the bloom stage, while kernel damage was greatest during the milk and soft dough stages. Rice yield decreased with increased infestation density. Kernel damage increased with increased infestation density. Blank kernels affect yield, while kernel damage affects grain quality. While grain yield is the bottom line, grain quality affects marketability, which directly affects yield profitability. Based on these results, this study considers O. pugnax injury significant in all three stages of panicle development and concludes that a more aggressive threshold is recommended from panicle emergence through soft dough. More research is needed to determine the specific threshold, but it appears to be lower than the current threshold of 5 per 10 sweeps.
The economic injury level for potato leafhopper, Empoasca fabae (Harris), in alfalfa (Medicago sativa L.) was developed over 30 yr ago. In response to increasing market value of alfalfa, farmers and consultants are interested in reducing the economic threshold for potato leafhopper in alfalfa. To address this question, caged field trials were established on two consecutive potato leafhopper susceptible crops in 2013. Field cages were infested with a range of potato leafhopper densities to create a linear regression of alfalfa yield response. The slopes, or yield loss per insect, for the linear regressions of both trials were used to calculate an economic injury level for a range of current alfalfa market values and control costs. This yield—loss relationship is the first quantification that could be used to help assess whether the economic threshold should be lowered, given the increased market value of alfalfa.
Seed-applied insecticides are the standard control method used in the United States to minimize rice water weevil (Lissorhoptrus oryzophilus Kuschel) injury to rice (Oryza sativa L.) roots, and often results in greater yields than rice that receives no seed-applied insecticide. Yield increases from seed-applied insecticides often occur even when insect pressure is low and should not cause yield loss. The research objective was to evaluate the effect of urea-nitrogen rate and seed-applied insecticide on number of rice water weevil larvae, nitrogen uptake, and rice grain yield. Six trials were conducted at the Pine Tree Research Station (PTRS) and the Rice Research Extension Center (RREC) to examine the response of rice plants receiving different insecticide-seed treatments and urea-nitrogen rate combinations. Insecticide-seed treatments included label rates of clothianidin, thiamethoxam, and a noinsecticide (fungicide only) control, in combination with season-total nitrogen rates of 0, 50, 100, 150, and 200 kg urea-nitrogen/ha. Rice seed that was treated with clothianidin or thiamethoxam generally had equal numbers of rice water weevil larvae, which were significantly fewer compared with rice that received no insecticide with an equivalent urea-nitrogen rate. Nitrogen uptake at panicle differentiation was not affected by insecticide-seed treatments at four of six sites and usually increased positively and linearly as urea-nitrogen rate increased. As urea-nitrogen rate increased, grain yield increased either linearly or nonlinearly. Averaged across urea-nitrogen rates, both insecticide seed treatments had similar yields that were 4 to 7% greater than the grain yields of rice that received no insecticide at four of the five harvested sites.
The redbanded stink bug, Piezodorus guildinii Westwood (Hemiptera: Pentatomidae), has recently emerged as a serious pest of soybean in the southern United States. Field cage studies were conducted to determine the response of R2 to R6 stage soybean to P. guildinii infestation. Soybean at R2 to R6 stages was infested with zero, one, two, and four P. guildinii adults per 0.3 m for 10 d using cylindrical wire mesh cages. Plant response was measured in terms of number of flat pods, seed yield, test weight, and number of seeds per pod. Results from a 2012 study showed significant yield reduction in response to P. guildinii infestations during the R3 to R6 stages. While results from a similar 2013 study showed a significant yield reduction only when R5 and R6 stage soybean were infested. Decrease in yield was owing to the combination of reduced seed weight and increased numbers of flat pods as a result of P. guildinii infestation. In addition, a field experiment was conducted to determine if flat pods are localized to the regions of P. guildinii feeding. Adults were confined to certain portions of plants (bottom, top, and both) using specially designed cages isolating these portions of the plants. Results from this experiment showed a significantly higher percentage of flat pods on plant portions infested with P. guildinii than those kept free of P. guildinii infestation, indicating that flat pods are the result of direct P. guildinii damage and are localized to the area of P. guildinii feeding.
In China, Adelphocoris lineolatus (Goeze) (Hemiptera: Miridae) is an important pest of alfalfa, cotton, and other crops, while Peristenus spretus (Chen & van Achterberg) (Hymenoptera: Braconidae) is the dominant nymphal parasitoid of this mirid bug. In the present study, the toxicity of 17 common insecticides to A. lineolatus was evaluated, and the susceptibility of P. spretus to the insecticides with high toxicity to A. lineolatus was tested under laboratory conditions. Of the 17 insecticides tested, 12 (beta cypermethrin, deltamethrin, carbosulfan, acetamiprid, emamectin benzoate, imidacloprid, phoxim, chlorpyrifos, acephate, profenophos, hexaflumuron, and abamectin) had a highly toxic effect on second-instar nymphs of A. lineolatus, with LC50 values ranging from 0.58 to 14.85 mg a.i. (active ingredient) liter-1. Adults of P. spretus were most sensitive to chlorpyrifos, with LC50 values of 0.03 mg a.i. liter-1, followed by phoxim, acetamiprid, profenophos, carbosulfan, acephate, deltamethrin, emamectin benzoate, imidacloprid, beta-cypermethrin, and abamectin, with LC50 values ranging from 0.06 to 3.09, whereas hexaflumuron exhibited the least toxicity to the parasitoid, with LC50 values >500 mg a.i. liter-1. A risk quotient analysis indicated that beta-cypermethrin, emamectin benzoate, abamectin, and hexaflumuron when applied against A. lineolatus were the least toxic to P. spretus.
Soil-dwelling insects are severe pests in many agroecosystems. These pests have cryptic life cycles, making sampling difficult and damage hard to anticipate. The management of soil insects is therefore often based on preventative insecticides applied at planting or cultural practices. Wireworms, the subterranean larvae of click beetles (Coleoptera: Elateridae), have re-emerged as problematic pests in cereal crops in the Pacific Northwestern United States. Here, we evaluated two management strategies for wireworms in long-term field experiments: 1) treating spring wheat seed with the neonicotinoid thiamethoxam and 2) replacing continuous spring wheat with a summer fallow and winter wheat rotation. Separate experiments were conducted for two wireworm species—Limonius californicus (Mannerheim) and Limonius infuscatus (Motschulsky). In the experiment with L. californicus, spring wheat yields and economic returns increased by 24–30% with neonicotinoid treatments. In contrast, in the experiment with L. infuscatus, spring wheat yields and economic returns did not increase with neonicotinoids despite an 80% reduction in wireworms. Thus, the usefulness of seed-applied neonicotinoids differed based on the wireworm species present. In experiments with both species, we detected significantly fewer wireworms with a no-till summer fallow and winter wheat rotation compared with continuous spring wheat. This suggests that switching from continuous spring wheat to a winter wheat and summer fallow rotation may aid in wireworm management. More generally, our results show that integrated management of soildwelling pests such as wireworms may require both preventative insecticide treatments and cultural practices.
Cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is a common pest of cotton throughout much of the world. In the United States, insecticide applications targeting cotton aphid in cotton are common in the Mid-South, Texas, and California. Cotton aphid population dynamics data were collected from eight insecticide efficacy trials conducted in Lubbock, TX, over a 4-yr period. Among the field populations in the nontreated plots, the instantaneous rate of population growth averaged 0.56 ± 0.608, and the mean population doubling time was 3.97 ± 2.16 d. For calculating economic injury levels (EIL) and thresholds, control costs were set at US$30.50/ha, market prices were evaluated at US$0.88, US$1.33, US$1.77, and US$2.21 kg-lint, and cotton yield potentials were evaluated at 672, 896, and 1,120 kg-lint/ha. The EIL we calculated ranged from 66 to 272 aphids per leaf, and averaged 137 aphids per leaf. Economic thresholds (ET) were calculated based on lead times of 1, 3, 5, and 7 d before EIL occurs. The mean ET across control cost, market price, and yield potential were 110 ± 48, 70 ± 31, 45 ± 19, and 29 ± 13 aphids per leaf at lead times of 1, 3, 5, and 7 d, respectively. Most curative pest management tactics in cotton are implemented within 3 d of determining need, and the ET at 3 d that we calculated (70 ± 31 aphids per leaf) overlaps the current recommended action threshold in Texas and California of 50 aphids per leaf.
Recent populations of the red sunflower seed weevil, Smicronyx fulvus LeConte (Coleoptera: Curculionidae), have been inconsistent or declining, particularly in North Dakota. Consequently, research on weevil biology, including development of resistant germplasm, has been limited. To determine whether cold storage of diapausing larvae could be improved, nonconstant temperature treatments (fluctuating thermal regime [FTR] and thermoperiod [TP]) were tested versus a constant 6°C for storage up to 365 d. Both alternate temperature treatments produced more adult weevils than constant 6°C for short (42, 91 d) storage, while all temperature treatments were good (≥60% adult emergence) at moderate term (182 d) cold storage, and FTR was best for long (365 d) periods. Excluding the 14-d storage period, which produced too few weevils for comparison, each doubling of cold storage time (e.g., from 42 to 91 d, 91 to 182 d), usually decreased the number of days to 50% relative emergence by ∼10 d. After 365 d of larval storage, emerged S. fulvus adults successfully infested sunflowers in a plant growth chamber, with damage per female similar to that observed in field trials. Compared with previous efforts to store weevil larvae, the method of collection and FTR storage is either more effective (greater adult emergence and reduced parasitism) or more time-efficient, and should permit year-round research using S. fulvus adults. Because successful emergence under FTR was >75% after 365 d, additional research would be required to determine the maximum effective duration of cold storage for S. fulvus.
In light of population declines of honey bees (Apis mellifera L.), research has refocused attention on alternative pollinators and their potential to fulfill pollination services within economically important agricultural crops. Bumble bees are one such alternative, and within the past 20 yr, these pollinators have been reared and sold as commercial pollinators. Investigation into their use has been limited and more research is needed to improve pollinator effectiveness in field settings. Quad pollination units of the commercially reared native bumble bee species, the common eastern bumble bee (Bombus impatiens Cresson), were monitored and evaluated for productivity during peak watermelon [Citrullus lanatus (Thunberg) Matsumura & Nakai] bloom in southern Delaware. Differing colony exposures including various shade structure designs and natural shade were compared to assess the quality of the shade in regards to bumble bee activity during watermelon bloom. Quads receiving different nest treatments were evaluated on the basis of foraging activity and colony weight gain. Results indicated that colonies within quads provided with artificial or natural shade had significantly more foraging activity, weighed more, and produced more cells than colonies in quads placed in the field with no shade. Colonies within quads provided with artificial and natural shade peaked later in terms of foraging and weight gain, suggesting that growers could extend harvest to take advantage of later markets and possible movement into fields that were planted later.
The kudzu bug, Megacopta cribraria (F.), first discovered in the United States in 2009, has rapidly become a pest of commercial soybean, Glycine max (L.) Merrill, throughout much of the southeast. Because of its recent arrival, management practices and recommendations are not well established. To develop action thresholds, we evaluated insecticide applications targeted at different densities of adults and nymphs determined using the standard 38-cm diameter sweep net sampling method in 12 soybean field trials conducted in Georgia, North Carolina, and South Carolina from 2011 to 2013. Average peak densities of M. cribraria in the untreated controls reached as high as 63.5 ± 11.0 adults per sweep and 34.7 ± 8.0 nymphs per sweep. Insecticide applications triggered at densities of one adult or nymph of M. cribraria per sweep, two adults or nymphs per sweep, and one adult or nymph per sweep, with nymphs present, resulted in no yield reductions in most cases compared with plots that were aggressively protected with multiple insecticide applications. A single insecticide application timed at the R3 or R4 soybean growth stages also resulted in yields that were equivalent to the aggressively protected plots. Typically, treatments (excluding the untreated control) that resulted in fewer applications were more cost-effective. These results suggest that a single insecticide application targeting nymphs was sufficient to prevent soybean yield reduction at the densities of M. cribraria that we observed.
Monochamus saltuarius Gebler is a vector that transmits the pine wood nematode, Bursaphelenchus xylophilus, to Korean white pine, Pinus koraiensis, in Korea. To reduce the damage caused by this nematode in pine forests, timely control measures are needed to suppress the cerambycid beetle population. This study sought to construct a forecasting model to predict beetle emergence based on spring temperature. Logs of Korean white pine were infested with M. saltuarius in 2009, and the infested logs were overwintered. In February 2010, infested logs were then moved into incubators held at constant temperature conditions of 16, 20, 23, 25, 27, 30 or 34°C until all adults had emerged. The developmental rate of the beetles was estimated by linear and nonlinear equations and a forecasting model for emergence of the beetle was constructed by pooling data based on normalized developmental rate. The lower threshold temperature for development was 8.3°C. The forecasting model relatively well predicted the emergence pattern of M. saltuarius collected from four areas in northern Republic of Korea. The median emergence dates predicted by the model were 2.2–5.9 d earlier than the observed median dates.
In 2007–2008, we examined the flight responses of wood-boring beetles (Coleoptera: Cerambycidae and Buprestidae) to multiple-funnel traps baited with the pine volatiles, ethanol, and α-pinene [85% (—)], and the bark beetle pheromones, racemic ipsenol and racemic ipsdienol. Experiments were conducted in mature pine stands in Canada (Ontario and New Brunswick) and the United States (Arkansas, Florida, Michigan, New Hampshire, North Carolina, Ohio, Tennessee, and Wisconsin). At each location, traps were deployed in 10 replicate blocks of four traps per block. The trap treatments were: 1) blank control; 2) ipsenol and ipsdienol; 3) ethanol and α-pinene; and 4) a quaternary blend of ipsenol, ipsdienol, ethanol, and α-pinene. Traps baited with the quaternary blend caught the greatest numbers of Acanthocinus nodosus (F.), Acanthocinus obsoletus (Olivier), Acmaeops proteus (Kirby), Astylopsis sexguttata (Say), Rhagium inquisitor (L.) (Cerambycidae), and Buprestis lineata (F.) (Buprestidae). Traps baited with ethanol and α-pinene caught the greatest numbers of Arhopalus rusticus (LeConte), Asemum striatum (L.), Tetropium spp., Xylotrechus sagittatus (Germar) (Cerambycidae), and Buprestis maculipennis Gory (Buprestidae) with minimal interruption by ipsenol and ipsdienol. Our results suggest that multiple-funnel traps baited with the quaternary lure blend of ipsenol, ipsdienol, ethanol, and α-pinene are effective for trapping various species of wood-boring beetles in pine forests of eastern North America, and may have utility in detection programs for adventive species in North America and overseas.
