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During the past two decades, onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), has become a global pest of increasing concern in commercial onion (Allium cepa L.), because of its development of resistance to insecticides, ability to transmit plant pathogens, and frequency of producing more generations at high temperatures. T. tabaci feeds directly on leaves, causing blotches and premature senescence as well as distorted and undersized bulbs. T. tabaci can cause yield loss >50% but can be even more problematic when it transmits Iris yellow spot virus (family Bunyaviridae, genus Tospovirus, IYSV). IYSV was identified in 1981 in Brazil and has spread to many important onion-producing regions of the world, including several U.S. states. IYSV symptoms include straw-colored, dry, tan, spindle- or diamond-shaped lesions on the leaves and scapes of onion plants and can cause yield loss up to 100%. Here, we review the biology and ecology of T. tabaci and discuss current management strategies based on chemical, biological, and cultural control as well as host resistance. Future directions for research in integrated pest management are examined and discussed.
The pecan weevil, Curculio caryae (Horn), is a key pest of pecan [Carya illinoinensis (Wangenh.) K. Koch], Current control recommendations are based on chemical insecticide applications. Microbial control agents such as the entomopathogenic nematode, Steinernema carpocapsae (Weiser) and the fungus Beauveria bassiana (Balsamo) Vuillemin occur naturally in southeastern U.S. pecan orchards and have shown promise as alternative control agents for C. caryae. Conceivably, the chemical and microbial agents occur simultaneously within pecan orchards or might be applied concurrently. The objective of this study was to determine the interactions between two chemical insecticides that are used in commercial C. caryae control (i.e., carbaryl and cypermethrin applied below field rates) and the microbial agents B. bassiana and S. carpocapsae. In laboratory experiments, pecan weevil larval or adult mortality was assessed after application of microbial or chemical treatments applied singly or in combination (microbial chemical agent). The nature of interactions (antagonism, additivity, or synergy) in terms of weevil mortality was evaluated over 9 d (larvae) or 5 d (adults). Results for B. bassiana indicated synergistic activity with carbaryl and antagonism with cypermethrin in C. caryae larvae and adults. For S. carpocapsae, synergy was detected with both chemicals in C. caryae larvae, but only additive effects were detected in adult weevils. Our results indicate that the chemical-microbial combinations tested are compatible with the exception of B. bassiana and cypermethrin. In addition, combinations that exhibited synergistic interactions may provide enhanced C. caryae control in commercial field applications; thus, their potential merits further exploration.
Bactrocera invadens Drew, Tsuruta & White (Diptera: Tephritidae) is spreading throughout central Africa attacking a variety of fruit; quarantines are placed on fruit from this region that are considered hosts. The only phytosanitary treatment that is commercially available is an ionizing irradiation treatment for all Tephritidae at 150 Gy. The development of other treatments, such as heat, cold, or fumigation, usually requires testing tens of thousands of insects at a dose that provides efficacy and may take several years. It may be possible to shorten the time required to develop treatments by comparing tolerance of a new quarantine pest to tolerances of pests with similar behaviors and modes of infestation for which treatment schedules are available. Cold and heat tolerance of B. invadens was compared with tolerance of Anastrepha ludens (Loew), Bactrocera dorsalis (Hendel), and Ceratitis capitata (Wiedemann) in vitro. Third-instar B. invadens was no more cold tolerant than the other species when treated in diet at 0.94 ± 0.65°C and no more heat tolerant than C. capitata when immersed in vials in water at 44.7 ± 0.1°C. The data at 0.94 ± 0.65°C was used to include B. invadens in a USDA cold treatment schedule for citrus fruit from Africa so that trade would not be interrupted while protecting U.S. agriculture from this invasive pest.
Olfactory cues released by adult bees, brood, pollen, and honey from a honey bee, Apis mellifera L., colony are the primary stimuli that guide the beetle Aethina tumida Murray (Coleoptera: Nitidulidae) to host colonies. To investigate the response of adult A. tumida to visual stimuli, we tested the influence of color and height on trap efficiency. Two pole trap colors (black and white) were evaluated at three heights (46 cm, 1 m, and 3 m) from October 2008 to December 2009. A. tumida were trapped in the greatest numbers between 17 April and 15 May 2009. The lowest numbers were captured during the winter and fall. The trapping results showed that both color and trap height significantly influenced capture. The average catch in the white traps (mean ± SE, 2.47 ± 0.30) was significantly higher than that of the black traps (1.53 ± 0.29) probably because white is more reflective than black. Among the heights evaluated, there were more beetles caught when traps were positioned at 46 cm (the same height as the entrance of the hives) with 3.07 ± 0.51 beetles compared with beetles captured at 1 m (1.88 ± 0.30) or 3 m (1.06 ± 0.18) high. Male and female beetles exhibited similar responses to trap color and height. The relationship between the numbers of beetles in colonies and capture rates in traps was very poor and did not provide a basis to evaluate trap efficiency. In addition, because capture rates seemed generally low in relationship to the number of beetles in the apiary, substantial improvements to the trap may be necessary.
Leaf-cutting ants in the genus Atta F. (Formicidae, Attini) are among the most important pest arthropods in Central and South America, consuming more vegetation than any other animal group. Among the organisms attacking ants in nature, flies of the family Phoridae have been proposed as the most promising biocontrol agents for pest ants. Four phorid species, Apocephalus setitarsus Brown, Myrmosicarius brandaoi Disney, Myrmosicarius gonzalezae Disney, and Eibesfeldtphora trilobata Disney, were reared from ants collected at Atta vollenweideri Forel nests and off foraging trails in Santa Fe province in Argentina. E. trilobata attacked larger ants and had bigger adults than the other species, also exhibiting the longest developmental time. Correlations between size of hosts and size of adults, as well as between size of adults and developmental times, could be established only in some cases. No differences were found between the sizes of the hosts from which males and females emerged. The natural percentage of parasitism varied throughout the seasons and seemed to be influenced by the extreme drought affecting the study site. We discuss why all four species would be suitable candidates for integrating an assemblage of biocontrol agents against A. vollenweideri.
