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The invasive kudzu bug, Megacopta cribraria (F.) (Hemiptera: Plataspidae), has become an economic pest of soybean, Glycine max (L.) Merrill, in the southeastern United States since its initial discovery in Georgia. Information on management practices, including insecticides, is limited due to its uncertain pest status in its native range and recent introduction to the United States. We evaluated the efficacy in controlling M. cribraria and economic benefits of a variety of insecticides labeled for use in soybean from different chemical classes in field trials in South Carolina and Georgia from 2010 through 2012. Several pyrethroids were among the most effective insecticides for control of M. cribraria. The pyrethroid bifenthrin had an immediate (2–6 d after treatment application) percentage of control of 97.5 ± 0.2% (SEM), which was the highest of the active ingredients tested. Likewise, net marginal benefits were typically greatest for pyrethroids, either alone or tank-mixed with other materials. Our results confirm that chemical control of M. cribraria in commercial soybean production is economically viable, but the number of effective chemical classes is limited.
Dormant-season applications of copper-containing fungicides and organophosphate insecticides are common in Prunus spp. orchards, and these compounds are often mixed into a single application. However, copper(II) catalyzes the hydrolytic breakdown of many organophosphate insecticides. We measured the impact of tank-mixing these products using field efficacy data collected from 2002 to 2004 coupled with active ingredient degradation studies in the laboratory. Formulations of the organophosphate insecticides chlorpyrifos and diazinon were applied with and without the fungicide Cu(OH)2 in peach orchards, and the resulting peach twig borer (Anarsia lineatella Zeller) damage was measured. Laboratory experiments to quantify the degradation of the active organophosphate ingredient in various dry deposits from treatment solutions showed that addition of Cu(OH)2 to laboratory organophosphate solutions resulted in more rapid degradation of the active organophosphate ingredient in dry deposits stored at 100% relative humidity at room temperature. Unsurprisingly, there was significantly more peach twig borer field damage in chlorpyrifos treatments containing copper than those that excluded copper. However, this was not observed with diazinon. Because copper(II) catalyzes the breakdown of various organophosphate insecticides across a range of pH values, caution should be used with the simultaneous application of copper(II)-containing fungicides/bactericides and organophosphate insecticides.
A two-molecule chitinolytic enzyme system (endo- and exo-chitinase) hydrolyzes and degrades the chitin polymers. Therefore, it is imperative to discover novel compounds for inhibiting chitinolytic enzymes to prevent insect growth. This research examined the effect of pentoxifylline (a dimethylxanthine chitinase inhibitor) on inhibition of endo- and exo-chitinolytic enzyme activities in eastern subterranean termite, Reticulitermes flavipes (Kollar). Enzyme activities were compared with amounts of treated diet consumed by termites and percent mortality observed over time. Pentoxifylline affected in vitro endo-chitinase activity in a concentration-dependent manner, while having minimal to no effect on in vitro exo-chitinase enzyme activity. However, pentoxifylline treatment affected in vivo endo- and exo-chitinase enzyme activity and caused measurable termite mortality. Moreover, pentoxifylline concentrations did not deter the amount of diet consumed by termites, thereby suggesting that it is palatable. The results of this study support further exploration into termiticidal activity and potential use of pentoxifylline for termite control.
The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is an important pest of rice (Oryza sativa L.) grown in Florida. Reports on the effect of flood depth on rice water weevil populations have been inconsistent. Our objective was to determine if flood depth has any significant effect on rice water weevil populations and other arthropods in rice grown in Florida. Sampling was conducted using adult foliar damage scars, core samples for larvae, and sweep nets for arthropods above the water. Results showed that shallow flooding reduced rice water weevil populations in Florida. Sweep net data showed that flood depth had little, if any, effect on populations of damselflies (Odonata), leafhoppers (Cicadellidae), spiders (Arachnida), or stink bugs (Oebalus spp.).