Polyphagous shot hole borer (Euwallacea sp., Coleoptera: Curculionidae: Scolytinae) has recently invaded southern California. The beetle, along with its associated fungi, Fusarium euwallaceae, Graphium sp., and Acremonium sp., causes branch dieback and tree mortality in a large variety of tree species including avocado (Persea americana Mill.) and box elder (Acer negundo L.). With the spread of the beetle through Los Angeles, Orange, and San Diego Counties in California, there is increasing concern that felled trees and pruned branches infested with polyphagous shot hole borer should receive sanitation treatment to reduce the potential spread of the beetle from the movement of untreated wood.We tested two sanitation methods to reduce beetle populations, chipping with a commercial chipper and solarization by covering logs with clear or black plastic in full sun. Both chipping and solarization decreased beetle emergence and boring activity compared to untreated control logs. Chipping was most effective for chip sizes <5 cm. Solarization was most effective using clear polyethylene sheeting during hot summer months, particularly August, when daily maximum temperatures were ≥35°C. Beetles persisted for 2 mo or more when solarization was applied during the spring or fall.
Many species of cerambycid beetles in the subfamily Cerambycinae are known to use male-produced pheromones composed of one or a few components such as 3-hydroxyalkan-2-ones and the related 2,3-alkanediols. Here, we show that this pheromone structure is characteristic of the cerambycine genus Neoclytus Thomson, based on laboratory and field studies of 10 species and subspecies. Males of seven taxa produced pheromones composed of (R)-3-hydroxyhexan-2-one as a single component, and the synthetic pheromone attracted adults of both sexes in field bioassays, including the eastern North American taxa Neoclytus caprea (Say), Neoclytus mucronatus mucronatus (F.), and Neoclytus scutellaris (Olivier), and the western taxa Neoclytus conjunctus (LeConte), Neoclytus irroratus (LeConte), and Neoclytus modestus modestus Fall. Males of the eastern Neoclytus acuminatus acuminatus (F.) and the western Neoclytus tenuiscriptus Fall produced (2S,3S)-2,3-hexanediol as their dominant or sole pheromone component. Preliminary data also revealed that males of the western Neoclytus balteatus LeConte produced a blend of (R)-3-hydroxyhexan-2-one and (2S,3S)-2,3-hexanediol but also (2S,3S)-2,3-octanediol as a minor component. The fact that the hydroxyketone-hexanediol structural motif is consistent among these North American species provides further evidence of the high degree of conservation of pheromone structures among species in the subfamily Cerambycinae.
The primary Lepidoptera pests of sweet corn (Zea mays L. convar. saccharata) in Georgia are the corn earworm, Helicoverpa zea (Boddie), and the fall armyworm, Spodoptera frugiperda (J. E. Smith). Management of these pests typically requires multiple insecticide applications from first silking until harvest, with commercial growers frequently spraying daily. This level of insecticide use presents problems for small growers, particularly for “pick-your-own” operations. Injection of oil into the corn ear silk channel 5–8 days after silking initiation has been used to suppress damage by these insects. Initial work with this technique in Georgia provided poor results. Subsequently, a series of experiments was conducted to evaluate the efficacy of silk channel injections as an application methodology for insecticides. A single application of synthetic insecticide, at greatly reduced per acre rates compared with common foliar applications, provided excellent control of Lepidoptera insects attacking the ear tip and suppressed damage by sap beetles (Nitidulidae). While this methodology is labor-intensive, it requires a single application of insecticide at reduced rates applied ∼2wk prior to harvest, compared with potential daily applications at full rates up to the day of harvest with foliar insecticide applications. This methodology is not likely to eliminate the need for foliar applications because of other insect pests which do not enter through the silk channel or are not affected by the specific selective insecticide used in the silk channel injection, but would greatly reduce the number of applications required. This methodology may prove particularly useful for small acreage growers.
Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is an invasive pest recently reported in Europe whose spread into new areas has caused severe economic damage to many agricultural crops. There are serious concerns about the currently available chemical insecticides because of their low efficacy in controlling the species and their environmental impact; so, several studies have focused on environmentally safe strategies. The sterile insect technique (SIT), which requires colony maintenance in laboratory and production of large numbers of live animals, can be utilized in pest management programs and could be integrated with other control strategies if the potential risks associated with the rearing and maintenance of the insect line under laboratory conditions are given sufficient attention. In this regard, the ability to cryobiologically preserve such stocks would be of substantial value. Important prerequisites for long-term cryopreservation are determination of the embryonic stages, identification of specific embryonic stages, and knowledge of development time. This paper describes the main visible markers for the different stages of embryonic development and determines the timing of development at 25°C. D. suzukii embryogenesis lasts 23–25 h at 25°C and can be divided into 17 stages defined by specific morphological markers. The point at which 50% of embryos are at Stage 14 and 50% are at Stage 15, the most tolerant stages for cryopreservation treatment, as ascertained for Drosophila melanogaster Meigen in prior studies, is reached in 14–15 h. The efficiency of this procedure might be impaired by the retention of eggs in the oviducts, making it impossible to determine the stage of embryonic development for ∼25% of laid eggs.
Dasineura mali Kieffer (Diptera: Cecidomyiidae) is an important pest of young apple trees in New Zealand and a serious quarantine pest in Asia, Australia, and western United States. Platygaster demades Walker (Hymenoptera: Platygastridae) is a parasitoid of D. mali. The developmental period of the parasitoid is longer than that of D. mail, suggesting a possible asynchrony between the two species in the field. Prior to the present study, this parasitoid was considered laying eggs only in the host eggs. Here we carried out experiments in the laboratory and field to determine whether P. demades also parasitized other stages of the host and explain the recently observed high parasitism rate and parasitoid—host synchronization in the field.We demonstrated for the first time that P. demades explored and accepted both eggs and first-instar larvae of D. mali as hosts. This feature widens the phenological window for parasitization, allowing the parasitoid to continue laying eggs after D. mali eggs hatch, and contributes to the high within- and between-generation parasitism rate and synchronization of the two species. Therefore, the difference in developmental period between the pest and its parasitoid cannot simply be considered evidence of asynchrony between the two. The consistent superparasitism rate and progeny sex ratio regardless of host stage at parasitization detected in the present study may be attributed to the fact that P. demades eggs do not hatch until the host larvae reach the third instar (mature) and thus all parasitoid larvae feed on the third-instar larvae with similar quantity and quality of nutrition. The higher parasitism rate in eggs than in larvae may be due to higher larval defense ability against attack by and lower attractiveness to the parasitoid.