Bacillus thuringiensis subspecies kurstaki and aizawai are important control agents for lepidopteran pests. Bioassays were designed to test B. t. kurstaki and aizawai against second- and-fourth instar black cutworm larvae with and without Bacillus sp. NFD2 and Pseudomonas sp. FNFD1 bacteria. B. thuringiensis subsp. aizawai (XenTari) was more toxic to both second- and fourth-instar black cutworm, Agrolis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), larvae than B. t. kurstaki (DiPel) at 7 d after treatment (DAT). When DiPel was combined with NFD2 or FNFD1 versus second instars, the LC50s were 5.0× and 4.7× lower, respectively, than with DiPel alone. DiPel combined with both NFD2 and FNFD1 versus second instars resulted in an LC50 value 7.7× lower than with DiPel alone. When XenTari was combined with NFD2 or FNFD1 versus second instars, the LC50s were 5.2× and 3.8× lower, respectively, than with XenTari alone. XenTari combined with both NFD2 and FNFD1 versus second instars resulted in an LC50 9.7× lower than with XenTari alone. When DiPel was combined with NFD2 or FNFD1 versus fourth instars, the LC50s were 4.4× and 3.4× lower, respectively, than with DiPel alone. DiPel combined with both NFD2 and FNFD1 versus fourth instars resulted in an LC50 5.0× lower than with DiPel alone. When XenTari was combined with NFD2 or FNFD1 versus fourth instars, the LC50s were 5.7× and 3.3× lower, respectively, than with XenTari alone. XenTari combined with both NFD2 and FNFD1 versus fourth instars resulted in an LC50 6.7× lower than with XenTari alone.
The lesser peachtree borer, Synanthedon pictipes (Grote & Robinson) (Lepidoptera: Sesiidae), is indigenous to eastern North America. It is a pest of commercially grown Prunus spp., especially to southeastern peach orchards where earlier regulatory changes affected pesticide use on peach leading to increased S. pictipes damage. Pest management practices are now having a positive effect toward control of this pest, but cost-competitive biological control solutions that promote environmental stewardship are needed. Here, we tested four Steinernema species and five Heterorhabditis species of entomopathogenic nematodes against larval S. pictipes. Included were four strains of S. carpocapsae (All, DD136, Sal, and Hybrid2) and three strains of S. riobrave (3–8b, 7–12, and 355). Larvae treated with any strain of S. carpocapsae always resulted in <20% survival, whereas larval survival was always >50% when treated with any other Steinernema or Heterorhabditis spp. These differences were always significant for the Hybrid2 strain of S. carpocapsae and similarly for other tested S. carpocapsae strains except for when larvae were treated with the 3–8b strain of S. riobrave. In addition, we determined the susceptibility of different size S. pictipes larvae, because they occur simultaneously in orchards, and we found that larvae rated as “medium” and “large” were significantly more susceptible than “small” larvae. Last, we demonstrated that moisture-retaining covers (placed over S. pictipes-infested wounds on peach limbs) increased efficacy of nematode treatments against larval S. pictipes. Even when using highly virulent nematodes against S. pictipes, it is likely that an aboveground application will require an environmental modification to remain efficacious.
The most common hosts for the West Indian fruit fly, Anastrepha obliqua (Macquart) (Diptera: Tephritidae) are fruit in the family Anacardiaceae (mango [Mangifera L.] and mombin [Spondias L.] species). However, similar to many of the tropical fruit flies of major economic importance, this species attacks several other families of crop fruit, including Annonaceae (cherimoya, Annona cherimola Mill.), Myrtaceae (guava, Psidium L.), Oxalidaceae (carambola, Averrhoa carambola L.), Passifloraceae (granadilla, Passiflora quadrangularis Mill.), and Sapotaceae [mamey sapote, Pouteria sapota (Jacq.) H. E. Moore & Stearn]. In the family Rutaceae the economically important genus Citrus has been reported and until recently considered a host for this fruit fly. In this study, we reviewed the taxonomy of A. obliqua, tested specific chemicals that may inhibit oviposition, compared egg-to-adult survival of A. obliqua on preferred hosts and on grapefruit (Citrus × paradisi Macfad.), and measured fruit tissue-specific developmental rates of A. obliqua and the known citrus breeding Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae), from egg to pupae. Our literature review shows much confusion concerning the taxonomy of this and related Anastrepha species, including synonymies and confusion with other species. The deterrent effect of the highest concentration of flavonoids for oviposition, although significant, was not absolute. Experiments carried out under laboratory conditions showed 15–40 times greater survival of A. ludens (whose preferred hosts include Rutaceae) on grapefruit compared with A. obliqua for both tree attached and harvested fruit. Experiments of survival of developing stages over time showed that the two species oviposit into different tissues in the fruit, and mortality is much higher for the West Indian fruit fly in the flavedo and albedo of the fruit compared with the Mexican fruit fly.
Methyl bromide fumigation is widely used as a phytosanitary treatment. Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae), is a quarantine pest of several fruit, including citrus (Citrus spp.), exported from Texas, Mexico, and Central America. Recently, live larvae have been found with supposedly correctly fumigated citrus fruit. This research investigates the efficacy of the previously approved U.S. Department of Agriculture—Animal and Plant Health Inspection Service treatment schedule: 40 g/m3 methyl bromide at 21–29.4°C for 2 h. Tolerance of A. ludens to methyl bromide in descending order when fumigated in grapefruit (Citrus × paradisi Macfad.) is third instar > second instar > first instar > egg. Two infestation techniques were compared: insertion into fruit of third instars reared in diet and oviposition by adult A. ludens into fruit and development to the third instar. Inserted larvae were statistically more likely to survive fumigation than oviposited larvae. When fruit were held at ambient temperature, 0.23 ± 0.12% of larvae were still observed to be moving 4 d postfumigation. Temperatures between 21.9 and 27.2°C were positively related to efficacy measured as larvae moving 24 h after fumigation, pupariation, and adult emergence. Coating grapefruit with Pearl Lustr 2–3 h before fumigation did not significantly affect the proportion of third instars moving 24 h after fumigation, pupariating, or emerging as adults. In conclusion, fumigation with 40 g/m3 methyl bromide for 2 h at fruit temperatures >26.7°C is not found to be inefficacious for A. ludens. Although a few larvae may be found moving >24 h postfumigation, they do not pupariate.
Ash (Fraxinus spp.) logs, infested with fully developed, cold-acclimated larval and prepupal emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), were fumigated with methyl bromide (MeBr) at 4.4 and 10.0°C for 24 h. Concentrations × time dosages of MeBr obtained were 1,579 and 1,273 g-h/m3 (24-h exposure) at 4.4 and 10.0°C after applied doses of 112 and 96 g/m3, respectively. MeBr concentrations were simultaneously measured with a ContainIR infrared monitor and Fumiscope thermal conductivity meter calibrated for MeBr to measure the effect of CO2 on Fumiscope concentration readings compared with the infrared (IR) instrument. The presence of CO2 caused false high MeBr readings. With the thermal conductivity meter, CO2 measured 11.36 g/m3 MeBr per 1% CO2 in clean air, whereas the gas-specific infrared ContainIR instrument measured 9.55% CO2 as 4.2 g/m3 MeBr (0.44 g/m3 per 1% CO2). The IR instrument was 0.4% as sensitive to CO2 as the thermal conductivity meter. After aeration, fumigated and control logs were held for 8 wk to capture emerging beetles. No A. planipennis adults emerged from any of the fumigated logs, whereas 262 emerged from control logs (139 and 123/m2 at 4.4 and 10.0°C, respectively). An effective fumigation dose and minimum periodic MeBr concentrations are proposed. The use of a CO2 scrubber in conjunction with nonspecific thermal conductivity instruments is necessary to more accurately measure MeBr concentrations.