The intensity of ultraviolet (UV) radiation varies widely in space, both across the globe and over small spatial scales (a few millimeters), depending on patterns of light and shade. Gradients of UV radiation can control the movement of organisms on landscapes and how the organisms perform. It is likely that insects are at high risk from UV radiation because of their small size; radiation may penetrate significantly deeper into insect tissues than into larger organisms, thereby disproportionately affecting their performance. We investigated the effects of UV radiation on the behavior and parasitism success of the agriculturally important egg parasitoid wasp, Trichogramma spp. We found that Trichogramma preferred to move toward higher intensities of UV-B radiation and parasitized more eggs in areas with higher UV-B radiation. However, higher UV-B radiation reduced the number of adult wasps emerging from host eggs. Trichogramma reproductive behavior may, therefore, be maladaptive depending on environmental context. These results could be of particular importance in the agricultural release of Trichogramma, especially in greenhouse settings, where levels of UV-B radiation are low.
Diaprepes root weevil, Diaprepes abbreviatus L., was first found in southern California in 2005 and has since spread to citrus groves in a small area of southern California. To develop pest management programs for this pest, its seasonal abundance and distribution of immature stages (including teneral adults) in the soil were investigated. The seasonal abundance of D. abbreviatus adults was monitored with modified Tedders traps. Emergence of D. abbreviatus adults from soil pupation chambers occurred throughout most of the year, and peak emergence occurred from July to October. However, there was no secondary annual peak emergence over the 4 yr of study in California as has been observed in Florida, suggesting diaprepes root weevil is univoltine in southern California's cooler climate. Annual emergence cycles mirrored patterns of air temperature rather than rainfall. Seasonal abundance and the impact of climate on range expansion of diaprepes root weevil are discussed. The effect of the number and arrangement of traps on the number of adult D. abbreviatus caught was also investigated, and we determined that they did not have an effect on adult D. abbreviatus trap catch data. Immature life stages in the soil occurred under the tree drip line within the top 30.5 cm of soil and horizontally up to 96.5 cm from the tree trunk. The majority were observed between 17.8 and 45.7 cm from the crown of the trees, which is in the area of Tedders trap placement.
A photograph-based monitoring system was developed to involve citizen scientists in monitoring sites in western North Carolina and northern Georgia where the predators Sasajiscymnus tsugae (Sasaji & McClure) and Laricobius nigrinus Fender had been released as part of the U.S. Forest Service's biological control program for Adelges tsugae Annand (hemlock woolly adelgid). The study was divided into an initial phase conducted during 2006 and 2007 in Jackson and Macon counties, NC, and Rabun County, GA, and a second phase conducted from 2008 to 2010 in Fannin, Gilmer, Lumpkin, and Union counties, GA. Over the course of the study, 32 volunteers monitored 27 predator release sites and provided 4,356 photographs from which data were obtained. Data from photographs included the number of A. tsugae ovisacs present at each sample site and hemlock needle loss on photographed branches. To ensure accuracy in counting A. tsugae and assessing hemlock needle loss, personnel from Clemson University's A. tsugae insectary evaluated each photograph for data collection. The citizen scientist volunteers participating in this study allowed us to obtain a large amount of quality data from across the wide geographic range of predator release sites. Obtaining that amount of data would not have been possible using only our laboratory personnel. This study shows that including dedicated and properly trained volunteers in large-scale forest surveys was an effective way to dramatically increase the amount of data we could obtain for use in assessing trends in both the numbers of A. tsugae present and hemlock needle loss at predator release sites.
Micromelalopha troglodyta (Graeser) (Lepidoptera: Notodontidae) is an important pest of poplar trees, Populus spp. (family Salicaceae), in China. Herein, we report the first cloning and sequencing of a full-length cDNA of a delta class (Class I) glutathione S-transferase (GST), MtGSTd1, from the larval midgut of M. troglodyta. The open reading frame of the MtGSTd1 cDNA was 657 bp and encoded 219 amino acid residues in M. troglodyta. Furthermore, specific activities of GSTs were induced in fat bodies and midguts of M. troglodyta by tannic acid. MtGSTd1 mRNA also was induced by tannic acid in the fat bodies and midguts. GST activities increased following the elevated expression of GST mRNA in M. troglodyta. These findings indicate that the GSTs may have an antioxidant role in the metabolism of plant secondary substances in M. troglodyta larvae.
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