In the Mediterranean region, the use of small-mesh netting to protect horticultural crops is an effective sustainable tool against pests. But in tropical regions, because of high humidity under the net favoring fungal development, netting with a larger mesh size has to be used, protecting crops against lepidopteran pests but not against small pests such as hemipterans, thrips, and phytophagous mites. A combination of netting with a repellent or irritant product is one possible solution, but the desire to reduce the use of synthetic chemicals and mitigate resistance issues calls for a natural alternative. The objective of this study was to evaluate the repellent, irritant, and toxic effects of nets dipped in 20 different plant extracts on Bemisia tabaci (Gennadius) adults. The repellent effect of volatile compounds was evaluated using a still-air olfactometer. The irritant effect and toxicity were evaluated with a no-choice test in tubes separated into two parts by an impregnated net. Our results showed the seven most irritant and toxic products against B. tabaci were aframomum, cinnamon, geranium, dill, citronella, litsea, and savory. The most repellent were aframomum and lemongrass, although cinnamon, geranium, and savory were also repellent at higher doses. Effects varied with the plant extract and the concentration, and effects were independent of one another, i.e., an essential oil can be irritant but not repellent, suggesting that the repellent mechanism and that behind the irritant or toxic effects is not the same. The use of repellent compounds in combination with netting as new pest control strategy is discussed.
Brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is a highly polyphagous invasive insect pest from eastern Asia that feeds on numerous fruit, vegetable, and field crops. Four commercial vineyards in Virginia were sampled in 2012 and 2013 to study the basic biology, seasonality, and distribution pattern of H. halys in vineyards. At each vineyard, two blocks were selected. Weekly 3-min timed count visual samplings were performed in border and interior sections from late May until mid-September. Overwintering adult bugs were first detected in vineyards in May; however, the timing of first detection differed among vineyards. Egg masses were found primarily in June and July, and were usually found on the lower surface of grape leaves, although they were occasionally on the upper leaf surface, on the berry, or on the rachis. All developmental stages of H. halys were found in vineyards, suggesting that grape can serve as a reproductive host for H. halys. Substantial variation in H. halys densities was found among vineyards and throughout the growing season. The first instars were found on egg masses and after molting, dispersed throughout the grape vines. The date on which the first egg mass was collected was considered as a biofix. Based on a degree—day model, there were sufficient degree—days for completion of a generation in Virginia vineyards. Significantly higher numbers of H. halys were collected in border sections compared with interior sections. These results are discussed in relation to the potential pest status of H. halys in vineyards and implications for possible control strategies.
Infestation by blueberry gall midge, Dasineura oxycoccana Johnson, is common in northern highbush blueberries, but its effects on crop productivity are unknown. We examined whether infestation by blueberry gall midge reduces flower bud production when compared with uninfested shoots, and how infestation at different times affects the crop response. From the fall of 2009 to the spring of 2011, the number of flower buds on infested and uninfested shoots of blueberry bushes was counted and compared. Despite causing branching of vegetative growth, there was no significant effect of infestation on flower bud production. During the summer of 2010, damaged shoots were marked throughout the growing season in June, July, or August. The number of flower buds set per shoot declined with later infestation dates, and shoots damaged in August had significantly fewer buds than those damaged in June and July. We discuss the implications of these findings for management of blueberry gall midge in northern highbush blueberry.
The codling moth Cydia pomonella (L.) is a worldwide pest of pome fruit. A better understanding of oviposition site selection by this insect would help management of this pest in orchards. Oviposition site selection of codling moth was assessed by manipulative experiments and field survey. In addition, the temperatures of different sites were recorded. Neonate infestation and egg hatching were tested to evaluate the consequences of oviposition site selection. The percentage of eggs laid on the shady side of apple clusters was significantly higher than on the sunny side. How.ever, this was not influenced by leaf surface turning. Percentage of eggs on upper and lower leaf surfaces was significantly influenced by leaf surface turning. Percentage of eggs on the lower leaf surface was significantly higher than turned lower leaf surface (∼41.1% higher) and significantly higher (∼35.5%) on the turned upper leaf surface on than upper leaf surfaces. There was no significant difference in neonate infestation between leaves and fruit, as well as between the upper and lower leaf surfaces. Number of eggs hatching on the shady side of clusters was significantly higher than on the sunny side (56.3% higher). In both the manipulative experiment and field survey, codling moths did not choose the sites with the highest mean temperature, but chose sites suitable for egg development and hatching. This indicates that in the field codling moth, oviposition site selection is not strictly thermophilous, but they look for the lower leaf surface on the shady side, which benefits the offspring.
Atemoya is a hybrid between Annona squamosa L. and Annona cherimola Miller (Annonaceae) and has potential to be an important fruit crop in tropical and subtropical areas. A major impediment to fruit production is low fruit set due to inadequate pollinator visits, typically, by beetles in the family Nitidulidae. We used Universal moth traps to monitor the attractiveness of two commercially available Nitidulidae lures in combination with various food attractants, including raw bread dough, apple juice, and malta beverage, a soft drink by-product of the brewing process. The most commonly trapped beetles were, in order of decreasing frequency, Carpophilus dimidiatus (F.), Brachypeplus mutilatus Erichson, Urophorus humeralis (F.) (Coleoptera: Nitidulidae), and Europs fervidus Blatchley (Coleoptera: Monotomidae). All traps, except the unbaited control traps, caught beetles. In a previous study, we found that combining two commercial lures had a synergistic effect on the attraction of these beetle species. In this study, the addition of food attractants increased the number of beetles trapped compared with traps baited with only the commercial lures. Also, food attractants appear to be key in attracting U. humeralis; only one U. humeralis individual of the 206 caught during the experiment was trapped without a food attractant. The variation between the number of beetles caught in traps containing the same treatments was high and may explain the erratic results reported in other studies of pollination in Annona spp. The results are discussed with respect to the use of nitidulid lures and food attractants to increase fruit set in atemoya and other Annonaceae.
Eradication technologies are needed for urban and suburban situations, but may require different technologies from pest management in agriculture. We investigated mating disruption of a model moth species recently targeted for eradication in Californian cities, by applying dollops of SPLAT releasing a two-component sex pheromone of the light brown apple moth in 2-ha plots in low-density residential Perth, Australia. The pheromone technology was applied manually at ∼1.5 m height to street and garden trees, scrubs, and walls at 500 dollops per hectare of 0.8 g containing ∼80 mg active two-component pheromone. Catches of male moths were similar among all plots before treatment, but in treated areas (six replicates) pheromone trap catches were substantially reduced for up to 29 wk posttreatment, compared with untreated control plot catches (three replicates). The treatment with pheromone reduced catch to virgin females by 86% (P < 0.001) and reduced the occurrence of mating by 93%, compared with three equivalent untreated control plot catches (P < 0.001). Eradication programs are following an upward trend with globalization and the spread of invasive arthropods, which are often first detected in urban areas. Eradication requires a major increase in the communication distance between individuals, but this can be achieved using sex pheromone-based mating disruption technology, which is very benign and suitable for sensitive environments. The need for new socially acceptable tools for eradication in urban environments is likely to increase because of increasing need for eradications.