Metabolic stress disinfection and disinfestation (MSDD) is a postharvest treatment designed to control pathogens and arthropod pests on commodities that combines short cycles of low pressure/vacuum and high CO2 with ethanol vapor. Experiments were conducted to evaluate the effect of MSDD treatment on various life stages of Ceratitis capitata (Wiedemann), Mediterranean fruit fly; Bactrocera dorsalis Hendel, oriental fruit fly; and Bactrocera Cucurbitae Coquillett, melon fly, in petri dishes and in papaya, Carica papaya L., fruit. In some experiments, the ethanol vapor phase was withheld to separate the effects of the physical (low pressure/ambient pressure cycles) and chemical (ethanol vapor plus low pressure) phases of treatment. In the experiments with tephritid fruit fly larvae and adults in petri dishes, mortality was generally high when insects were exposed to ethanol and low when ethanol was withheld during MSDD treatment, suggesting that ethanol vapor is highly lethal but that fruit flies are quite tolerant of short periods of low pressure treatment alone. When papaya fruit infested with fruit fly eggs or larvae were treated by MSDD, they produced fewer pupae than untreated control fruit, but a substantial number of individuals developed nonetheless. This suggests that internally feeding insects in fruit may be partially protected from the toxic effects of the ethanol because the vapor does not easily penetrate the fruit pericarp and pulp. MSDD treatment using the atmospheric conditions tested has limited potential as a disinfestation treatment for internal-feeding quarantine pests such as fruit flies infesting perishable commodities.
The biological control agent Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) is a gregarious larval endoparasitoid of the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), an invasive cambium-feeding species responsible for recent, widespread mortality of ash (Fraxinus spp.) in North America. T. planipennisi is known to prefer late-instar emerald ash borer, but the cues used to assess host size by this species and most other parasitoids of concealed hosts remain unknown. We sought to test whether vibrations produced by feeding emerald ash borer vary with larval size and whether there are any correlations between these cues and T. planipennisi progeny number (i.e., brood size) and sex ratio. The amplitudes and rates of 3–30-ms vibrational impulses produced by emerald ash borer larvae of various sizes were measured in the laboratory before presenting the larvae to T. planipennisi. Impulse-rate did not vary with emerald ash borer size, but vibration amplitude was significantly higher for large larvae than for small larvae. T. planipennisi produced a significantly higher proportion of female offspring from large hosts than small hosts and was shown in previous work to produce more offspring overall from large hosts. There were no significant correlations, however, between the T. planipennisi progeny data and the emerald ash borer sound data. Because vibration amplitude varied significantly with host size, however, we are unable to entirely reject the hypothesis that T. planipennisi and possibly other parasitoids of concealed hosts use vibrational cues to assess host quality, particularly given the low explanatory potential of other external cues. Internal chemical cues also may be important.
Three experiments were conducted to determine the influence of number of coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae: Scolytinae), females (one, two, or five) reared in artificial diet on fecundity and subsequent development of larvae, pupae, and adults. Our results demonstrated that increasing female density from one to two or five individuals did not result in the expected two- or five-fold increase in progeny, despite ample food resources available. Instead, decreased fecundity was observed with increasing density for all experiments. The mechanism reducing fecundity was not identified, but possibly, volatiles are being produced (e.g., host-marking pheromones). The decrease in fecundity may explain why infestations of only one colonizing female per berry are the norm in the field.
The lacewing Chrysoperla sinica (Tjeder) (Neuroptera: Chrysopidae) is an important predator of several insect pests in China and has considerable potential as a biological control agent. An inoculative approach would be the releasing adults early in the season to ensure that populations are present before pest densities increase. However, an understanding of adult flight activity under different conditions is necessary to develop appropriate release strategies. Therefore, we used a 32-channel, computer-monitored flight mill system to determine the effect of age on the flight activity of unmated female and male adults. Both sexes had high total flight activity levels as well as the longest individual flight bouts 2 and 3 d after emergence. The effects of temperature (between 13 and 33°C at 75% RH) and relative humidity (between 30 and 90% RH at 23°C) on the flight activity of 3-d-old unmated adults also were determined. Flight activity declined at the lowest (13°C) and highest (33°C) temperatures tested, as well as at the lowest relative humidity (30% RH). These findings are discussed within the context of selecting the appropriate environmental conditions for releasing C. sinica.
Organophosphorus (OP) insecticides are widely used in agriculture, which are toxic to insect pests and nontarget organisms. The current study mainly assessed the effect of the pesticide phoxim on oxidative stress by certain biomarkers in the fat body and midgut of the silkworm, Bombyx mori (L.), after exposure to 50% lethal concentration (LC50) of phoxim for 2 h. Malondialdehyde (MDA) content, activity of glutathione transferase (GST), and expression of GST at transcriptional level were assayed. LC50 value of phoxim was 2.5 mg/liter at 2-h exposure for the day 3 of the fifth-instar larvae. After exposure of phoxim, MDA content in the fat body significantly increased at 4–20 h posttreatment (p.t.), the highest increase was ≈4.11-fold from 0.451 ± 0.053 to 1.854 ± 0.113 nmol/mg protein compared with corresponding control. In the midgut, significant increase in the MDA content (from 1.40- to 3.16-fold) was observed at 8–42 h p.t. The activity of GSTs increased to 1.48–2.00-fold at 24–42 h p.t. and 1.33–1.48-fold at 20–24 h p.t. in the fat body and midgut, respectively. The peroxidase activity of GSTs also was induced, which increased to 1.46–2.06-fold and 1.31–1.50-fold in the fat body and midgut, respectively. BmGSTe8 showed a late up-regulation of transcripts at 24–42 h after exposure to phoxim, which might contribute to the improved phoxim tolerance of silkworm larvae. These results indicated that phoxim could trigger oxidative stress and that MDA content and GST activity might be used as biomarkers of OP insecticide exposure. In addition, activity of GSTs were more inducible in the fat body than in midgut.
Evidence for pollinator declines has led to concern that inadequate pollination services may limit crop yields. The global trade in commercial bumble bee (Bombus spp.) colonies provides pollination services for both glasshouse and open-field crops. For example, in the United Kingdom, commercial colonies of nonnative subspecies of the bumble bee Bombus terrestris L. imported from mainland Europe are widely used for the pollination of raspberries, Rubus idaeus L. The extent to which these commercial colonies supplement the services provided by wild pollinators has not been formally quantified and the impact of commercial bumble bees on native bees visiting the crop is unknown. Here, the impacts of allowing commercially available bumble bee colonies to forage on raspberry canes are assessed in terms of the yield of marketable fruit produced and the pollinator communities found foraging on raspberry flowers. No differences were found in the abundance, diversity, or composition of social bee species observed visiting raspberry flowers when commercial bumble bees were deployed compared with when they were absent. However, weight of marketable raspberries produced increased when commercial bees were present, indicating that wild pollinator services alone are inadequate for attaining maximum yields. The findings of the study suggests that proportional yield increases associated with deployment of commercial colonies may be small, but that nevertheless, investment in commercial colonies for raspberry pollination could produce very significant increases in net profit for the grower. Given potential environmental risks associated with the importation of nonnative bumble bees, the development of alternative solutions to the pollination deficit in raspberry crops in the United Kingdom may be beneficial.
Methyl salicylate, an herbivore-induced plant volatile, has been shown to attract natural enemies and affect herbivore behavior. In this study, methyl salicylate was examined for its attractiveness to natural enemies of the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), and for its direct effects on soybean aphid population growth rates. Methyl salicylate lures were deployed in plots within organic soybean [Glycine max (L.) Merr.] fields. Sticky card traps adjacent to and 1.5 m from the lure measured the relative abundance of natural enemies, and soybean aphid populations were monitored within treated and untreated plots. In addition, exclusion cage studies were conducted to determine methyl salicylate's effect on soybean aphid population growth rates in the absence of natural enemies. Significantly greater numbers of syrphid flies (Diptera: Syrphidae) and green lacewings (Neuroptera: Chrysopidae) were caught on traps adjacent to the methyl salicylate lure, but no differences in abundance were found at traps 1.5 m from the lure. Furthermore, abundance of soybean aphids was significantly lower in methyl salicylate-treated plots. In exclusion cage studies, soybean aphid numbers were significantly reduced on treated soybean plants when all plants were open to natural enemies. When plants were caged, however, soybean aphid numbers and population growth rates did not differ between treated and untreated plants suggesting no effect of methyl salicylate on soybean aphid reproduction and implicating the role of natural enemies in depressing aphid populations. Although aphid populations were reduced locally around methyl salicylate lures, larger scale studies are needed to assess the technology at the whole-field scale.
Laboratory and field studies were undertaken to determine the effects of increased numbers of trichomes on seedling stems, petioles, and first true leaves of Brassica napus L., canola, on the feeding and behavior of the crucifer flea beetle Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae). Seedlings of ‘Westar’ canola with genes inserted from Arabidopsis thaliana L. for increased trichome production, called Hairy1, were tested against Westar seedlings in no-choice and choice laboratory tests, and against parental plants and other cultivars grown from seed with and without insecticide in field trials at Saskatoon and Lethbridge, Canada. Analyses of prefeeding and feeding behavior in no-choice tests of first true leaves found that flea beetles interacted with their host while off Hairy1 leaves more so than beetles presented with leaves of Westar. Beetles required twice as much time to reach satiation when feeding on leaves with increased pubescence than on Westar leaves. In laboratory choice tests, flea beetles fed more on cotyledons and second true leaves of Westar than on comparable tissues of the transgenic line. In field trials, variations in feeding patterns were seen over time on cotyledons of the line with elevated trichomes. However, all four young true leaves of Hairy1 seedlings were fed upon less than were the parental lines. Feeding on Hairy1 plants frequently occurred at levels equal to or less than on cultivars grown from insecticide-treated seed. This study highlights the first host plant resistance trait developed in canola, dense pubescence, with a strong potential to deter feeding by crucifer flea beetles.
Brown stink bug, Euschistus servus (Say), and green stink bug, Acrosternum hilare (Say) (Hemiptera: Pentatomidae), are major agricultural pests. Although various insecticides are used to control nymphs and adults, little is known about how they affect eggs. Laboratory bioassays and field trials were conducted to determine the efficacy of common field rates of acephate, λ-cyhalothrin, spinosad, and thiamethoxam on developing E. servus and A. hilare eggs, as well as Telenomus podisi Ashmead (Hymenoptera: Scelionidae) parasitoids developing in E. servus eggs. In laboratory bioassays, egg masses were dipped into insecticide and water solutions and assessed for mortality after 2 wk. In the field trials, egg masses on a cloth section were pinned to leaves in each plot of a randomized complete block and returned to the laboratory 24 h after exposure to insecticide sprays. Mortality was assessed after 2 wk. In dip bioassays, there was a significant effect of insecticide treatment on A. hilare eggs with all insecticides resulting in greater mortality than the water control. However, no effect of treatment occurred in the field with A. hilare or for E. servus eggs in both the laboratory bioassays and the field trials. In contrast, developing T. podisi parasitoids showed significant mortality when exposed to all insecticide treatments, when dipped or field-treated. Spinosad and λ-cyhalothrin treatments resulted in 100% mortality of T.podisi, and acephate resulted in greater mortality than thiamethoxam. Our results suggest that there is relatively little efficacy from insecticide sprays on stink bugs developing in eggs but that mortality of egg parasitoids may be significant.
The feeding of soil dwelling insects on storage roots is one of the most serious management issues faced by sweetpotato, Ipomoea batatas (L.) Lam. (Convolvulaceae), growers in the southern United States. Field studies were conducted to evaluate the relative susceptibility of two commonly grown sweetpotato varieties to sweetpotato flea beetle, Chaetocnema confinis Crotch (Coleoptera: Chrysomelidae), and wireworms (Coleoptera: Elateridae, various species). The incidence and severity of sweetpotato flea beetle damage was significantly lower in the variety Covington than Beauregard in two small plot replicated studies. Surveys conducted in commercial sweetpotato fields also showed significantly less sweetpotato flea beetle damage in fields planted to Covington compared with those planted to Beauregard. There was no clear evidence of varietal effect on the incidence of wireworm damage in the study. Results indicate that the severity of wireworm damage as measured by the size of feeding scars may be less in Covington than Beauregard.
Jatropha curcas L. (Euphorbiaceae) is being increasingly planted worldwide, but questions remain regarding its pollination biology. This study examined the contribution of diurnal and nocturnal insects to the pollination of monoecious J. curcas, through its floral biology, pollination ecology, and foraging behavior of potential pollinators. Nectar production of both male and female flowers peaked in the morning, declined in the afternoon, and rapidly bottomed during the night in all of their anthesis days. The diurnal visitors to the flowers of J. curcas are bees and flies, and the nocturnal visitors are moths. Flowers received significantly more visits by diurnal insects than by nocturnal insects. Through bagging flowers during night or day or both or exclusion, we compared fruit and seed production caused by diurnal and nocturnal pollinators. Both nocturnal and diurnal visitors were successful pollinators. However, flowers exposed only to nocturnal visitors produced less fruits than those exposed only to diurnal visitors. Thus, diurnal pollinators contribute more to seed production by J. curcas at the study site.