Western flower thrips, Frankliniella occidentalis (Pergande), is one of the most destructive insect pests of greenhouse production systems with the ability to develop resistance to a wide variety of insecticides. A common resistance management strategy is rotating insecticides with different modes of action. By incorporating entomopathogenic organisms (fungi and bacteria), which have discrete modes of action compared to standard insecticides, greenhouse producers may preserve the effectiveness of insecticides used for suppression of western flower thrips populations. The objective of this study was to determine how different rotation programs that include entomopathogenic organisms (Beauveria bassiana, Isaria fumosoroseus, Metarhizium anisopliae, and Chromobacterium subtsugae) and commonly used standard insecticides (spinosad, chlorfenapyr, abamectin, and pyridalyl) may impact the population dynamics of western flower thrips adult populations by means of suppression. Eight-week rotation programs were applied to chrysanthemum, Dendranthema x morifolium plants and weekly counts of western flower thrips adults captured on yellow sticky cards were recorded as a means to evaluate the impact of the rotation programs. A final quality assessment of damage caused by western flower thrips feeding on foliage and flowers was also recorded. Furthermore, a cost comparison of each rotation program was conducted. Overall, insecticide rotation programs that incorporated entomopathogenic organisms were not significantly different than the standard insecticide rotation programs without entomopathogenic organisms in suppressing western flower thrips adult populations. However, there were no significant differences among any of the rotation programs compared to the water control. Moreover, there was no differential effect of the rotation programs on foliage and flower quality. Cost savings of up to 34% (in US dollars) are possible when including entomopathogenic organisms in the rotation program. Therefore, by incorporating entomopathogenic organisms into insecticide rotation programs, greenhouse producers can decrease costs without affecting suppression, as well as diminish selection pressure on western flower thrips adult populations, which may avoid or delay resistance development.
Some exotic ambrosia beetles are damaging pests in ornamental nurseries. Xylosandrus germanus (Blandford) is the most problematic ambrosia beetle in Ohio nurseries. Movement of X. germanus in nurseries has not been characterized, and knowledge is lacking on whether infestations originate from within nurseries or surrounding habitats. Flight activity of X. germanus was monitored in nurseries and adjacent wooded areas to determine the source of beetles infesting nurseries, and characterize their movement within nurseries. Ethanol-baited bottle traps were positioned within wooded areas adjacent to commercial nurseries and within nurseries at various distances from the nursery woodlot interface. Flight activity of overwintered X. germanus occurred in wooded areas adjacent to nurseries before occurrence within nurseries. There was a direct relationship between degree-days and the distance from woodlots when X. germanus were first found in traps in spring, with earlier captures closest to wooded areas and latest ones furthest away into the nursery. X. germanus appeared to move into nurseries from adjacent wooded areas, with numbers trapped within nurseries decreasing with distance away from wooded areas. Trees in the interior of nurseries would appear to be subjected to less attack pressure than trees near the nursery border. Intercepting beetles as they move into nurseries might be an effective strategy to reduce attack pressure on valuable trees.
The black cutworm, Agrotis ipsilon Hufnagel, and fall armyworm, Spodoptera frugiperda Smith (Lepidoptera: Noctuidae), are common turfgrass pests of golf courses in the southeastern United States. Heat-tolerant bentgrass (Agrostis stolonifera L.) cultivars are expanding the range of bentgrass further south, but these cultivars have not been studied for their potential host plant resistance to black cutworm or fall armyworm. The goals of the study were to investigate feeding response of black cutworm and fall armyworm to these newer heat-tolerant creeping bentgrass cultivars, as well as commonly used cultivars of bermudagrass [Cynodon dactylon (Loppers.)]. Choice and no-choice feeding assays and fecundity tests were conducted in the laboratory and greenhouse to evaluate performance and preference of the two insects. When given a choice, neither black cutworm nor fall armyworm showed a preference for the majority of new cultivars tested. There were no differences in leaf area consumption or insect development for either pest in no-choice feeding assays. Black cutworm females preferred laying eggs in bentgrass compared with bermudagrass, but will oviposit onto bermudagrass, suggesting that both turf species are suitable hosts of this pest. The broad host ranges of generalist caterpillar pests of turfgrass hinder the application of host plant resistance in integrated pest management on golf courses.
Linepithema humile (Mayr), the Argentine ant, is an invasive pest that has spread throughout the United States and is a problem in natural and managed habitats in South Carolina. Foraging patterns and the effectiveness of liquid baits for control of this pest have been studied in urban areas. However, similar studies have not been conducted in natural areas such as parks, picnic grounds, or campsites. L. humile populations can be large and widespread, making them a major nuisance pest for visitors to these natural areas. The primary objective of this study was to determine an effective distance between bait stations for control of L. humile in a natural area. A double antibody-sandwich enzymelinked immunosorbent assay (DAS-ELISA) procedure was used to detect individual ants that consumed rabbit immunoglobin (IgG) protein for marking and tracking. In both lab and field conditions, there was a significant difference in the detection of IgG in ants fed protein marker mixed with sugar water compared with ants only fed sugar water. Additional field studies revealed that an individual ant could retain detectable levels of protein marker for 3 d and that an ant feeding on IgG containing bait could be detected over 15 m from the original bait source. Overall, we found that using liquid ant baits, with a placement of 20 m between stations, was effective in reducing L. humile numbers between April to October, 2012 in a natural park area of Lake Greenwood State Park, SC.
Describing desiccation stages based on the physical appearance of termites has not been evaluated previously. Formosan subterranean termites were studied to determine the rate of water loss, singly and in groups, in the laboratory. The stages of water loss are described based on changes in physical appearance and percent total body water loss evaluated at 2- to 8-h time intervals up to 32 h.Workers in groups lost water slower than individual worker trials. Weight loss was linear over time for worker groups and individuals, as was individual soldier only trials. Water loss in individual workers was significantly faster than in soldiers. Three physical stages of desiccation are described for living workers: (I) curling of antennae, (II) on back but with assistance able to right themselves and walk, and (III) unable to get off back; and two stages for living soldiers (II and III). Recovery was determined from termites in a second trial by transferring stage I, II, and III individuals from open, dry Petri dishes to those with moist filter paper at 4, 6, 10, 12, 14, 16, 24, 26 and 28 h. After 12 h on moist filter paper, stage I workers had a 83% recovery rate, stage II had a 33%, and stage III had a 7% recovery. Soldiers had a 56% recovery at stage II and was similar to the recovery of workers at stage III. Most termites that reached stage III were destined to die.