Lesser cornstalk borer, Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae) is an important pest of sugarcane (a complex hybrid of Saccharum spp.) in southern Florida. Cultural controls for E. lignosellus were evaluated in preparation for the potential loss of effective insecticides. Field studies conducted in 2006 compared the effects of harvest residues from green-harvested sugarcane (no preharvest burning to remove leaf matter) on E. lignosellus stalk damage and yield. Damage by E. lignosellus was significantly lower in plant cane plots that were covered with harvest residues collected from a green-harvested field before shoot emergence compared with plots without harvest residue. There were no yield differences between plots with and without harvest residues in plant or ratoon sugarcane fields in the 2006 study. The effects of three postharvest tillage levels (conventional, intermediate, and no tillage) were evaluated in preharvest burned and green-harvested fields in 2008 and 2009. Significantly less E. lignosellus damage was observed in the green- versus preharvest burned fields in both years. Intermediate and no-tillage plots had very little damage in green-harvested field. Conventional tillage plots had the greatest damage in the green-harvested field and the lowest damage in the preharvest burned field. In 2008, biomass yield was greater in the intermediate than conventional tillage in the green-harvested field, but it was greater in the conventional than in other tillage levels in the preharvest burned field. These studies demonstrated that cultural controls could greatly reduce E. lignosellus damage in sugarcane without the use of insecticides.
The density of colonies of leaf-cutting ants, Atta cephalotes L. (Hymenoptera: Formicidae), was measured and compared among coffee (Coffea arabica L.) plantations in five management categories: monoculture conventional, diversified conventional, diversified organic, highly diversified conventional, and highly diversified organic. Twenty-four small farms (<4 ha) in Turrialba, Costa Rica, were included in this study. Within-farm and off-farm (landscape) variables were measured and tested for their relationship with A. cephalotes colony density. Total ant colony density (colonies per ha) and density of new colonies shortly after a nuptial flight were significantly greater in the coffee monoculture conventional system, compared with all other systems. Total ant colony density and density of new colonies were inversely related to percentage of shade within the farms. Within farms, colony density was greater near edges adjacent to riparian forest than those adjacent to nonforested land. Regardless of edge type, plots closer to the edge (0–30 m) had greater colony density than those furthest from the edge. At the landscape scale, density of new colonies was positively related to fallow land use coverage within a 2,000-m buffer radius and to forest coverage within a 500-m radius. Results indicate that coffee farm management practices and landscape level factors can affect A. cephalotes colony densities. Understanding such practices and factors could assist in the development of better management methods of these injurious insects in coffee farms. Increased diversification in coffee farms, possibly due to the greater shade associated with it, may reduce colonization by the ants, which are considered forest gap specialists.
We conducted trapping experiments for the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) in Michigan, USA, and Ontario, Canada, to compare unbaited light green sticky prism traps with traps baited with phoebe oil, (Z)-3-hexenol (Z3-6:OH), or blends of other green leaf volatiles (GLVs) with Z3-6:OH. Traps were placed in the lower canopy of ash trees (Fraxinus spp.). Catches with Z3-6:OH—baited traps showed a significant male bias and these traps caught significantly more males than the unbaited controls at both sites. They were also superior to phoebe oil-baited traps and those baited with GLV blends. Catches with phoebe oil showed a significant female bias but there was no difference in the number of females captured between traps baited with phoebe oil or Z3-6:OH lures. Catches were analyzed at regular time intervals to examine the response of A. planipennis to the lures over the course of the flight season. Z3-6:OH—baited traps consistently caught more males than the controls at each interval throughout the flight season. Catches of females with Z3-6:OH and phoebe oil were significantly better than the controls early in the flight season but declined to control levels by midseason. Our results suggest that Z3-6:OH—baited green traps placed in the ash canopy would be a superior lure for detecting and monitoring A. planipennis throughout the flight season.
Although recent research has demonstrated that clays provide satisfactory control of some agricultural insect pests, the effect of clays on gall wasps that damage forest trees has not been previously reported. The aim of the current study is to evaluate the effectiveness of the clay kaolin in the laboratory and in the field in reducing the damage caused by the eulophid Ophelimus maskelli (Ashmead) on seedlings of eucalyptus (Eucalyptus L'Hér.) species. In the laboratory, kaolin wetting agent significantly reduced the percentage of infested leaves and the number of galls per leaf. In the nursery, gall number per leaf was not correlated with leaf area with kaolin wetting agent but was related to leaf area for all other treatments (wetting agent alone, imidacloprid, and untreated control). In the nursery, gall number per leaf was lower with kaolin wetting agent and with imidacloprid than with the other two treatments. Overall, kaolin effectively reduced eulophid infestations, and its effect was more persistent than that of imidacloprid. Although application of kaolin might not be feasible on large forested areas, kaolin could represent a valuable control method in nurseries, where the repeated application with more toxic chemicals can result in high concentrations of residual pesticides in the soil.
Embryonated eggs of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) genetic sexing strain (GSS), VIENNA 8 were treated with low concentrations of five disinfectants—formaldehyde, iodine, sodium hypochlorite, peracetic acid, and quaternary ammonium—for decontamination and egg hatch improvement. The newly laid eggs were successfully treated with formaldehyde at 100 ppm for 1 min with 74.2% hatching and with quaternary ammonium at 150 ppm for 1 and 2 min with 70.4 and 69% hatching, respectively. Increased formaldehyde concentration may have affected the embryos, because it resulted in a decrease in the hatching percentage. However, egg viability was not impaired and hatch was not affected by quaternary ammonium treatment compared with controls and eggs treated with other disinfectants. Quaternary ammonium shows promise for decontaminating eggs and improving egg hatch.
Spinosad bait is used to control western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), by killing flies before they oviposit. However, effects of different insecticide baits on management of reproductively mature flies are largely unknown. Objectives here were to determine mortality and oviposition of reproductively mature R. indifferens exposed to different insecticide baits for varying periods in the presence and absence of dried yeast extract and sucrose food. Spinosad bait (spinosad in a mix of protein, sugar, and other ingredients) was compared with acetamiprid, thiamethoxam, and imidacloprid in sucrose or Nu-Lure sucrose bait. When flies were exposed to treatments and then offered cherries, Prunus avium (L.) L., for oviposition or when they were exposed to treatments and cherries simultaneously, both thiamethoxam bait and imidacloprid bait resulted in higher mortality and lower oviposition than spinosad bait and acetamiprid bait. Exposures to thiamethoxam bait and imidacloprid bait for six and 24 h were similarly effective, but 6-h exposures to spinosad bait and acetamiprid bait were less effective than 24-h exposures. There was little difference between sucrose and Nu-Lure sucrose baits. When food was present, thiamethoxam bait and imidacloprid bait caused greater mortality and lower oviposition than spinosad bait and acetamiprid bait, but when food was absent, patterns were less consistent. Because of its ability to kill flies sooner after it is exposed to flies when food is present or absent, thiamethoxam or imidacloprid in sucrose or Nu-Lure bait may reduce infestations in cherries more than spinosad bait when mature R. indifferens are present in orchards.
The western chinch bug, Blissus occiduus Barber (Hemiptera: Blissidae), has emerged as a serious pest of buffalograss, Buchloë dactyloides (Nuttall) Engelmann. In general, neonicotinoid insecticides effectively control a variety of turfgrass insects, particularly phloem-feeding pests. However, because of well documented inconsistencies in control, these compounds are generally not recommended for chinch bugs. This study was designed to document the contact and systemic toxicity of three neonicotinoid insecticides (clothianidin, imidacloprid, and thiamethoxam) to B. occiduus. In contact bioassays, thiamethoxam was ≈20-fold less toxic than clothianidin or imidacloprid to B. occiduus nymphs and three-fold more toxic to adults. In adult systemic bioassays, thiamethoxam was up to five-fold more toxic than clothianidin or imidacloprid. Interestingly, thiamethoxam was significantly more toxic to adults than to nymphs in both contact and systemic bioassays. This was not observed with clothianidin or imidacloprid. Bifenthrin, used for comparative purposes, exhibited 1,844-fold and 122-fold increase in toxicity to nymphs and adults, respectively. These results provide the first documentation of the relative toxicity of these neonicotinoid insecticides to B. occiduus.
Egg traps are the primary tool for monitoring egg deposition of the navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), and for timing treatments for this pest in almonds, Prunus amygdalus Batsch, and pistachios, Pistacia vera L. We compared, in almond and pistachio orchards, the number of eggs per trap in traps baited with almond meal, pistachio meal, or the current standard commercial bait. When considering cumulative eggs captured over an extended period, traps baited with pistachio meal prepared from previous-crop nuts generally captured a similar number of eggs compared with the commercial bait, and more eggs than those baited with almond meal prepared from previous-crop nuts. However, differences in eggs per trap between bait formulations were not as evident when examining individual weeks, particularly in weeks with few eggs per trap, as is typical when treatment decisions are made. The variance in eggs per trap was generally greater than the mean and increased with the mean and, when mean eggs per trap was low, most traps did not have eggs. We discuss implications of these findings for the relative importance of bait type and trap numbers for monitoring, and for experiments comparing egg trap performance.
The aim of the research was to identify efficacious and less environmentally harmful treatments than the standard chlorpyrifos sprays used for the control light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), eggs on nursery stock. A series of dip experiments showed a range of responses when comparing the efficacy of insecticides on egg hatch of E.postvittana. The insecticides that compared most favorably with chlorpyrifos were λ-cyhalothrin and γ-cyhalothrin, and thiacloprid. Indoxacarb, novaluron, and spinosad caused significant mortality only when combined with All Seasons mineral oil. All Seasons, showed ovicidal properties when evaluated alone and demonstrated adjuvant properties when combined with the above-mentioned insecticides, except γ-cyhalothrin and thiacloprid. Several other horticultural mineral oils performed similarly, except the efficacy of spinosad varied with the oil product used, suggesting that the oil type selected is important for some insecticide and oil combinations. Several insecticides evaluated in this study are likely candidates for further work to develop treatments against E. postvittana eggs on nursery plants. Mineral oils are ovicidal and combinations with insecticides are likely to be advantageous.
In this investigation, detection dogs are trained and used in identifying red imported fire ants, Solenopsis invicta Buren, and their nests. The methodology could assist in reducing the frequency and scope of chemical treatments for red imported fire ant management and thus reduce labor costs and chemical use as well as improve control and quarantine efficiency. Three dogs previously trained for customs quarantine were retrained to detect the scents of red imported fire ants. After passing tests involving different numbers of live red imported fire ants and three other ant species—Crematogaster rogenhoferi Mayr, Paratrechina longicornis Latreille, and Pheidole megacephala F.—placed in containers, a joint field survey for red imported fire ant nests by detection dogs and bait traps was conducted to demonstrate their use as a supplement to conventional detection methods. The most significant findings in this report are 1) with 10 or more red imported fire ants in scent containers, the dogs had >98% chance in tracing the red imported fire ant. Upon the introduction of other ant species, the dogs still achieved on average, a 93% correct red imported fire ant indication rate. Moreover, the dogs demonstrated great competence in pinpointing emerging and smaller red imported fire ant nests in red imported fire ant-infested areas that had been previously confirmed by bait trap stations. 2) Along with the bait trap method, we also discovered that ≈90% of red imported fire ants foraged within a distance of 14 m away from their nests. The results prove detection dogs to be most effective for red imported fire ant control in areas that have been previously treated with pesticides and therefore containing a low density of remaining red imported fire ant nests. Furthermore, as a complement to other red imported fire ant monitoring methods, this strategy will significantly increase the efficacy of red imported fire ant control in cases of individual mount treatment.
Termites (Isoptera) have often been proposed as decomposers of lignocellulosic waste, such as paper products, while termite biomass could be harvested for food supplements. Groups of Coptotermes formosanus Shiraki and Reticulitermes speratus (Kolbe) were kept for 4 and 8 wk, respectively, in the laboratory and given up to 10 different types of paper as their food source. Paper consumption, survival, caste composition, and lipid content were recorded. Corrugated cardboard was by far the most consumed paper product, although survival on it was not necessarily favorable. In R. speratus, lipid reserves and neotenic numbers were quite high, but no breeding occurred. Cardboard may be the “junk food” equivalent for termites. Within the tested period, termites did not perform well on paper products that form the bulk of waste paper—corrugated cardboard, newsprint, and pamphlets and magazines. On all paper products (except recycled office paper), neotenic reproductives were formed, but larvae were observed only on kraft pulp and tissue paper. That all waste paper products contain lignocellulosic fibers does not automatically make them suitable for decomposition by termites. Each paper product has to be assessed on its own merit to see whether termites can reproduce on this diet, if it were to be a candidate for sustainable “termidegradation” and termite biomass production.