The diamondback moth, Plutella xylostella (L.), is considered one of the most damaging lepidopteran pests, and it has developed resistance to all conventional insecticide classes in the field. Chlorantraniliprole is the first commercial insecticide that belongs to the new chemical class of diamide insecticides. But, P. xylostella have already shown resistance to chlorantraniliprole in China. After 52 generations of selection with chlorantraniliprole, ∼48.17-fold resistance was observed. The resistant strain showed cross-resistance to flubendiamide (7.29-fold), abamectin (6.11-fold), and cyantraniliprole (3.31-fold). Quantitative real-time polymerase chain reaction analysis showed that the expression of the ryanodine receptor gene was higher in the resistant strain than that in the susceptible strain. Enzyme assays indicated that cytochrome P450 activity in the resistant strain was 4.26 times higher compared with the susceptible strain, whereas no difference was seen for glutathione-S-transferase and esterase. Moreover, the toxicity of chlorantraniliprole in the resistant strain could be synergized by piperonyl butoxide, but not by diethyl maleate, and S,S,S-tributyl phosphorothioate. These results can serve as an important base for guiding the use of insecticide in field and delaying the development of pests that are resistant to the insecticides.
Western corn rootworm, Diabrotica virgifera virgifera LeConte, is a major pest of corn, Zea mays L. The effect of the Bt proteins Cry34/35Ab1 and Cry3Bb1, alone or pyramided in corn hybrids on D. v. virgifera adult emergence was evaluated in field experiments for 3 yr. Experiments were infested artificially with 2,500 viable D. v. virgifera eggs per row meter of corn. The reduction in beetle emergence compared with non-Bt controls, from Cry34/35Ab1, Cry3Bb1, and the pyramided hybrids ranged from 64.3 to 97.4%, 91.1 to 95.2%, and 98.1 to 99.6%, respectively. The sex ratio of emerged beetles was usually female-biased from the Cry3Bb1 and pyramided treatments, but not from Cry34/35Ab1 treatment alone. Emergence from all Bt hybrids was delayed compared with the control, with the delay longest from the pyramided hybrid. In 2013, three egg infestation levels were tested, with densitydependent mortality observed at 1,250 viable eggs per row meter. The effect of Bt proteins on the emergence timing and sex ratio of D. v. virgifera may impact the suitability of resistance management plans, specifically the effectiveness of the refuge strategy. Susceptible males emerging from refuge might not be synchronized to mate with potentially resistant females emerging later from Bt corn hybrids.
Insecticide resistance in the lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), can pose a serious threat to their successful management in broiler chicken farms in Arkansas. Resistance and cross-resistance were determined in lesser mealworm populations collected from two broiler farms in Arkansas, with different insecticide application histories. Farm M was treated with insecticides over the past 10 yr, whereas Farm S had no insecticidal usage history. Concentration—mortality bioassays using selected insecticides were conducted on adults and seventh-instar larval beetles. A probit analysis suggested the M population to be resistant to cyfluthrin and tetrachlorvinphos, while the S population was susceptible to both compounds. The M population showed no crossresistance to imidacloprid, spinosad, or chlorfenapyr. TheMand S populations were similar in their susceptibility to imidacloprid, spinosad, and chlorfenapyr. The suitability of imidacloprid and spinosad, and further testing of chlorfenapyr as a potential candidate for lesser mealworm control is discussed.
The western flower thrips is an economically important worldwide pest of many crops, and chlorpyrifos has been used to control western flower thrips for many years. To develop a better resistance- management strategy, a chlorpyrifos-resistant strain of western flower thrips (WFT-chl) was selected in the laboratory. More than 39-fold resistance was achieved after selected by chlorpyrifos for 19 generations in comparison with the susceptible strain (WFT-S). Proteome of western flower thrips (WFT-S and WFT-chl) was investigated using a quantitative proteomics approach with isobaric tag for relative and absolute quantification technique and liquid chromatography-tandem mass spectrometry technologies. According to the functional analysis, 773 proteins identified were grouped into 10 categories of molecular functions and 706 proteins were presented in 213 kinds of pathways. Comparing the proteome of WFT-chl with that of WFT-S, a total of eight proteins were found up-regulated and three down-regulated. The results from functional annotation and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses indicated that the differentially expressed protein functions in binding, catalyzing, transporting, and enzyme regulation were most important in resistance development. A list of proteins functioning in biological processes of metabolism, biological regulation, and response to stimulus was found in WFT-chl, suggesting that they are possibly the major components of the resistance mechanism to chlorpyrifos in western flower thrips. Notably, several novel potential resistance-related proteins were identified such as ribosomal protein, Vg (vitellogenin), and MACT (muscle actin), which can be used to improve our understanding of the resistance mechanisms in western flower thrips. This study provided the first comprehensive view of the complicated resistance mechanism employed by WFT-S and WFT-chl through the isobaric tag for relative and absolute quantification coupled with liquid chromatography-tandem mass spectrometry technologies.
Paichongding is an adicyclicnitromethylene neonicotinoid insecticide with a cis-configuration. Bioassay of paichongding was conducted against Nilaparvata lugens Stål under a laboratory condition. Mortality of N. lugens was analyzed by time—concentration—mortality (TCM) regressions based on the complementary log-log (CLL) model. The conditional mortalities of test individuals increased with the exposure time after treatments with different concentrations, showing that the speed of insecticidal action is concentration dependent. Meanwhile, the conditional mortalities of N. lugens increased as the concentrations of paichongding increased for all developmental stages from instars I-II to macropterous females. Correspondingly, LC50 and LC90 values to N. lugens gradually decreased with the developmental stages, in which instars I-II were the most sensitive to paichongding, with LC50 values of 6.31, 0.45, 0.09, and 0.03 mg/liter for 24, 48, 72, and 96 h after treatments, respectively, while macropterous females were the least sensitive among all developmental stages, with LC50 values of 309.03, 11.48, 1.35, and 0.19 mg/liter at 24, 48, 72, and 96 h after the treatments, respectively. The time—concentration—mortality modeling was mathematically and biologically robust to evaluate the effects of paichongding on N. lugens. The results suggest that paichongding would be an effective alternative pesticide for controlling N. lugens considering its potent effects.
Beet armyworm, Spodoptera exigua (Hübner), is a worldwide pest of many crops. Chemical insecticides are heavily used for its control in China, and serious resistance has been evolved in the field to a variety of insecticides including emamectin benzoate. Through repeated backcrossing to a susceptible strain (WH-S) and selection with emamectin benzoate, the trait conferring resistance to emamectin benzoate in a field-collected population of S. exigua (moderately resistant to emamectin benzoate and strongly resistant to pyrethroids and indoxacarb) was introgressed into WH-S to generate a near-isogenic resistant strain (WH-EB). Compared with WH-S, the WH-EB strain developed a 1,110-fold resistance to emamectin benzoate and a high level of cross-resistance to abamectin (202-fold), with low levels of cross-resistance to cypermethrin (10-fold) and chlorfluazuron (7-fold), but no crossresistance to representatives of another six different classes of insecticides (chlorantraniliprole, chlorfenapyr, indoxacarb, spinosad, tebufenozide, and chlorpyrifos). Resistance to emamectin benzoate in WH-EB was autosomal, incompletely dominant, and polygenic. Limited cross-resistance in WH-EB indicates that emamectin benzoate can be rotated with other classes of insecticides to which it does not show cross-resistance to delay the evolution of resistance in S. exigua. The incompletely dominant nature of resistance in S. exigua may explain the rapid evolution of resistance to emamectin benzoate in the field, and careful deployment of this chemical within a resistance management program should be considered.
Planthoppers in the genus Nilaparvata Distant are serious pests of rice and many other crops in tropical and temperate Asia, and northern Australia. In this study, the mitochondrial genomes of four Nilaparvata planthoppers were sequenced, three in Nilaparvata lugens Sta° l and one in Nilaparvata muiri China. Mitochondrial genome of Nilaparvata contain the standard set of 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and a control region. The nucleotide composition of Nilaparvata mitochondrial sequence is biased toward adenine and thymine, and the amino acid composition is affected to a similar degree by the bias to AT. We compare the four mitochondrial genomes and find intra- and interspecific variation in gene length, base composition, nucleotide and amino acid substitutions, intergenic spacer length, and gene overlap. The intra- and interspecific variations reveal that nucleotide and amino acid substitutions in mitochondrial protein-coding genes make a contribution to the formation of various insect biotypes in one species. Furthermore, the accumulation of nonsynonymous substitutions in the mitochondrial protein-coding genes, as well as differences in start codons, the length of intergenic spacers, and gene overlap regions contribute to differences between the two species investigated here. In addition, cox is the most conserved gene family and nad4-nad4l cluster is variable in Nilaparvata mitochondrial genes for the intra- and interspecific variation.
Recent research on the wheat curl mite species complex has revealed extensive genetic diversity that has distinguished several genetic lineages infesting bread wheat (Triticum aestivum L.) and other cereals worldwide. Turkey is the historical region of wheat and barley (Hordeum vulgare L.) domestication and diversification. The close relationship between these grasses and the wheat curl mite provoked the question of the genetic diversity of the wheat curl mite in this region. The scope of the study was to investigate genetic differentiation within the wheat curl mite species complex on grasses in Turkey. Twenty-one wheat curl mite populations from 16 grass species from nine genera (Agropyron sp., Aegilops sp., Bromus sp., Elymus sp., Eremopyrum sp., Hordeum sp., Poa sp., Secale sp., and Triticum sp.) were sampled in eastern and southeastern Turkey for genetic analyses. Two molecular markers were amplified: the cytochrome oxidase subunit I coding region of mtDNA (COI) and the D2 region of 28S rDNA. Phylogenetic analyses revealed high genetic variation of the wheat curl mite in Turkey, primarily on Bromus and Hordeum spp., and exceptionally high diversity of populations associated with bread wheat. Three wheat-infesting wheat curl mite lineages known to occur on other continents of the world, including North and South America, Australia and Europe, were found in Turkey, and at least two new genetic lineages were discovered. These regions of Turkey exhibit rich wheat curl mite diversity on native grass species. The possible implications for further studies on the wheat curl mite are discussed.
The regulation of mRNA expression level is critical for gene expression studies. Currently, quantitative reverse transcription polymerase chain reaction (qRT-PCR) is commonly used to investigate mRNA expression level of genes under various experimental conditions. An important factor that determines the optimal quantification of qRT-PCR data is the choice of the reference gene for normalization. To advance gene expression studies in Toxoptera citricida (Kirkaldy), an important citrus pest and a main vector of the Citrus tristeza virus, we used five tools (GeNorm, NormFinder, BestKeeper, ΔCt methods, and Ref Finder) to evaluate seven candidate reference genes (elongation factor-1 alpha [EF1α], beta tubulin [β-TUB], 18S ribosomal RNA [18S], RNA polymerase II large subunit (RNAP II), beta actin (β-ACT), alpha tubulin, and glyceraldhyde-3-phosphate dehydrogenase) under different biotic (developmental stages and wing dimorphism) and abiotic stress (thermal, starvation, and UV irradiation) conditions. The results showed that EF1α and 18S were the most stable genes under various biotic states, β-ACT and β-TUB during thermal stress, EF1α and RNAP II under starvation stress, and RNAP II, β-ACT, and EF1α under UV irradiation stress conditions. This study provides useful resources for the transcriptional profiling of genes in T. citricida and closely related aphid species.
Cotton fleahopper (Pseudatomoscelis seriatus Reuter) (Hemiptera: Miridae) is a piercing—sucking insect that has emerged as a major pest of cotton (Gossypium hirsutum L.) in Texas. Cotton fleahoppers feed on floral buds, commonly referred to as squares, causing damage and abscission, and subsequent yield loss. Previous studies indicate that plant resistance to cotton fleahopper is present in upland cotton, but the mechanism of resistance remains undetermined. In this study, Pilose, a cultigen of G. hirsutum, was examined as a source of resistance to cotton fleahopper, focusing on mechanism of resistance and heritability of the resistance trait. Results indicated that the resistance trait in Pilose is heritable and that pubescence is causative of resistance or that the resistance trait may be tightly linked to genes controlling pubescence. Behavioral assays indicated nonpreference as a mode of resistance in plants with dense pubescence.
The western chinch bug, Blissus occiduus Barber, is a serious pest of buffalograss, Buchloe dactyloides (Nuttall) due to physical and chemical damage caused during the feeding process. Although previous work has investigated the feeding behaviors of chinch bugs in the Blissus complex, no study to date has explored salivary gland morphology and the associated salivary complex of this insect. Whole and sectioned B. occiduus salivary glands were visualized using light and scanning electron microscopy to determine overall structure and cell types of the salivary glands and their individual lobes. Microscopy revealed a pair of trilobed principal glands and a pair of tubular accessory glands of differing cellular types. To link structure with function, the salivary gland proteome was characterized using liquid chromatography tandem mass spectrometry. The salivary proteome analysis resulted in B. occiduus sequences matching 228 nonhomologous protein sequences of the pea aphid, Acyrthosiphon pisum (Harris), with many specific to the proteins present in the salivary proteome of A. pisum. A number of sequences were assigned the molecular function of hydrolase and oxido-reductase activity, with one specific protein sequence revealing a peroxidase-like function. This is the first study to characterize the salivary proteome of B. occiduus and the first of any species in the family Blissidae.
In field tests conducted in south Florida to test grape juice as a bait for the Caribbean fruit fly, Anastrepha suspensa Loew, high numbers of Zaprionus indianus Gupta were captured in traps with aqueous grape juice. These experiments included comparisons of grape juice bait with established A. suspensa protein-based baits (ammonium acetate putrescine lures, or torula yeast) or wine, a bait found previously to be attractive to Z. indianus. Effects of different preservatives (polypropylene glycol, polyethylene glycol, proxel, or sodium tetraborate) and bait age were also tested. Traps with grape juice baits captured more A. suspensa than unbaited traps, but more were captured in traps with grape juice plus preservative baits and the highest numbers were captured in traps containing the established protein-based baits. In contrast, grape juice baits without preservative that were prepared on the day of deployment (0 d) or that were aged for 3–4 d in the laboratory captured the highest numbers of Z. indianus, while solutions that were aged in the laboratory for 6 or 9 d captured fewer. Although these studies found that aqueous grape juice is a poor bait for A. suspensa, we found that actively fermenting aqueous grape juice may be an effective bait for Z. indianus.