The resistant (R) strain of the planthopper Nilaparvata lugens (Stål) selected for bisultap resistance displayed 7.7-fold resistance to bisultap and also had cross-resistance to nereistoxin (monosultap, thiocyclam, and cartap), chlorpyrifos, dimethoate, and malathion but no cross-resistance to buprofezin, imidacloprid, and fipronil. To find out the biochemical mechanism of resistance to bisultap, biochemical assay was done. The results showed that cytochrome P450 monooxygenases (P450) activity in R strain was 2.71-fold that in susceptible strain (S strain), in which the changed activity for general esterase (EST) was 1.91 and for glutathione S-transferases only 1.32. Piperonyl butoxide (PBO) could significantly inhibit P450 activity (percentage of inhibition [PI]: 37.31%) in the R strain, with ESTs PI = 16.04% by triphenyl phosphate (TPP). The results also demonstrated that diethyl maleate had no synergism with bisultap. However, PBO displayed significant synergism in three different strains, and the synergism increased with resistance (S strain 1.42, Lab strain, 2.24 and R strain, 3.23). TPP also showed synergism for three strains, especially in R strain (synergistic ratio = 2.47). An in vitro biochemical study and in vivo synergistic study indicated that P450 might be play important role in the biochemical mechanism of bisultap resistance and that esterase might be the important factor of bisultap resistance. Acetylcholinesterase (AChE) insensitivity play important role in bisultap resistance. We suggest that buprofezin, imidacloprid, and fipronil could be used in resistance management programs for N. lugens via alternation and rotation with bisultap.
The insect sodium channel is of particular interest for evaluating resistance to pyrethroids because it is the target molecule for this major class of neurotoxic insecticides. The stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), sodium channel coding sequence representing domains IS6 through IVS6 was isolated, and the sequence encoding domain II was compared among individuals of a laboratory strain selected for resistance to permethrin and the unselected, parental generation. A point mutation resulting in a leucine-to-histidine amino acid change was identified (Leu1014His), and its location corresponded with that observed for knockdown resistance (kdr) mutations in other insects. As a result, the allele was designated kdr-his. A molecular assay was developed to assess the frequency of this mutation in genomic DNA of individual stable flies from the laboratory selections, which provided further evidence that the kdr-his allele accounts for the observed level of permethrin resistance in the selected strain. The assay was then used to evaluate the frequency of the mutation from five field-collected populations originating from three horse farms near Ocala, FL; one horse farm near Gainesville, FL; and one dairy farm near Hague, FL. Frequency of the kdr-his allele ranged from 0.46 to 0.78, supporting further investigation of allele prevalence throughout the stable fly season and in response to field insecticide application.
The horn fly, Haematobia irritans (L.) (Diptera: Muscidae), was introduced to Chile in the beginning of the 1990s. Since its introduction, farmers have controlled this pest almost exclusively with insecticides. To understand the consequences of different control strategies on the development of insecticide resistance and their persistence, a field survey was conducted at eight farms in the south of Chile to characterize insecticide resistance in field populations and resistance mechanisms. Horn fly samples were assayed to determine levels of resistance to pyrethroids and diazinon, genotyped for kdr and HiαE7 mutations, and tested for general esterase activity. All field populations, including ones that were not treated with insecticides for the past 5 yr, showed high levels of cypermethrin resistance and high frequencies of the kdr mutation. None of the fly populations demonstrated resistance to diazinon and the HiαE7 mutation was not detected in any of the fly samples. Esterase activities in all populations were comparable to those found in the susceptible reference strain. The findings of high frequencies of homozygous resistant and heterozygous individuals both in insecticide treated horn fly populations and in the untreated fly populations suggests complex interactions among field populations of the horn fly in Chile.
To set up a sterile male technique program to control Aedes albopictus (Skuse) in areas in northern Italy, a pilot mass-rearing facility is under development. For this purpose, experiments were carried out to find the optimal larval density for the optimization of the rearing parameters, i.e., to obtain the fastest larval development, the highest larval and pupal survival rate, and large-sized pupae. Several different larval densities, from 40 to 2,874 larvae per liter, were tested. For densities from 40 to 600 larvae per liter significant size differences were found among pupae obtained under different larval densities. The larvae raised at the lowest density tended to be smaller and to develop most slowly, i.e., longer pupation time. Also, increasing water volume and depth seemed to negatively affect the pupation success. Compared with the other larval densities tested, the larvae reared at a density of 2,874 larvae per liter developed slightly faster and showed higher survival rates, indicating this density as appropriate for the development of a mass rearing, at least using the current larval diet.
Bed bugs, Cimex lectularius L., are now considered a serious urban pest in the United States. Because they are small and difficult to find, there has been strong interest in developing and using monitoring tools to detect bed bugs and evaluate the results of bed bug control efforts. Several bed bug monitoring devices were developed recently, but their effectiveness is unknown. We comparatively evaluated three active monitors that contain attractants: CDC3000, NightWatch, and a home-made dry ice trap. The Climbup Insect Interceptor, a passive monitor (without attractants), was used for estimating the bed bug numbers before and after placing active monitors. The results of the Interceptors also were compared with the results of the active monitors. In occupied apartments, the relative effectiveness of the active monitors was: dry ice trap > CDC3000 > NightWatch. In lightly infested apartments, the Interceptor (operated for 7 d) trapped similar number of bed bugs as the dry ice trap (operated for 1 d) and trapped more bed bugs than CDC3000 and NightWatch (operated for 1 d). The Interceptor was also more effective than visual inspections in detecting the presence of small numbers of bed bugs. CDC3000 and the dry ice trap operated for 1 d were equally as effective as the visual inspections for detecting very low level of infestations, whereas 1-d deployment of NightWatch detected significantly lower number of infestations compared with visual inspections. NightWatch was designed to be able to operate for several consecutive nights. When operated for four nights, NightWatch trapped similar number of bed bugs as the Interceptors operated for 10d after deployment of NightWatch. We conclude these monitors are effective tools in detecting early bed bug infestations and evaluating the results of bed bug control programs.
The genetic structure of 23 populations of Graphocephala atropunctata (Signoret) (Hemiptera: Cicadellidae: Cicadellinae), a vector of the plant pathogenic bacterium Xylella fastidiosa Wells et al., was investigated using ribosomal 28S and mitochondrial cytochrome C oxidase I gene sequences. The 28S sequences were identical across all G. atropunctata specimens and populations, but 16 mitochondrial haplotypes were detected and significant interpopulation differences were found in the distribution of these haplotypes. Pairwise estimates of Fst correlated positively with geographical distance between populations, a phenomenon known as genetic isolation by distance. Thus, despite potential for widespread movement of G. atropunctata through nursery and agricultural industries, isolated populations of G. atropunctata have remained genetically distinct, suggesting that negligible numbers of G. atropunctata are actually transported or population interbreeding rarely occurs. The phylogenetic relationship between G. atropunctata and two additional congeners, Graphocephala cythura Baker and Graphocephala flavovittata Metcalf, which have overlapping distributions with G. atropunctata, also was investigated. Although 28S sequences of G. flavovittata were strikingly similar to those of G. atropunctata, mitochondrial DNA (mtDNA) suggests that both species are genetically distinct from G. atropunctata.