Oligonychus perseae Tuttle, Baker, & Abatiello is a foliar pest of ‘Hass’ avocados [Persea americana Miller (Lauraceae)]. The recommended action threshold is 50–100 motile mites per leaf, but this count range and other ecological factors associated with O. perseae infestations limit the application of enumerative sampling plans in the field. Consequently, a comprehensive modeling approach was implemented to compare the practical application of various binomial sampling models for decision-making of O. perseae in California. An initial set of sequential binomial sampling models were developed using three mean—proportion modeling techniques (i.e., Taylor's power law, maximum likelihood, and an empirical model) in combination with two-leaf infestation tally thresholds of either one or two mites. Model performance was evaluated using a robust mite count database consisting of >20,000 Hass avocado leaves infested with varying densities of O. perseae and collected from multiple locations. Operating characteristic and average sample number results for sequential binomial models were used as the basis to develop and validate a standardized fixed-size binomial sampling model with guidelines on sample tree and leaf selection within blocks of avocado trees. This final validated model requires a leaf sampling cost of 30 leaves and takes into account the spatial dynamics of O. perseae to make reliable mite density classifications for a 50-mite action threshold. Recommendations for implementing this fixed-size binomial sampling plan to assess densities of O. perseae in commercial California avocado orchards are discussed.
In this study, the residual efficacy of spinetoram on concrete and galvanized steel surfaces was evaluated under fixed laboratory conditions against the rice weevil, Sitophilus oryzae (L.), the confused flour beetle, Tribolium confusum Jacquelin du Val, and the sawtoothed grain beetle, Oryzaephilus surinamensis (L.). Spinetoram was applied at the dose rates of 0.025 and 0.1 mg (active ingredient)/cm2, on steel surfaces that were stored in continuous darkness and on concrete surfaces that were stored either in continuous darkness or in 12:12 (L:D) photoperiod. The experimental period for the residual effect of spinetoram was 6 mo. Bioassays were conducted for all types of surfaces and storage conditions at monthly intervals starting from the initial application period (seven bioassays in total). For each bioassay, mortality of the exposed adult beetles was measured after 3 and 7 d of exposure. Among the tested species, T. confusum was the least susceptible, regardless of the surface type, storage conditions, and dose rate. Regarding the bioassays conducted in the surfaces stored in darkness, spinetoram proved very persistent and no reduction in the efficacy was noted throughout the experimental period. Moreover, there were no differences in spinetoram efficacy between the two types of surfaces. Conversely, in light [12:12 (L:D)] conditions spinetoram efficacy was notably reduced after the first month, but remained stable for the rest of the period. The results of this study indicate that spinetoram was persistent with long residual efficacy against major stored grain beetle species on the most common types of surfaces in continuous darkness, while the presence of light reduced its efficacy.
Larval competition is particularly prevalent among grain beetles that remain within their mother-selected grain throughout development, and the behavioral process of competition is usually inferred by the competition outcome. The Mexican bean weevil Zabrotes subfasciatus (Boheman) is subjected to resource availability variation because of the diversity of common bean types and sizes, from small (e.g., kidney beans) to large (e.g., cranberry beans). The competition process was identified in the Mexican bean weevil reared on kidney and cranberry beans by inference from the competition outcome and by direct observation through digital X-ray imaging. Increased larval density negatively affected adult emergence in kidney beans and reduced adult body mass in both kidney and cranberry beans. Developmental time was faster in cranberry beans. The results allowed for increased larval fitness (i.e., higher larval biomass produced per grain), with larval density reaching a maximum plateau >5 hatched larvae per kidney bean, whereas in cranberry beans, larval fitness linearly increased with density to 13 hatched larvae per bean. These results, together with X-ray imaging without evidence of direct aggressive interaction among larvae, indicate scramble competition, with multiple larvae emerging per grain. However, higher reproductive output was detected for adults from lower density competition with better performance on cranberry beans. Larger populations and fitter adults are expected in intermediate larval densities primarily in cranberry beans where grain losses should be greater.
This study aimed to identify and quantify the compounds present in the abdominal glands of Alphitobius diaperinus Panzer, 1797 (Coleoptera: Tenebrionidae) and to evaluate the influence of these compounds on its behavior. The extraction of volatiles present in the abdominal glands was made by dissection (10 individuals per sex) and by air entrainment (200 insects per sex), and they were analyzed by gas chromatography—flame ionization detector, gas chromatograph—mass spectrometer, and gas chromatograph—electroantennography detector (GC-EAD). The influence of these volatiles on the behavior of conspecifics was evaluated in a four-arm olfactometer. Twenty-three compounds were identified from male and female abdominal gland extracts, of which six were quinones: the 2-methyl-1,4-benzoquinone and the 2-ethyl-1,4-benzoquinone were the major components, and 1,4 benzoquinone and three hydroquinones were registered for the first time for this species. The GC-EAD analysis using the crude extracts from abdominal glands showed that male and female antennae responded to the three major benzoquinones. For the olfactometer bioassays, both genders were repelled either by the abdominal gland extracts or by synthetic solutions containing the three benzoquinones. The results suggest that the 1,4-benzoquinones play a role as a repellent to A. diaperinus.
Pheromone-lured funnel traps are widely used for pest monitoring and mass trapping in agricultural fields and stores. DDVP vapona (dichlorvos), the insecticide of choice as a killing agent inside traps, has been banned, and research on new products is being pursued. Essential oils (EO) could be an alternative if properly formulated. To test their potential, beads of encapsulated coriander and basil EO were tested in funnel traps in stores of almonds and pet foods during 2 mo. The number of adult moth (Plodia interpunctella (Hübner) and Ephestia kuehniella Zeller) dead captures was similar with either coriander or basil EO beads and with vapona tablets while there were more insects alive in the control. These preliminary results indicate a good potential for the development of such natural products as an alternative to synthetic insecticides to include them inside funnel traps.
Sodium fluoride (NaF) is a wood preservative with fungicidal activity and antifeedant activity against termites. In this study, wood blocks of Pinus massoniana were treated with a 0.5% (wt/wt) aqueous solution of NaF, and placed in soil contact under field conditions to evaluate leachability of NaF and resistance to Reticulitermes flaviceps (Oshima). Fluoride leachate levels in soil from wood-soil locations were also determined. After 12-mo outdoor exposure, 91.54% of fluoride was leached from NaF-treated wood and fluoride retention of the wood was 154.28 µg/g wood. In NaF-treated wood-soil locations, soil fluoride residues were significantly higher than locations with the water-treated negative control. Termite activity (presence or occupation) on NaF-treated blocks was 6.25% which was significantly less than 40.00% activity on water-treated control blocks. The mass lost from the wood of NaF-treated blocks was 17.46% which was significantly less than the 45.21% loss from the water-treated blocks. The results show that fluoride is readily leachable from treated wood into surrounding soil. NaF treatment can reduce termite damage to wood under field conditions, and this compound should receive further consideration as a wood preservative to protect timber from termite damage.
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