Understanding how fertilization affects host resistance to hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), is important because fertilizers are often used to grow resistant selections to a suitable size for testing. We evaluated four hemlock species (Tsuga) under three different fertilizer regimes to assess whether fertility affected resistance to the adelgid and to determine whether it affected feeding preferences of the adelgid predators Laricobius nigrinus Fender and Sasajiscymnus tsugae (Sasaji & McClure). Treatments were long-term fertilization (from June 2008 to June 2009), short-term fertilization (from March to June 2009), and no fertilizer. Fertilizer was applied biweekly with 240 ppm N by using water-soluble fertilizer (N-P-K, 20:20:20). Plants (>1 yr old) were artificially infested with adelgids on 31 March 2009. Among unfertilized hemlocks (n = 10 per species), foliar N was highest in Tsuga mertensiana (Bong.) Carrière and lowest in T. chinensis (Franch.) E. Pritz. Significantly more progredien ovisacs or sisten eggs were present on T. mertensiana than on the other hemlock species with none on unfertilized T.chinensis. A. tsugae adults on T. heterophylla (Raf.) Sarg. were unaffected by fertility, but densities of developing A.tsugae nymphs were higher on unfertilized T.heterophylla plants than on fertilized T. heterophylla plants regardless of fertilizer treatment. Both L. nigrinus and S.tsugae consumed more adelgid eggs that developed on fertilized T.canadensis than from unfertilized plants. The predators did not exhibit this preference for adelgid eggs from females that developed on T. heterophylla or T. mertensiana.
Several maize, Zea mays L., inbred lines developed from an Antiguan maize population have been shown to exhibit resistance to numerous aboveground lepidopteran pests. This study shows that these genotypes are able to significantly reduce the survival of two root feeding pests, western corn rootworm, Diabrotica virgifera virgifera LeConte, and southern corn rootworm, Diabrotica undecimpunctata howardi Barber. The results also demonstrated that feeding by the aboveground herbivore fall armyworm, Spodoptera frugiperda (J.E. Smith), before infestation by western corn rootworm reduced survivorship of western corn rootworm in the root tissues of some, but not all, genotypes. Likewise, the presence of western corn rootworm in the soil seemed to increase resistance to fall armyworm in the whorl in several genotypes. However, genotypes derived from the Antiguan germplasm with genetic resistance to lepidopterans were still more resistant to the fall armyworm and both rootworm species than the susceptible genotypes even after defense induction. These results suggest that there may be intraplant communication that alters plant responses to aboveground and belowground herbivores.
Field experiments were conducted in steel bins containing 13,600 kg of hard red winter wheat, Triiticum aestivum L. One bin was treated with ozone and the second bin served as a control. Stored grain insects were placed in bins for 1-, 2-, 3-, and 4-d exposure periods in sampling tubes to test ozone concentrations of 0, 25, 50, and 70 parts per million by volume (ppmv). Ozone treatments on eggs and larvae of Plodia interpunctella (Hübner) were not effective, but pupae were more susceptible. Sitophilus oryzae (L.) adults were the most susceptible species with 100% mortality reached after 2 d in all ozone treatments. However, some progeny were produced at all concentrations and exposure periods. Tribolium castaneum (Herbst) adults had 100% mortality only after 4 d at 50 or 70 ppmv. No T. castaneum progeny were produced after 2–4 d at 70 ppmv. For Rhyzopertha dominica (F.), Cryptolestes ferrugineus (Stephens), and Oryzaephilus surinamensis (L.), 100% mortality was never achieved and progeny were produced at all ozone concentrations. Laboratory experiments, testing the effectiveness of ozone in controlling psocids, were conducted in two polyvinyl chloride cylinders each containing 55 kg of hard red winter wheat. Ozone treatment at a concentration of 70 ppmv was highly effective against adult female Liposcelis bostrychophila Badonnel and Liposcelis paeta Pearman after only 1 d of exposure. However, it was not effective against eggs of both species at all exposure periods. Ozonation has potential for the control of some stored grain insect pests on wheat.
Heat treatment of food-processing facilities involves using elevated temperatures (50– 60°C for 24–36 h) for management of stored-product insects. Heat treatment is a viable alternative to the fumigant methyl bromide, which is phased out in the United States as of 2005 because of its adverse effects on the stratospheric ozone. Very little is known about responses of the cigarette beetle, Lasioderma serricorne (F.) (Coleoptera: Anobiidae), a pest associated with food-processing facilities, to elevated temperatures. Responses of L. serricorne life stages to elevated temperatures were evaluated to identify the most heat-tolerant stage. Exposure of eggs, young larvae, old larvae, and adults during heat treatment of a food-processing facility did not clearly show a life stage to be heat tolerant. In the laboratory, exposure of eggs, young larvae, old larvae, pupae, and adults at fixed times to 46, 50, and 54°C and 22% RH indicated eggs to be the most heat-tolerant stage. Time-mortality responses at each of these three temperatures showed that the time for 99% mortality (LT99) based on egg hatchability and egg-to-adult emergence was not significantly different from one another at each temperature. Egg hatchability alone can be used to determine susceptibility to elevated temperatures between 46 and 54°C. The LT99 based on egg hatchability and egg-to-adult emergence at 46°C was 605 and 598 min, respectively, and it decreased to 190 and 166 min at 50°C and 39 and 38 min at 54°C An exponential decay equation best described LT99 as a function of temperature for pooled data based on egg hatchability and egg-to-adult emergence. Our results suggest that during structural heat treatments eggs should be used in bioassays for gauging heat treatment effectiveness, because treatments aimed at controlling eggs should be able to control all other L.serricorne life stages.
The susceptibility of various life stages of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), a pest of stored wheat, Triticum aestivum L., to flameless catalytic infrared radiation in the 3–7-µm range was evaluated in the laboratory. Immature stages were collected from flour infested with T. castaneum adults only for 1 d. Stages collected after 1 d represented eggs (collected on day 0); those collected after 7, 14, and 21 d from day 0 represented larvae in different developmental stages, whereas those collected after 24 d represented pupae. Adults (2 wk old) were collected after 42 d. Each of these stages was exposed for 45 or 60 s in 113.5 or 227.0 g of wheat at a distance of 8.0 or 12.7 cm from a bench top infrared emitter. The mean temperatures attained during exposures were measured continuously using a noncontact infrared thermometer connected to a computer. The mean grain temperatures attained increased with an increase in exposure time and were inversely related to distance from the emitter. Grain quantity least influenced mean temperatures attained. Pupae were the least susceptible stage and larvae collected after 7 d were the most susceptible stage. Variation in probability of death of various life stages decreased with an increase in mean grain temperatures attained. All life stages were killed after a 60-s exposure at a distance of 8.0 cm from the emitter in 113.5 g of wheat, where the mean ± SE temperatures attained ranged from 107.6 ± 1.2 to 111.4 ± 0.5°C. Our laboratory results using small grain quantities and short exposure times showed that flameless catalytic infrared radiation can be a valuable tool for managing insects in stored organic and nonorganic wheat.
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