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Background: Widespread reports of reduced efficacy of imidacloprid for managing cotton aphids (Aphis gossypii Glover) in cotton (Gossypium hirsutum L.) prompted an investigation to characterize the susceptibility of 43 populations over a 2-year period. The susceptibility of A. gossypii populations to imidacloprid was examined by calculating LC50 values. Further analyses related resistance assay results to a gradient of cotton production intensity., Results: Concentration-mortality bioassays documencted populations that were 4.26-607.16 times more resistant than the susceptible laboratory population. There was a significant positive relationship between LC 50 values and percentage of cotton within 2.5- and 5-km buffers surrounding collection sites. No significant relationship was detected between LC 50 values and the percentage of alternative crop and noncrop hosts., Conclusion: Variable and high levels of resistance were detected in A. gossypii populations, and this variation was positively associated with cotton production intensity. Cotton is a host that may receive multiple applications of neonicotinoids (via seed treatment and foliar sprays) annually for seedling and mid-season pests. Rotating modes of action and limiting insecticide use should be implemented to delay the evolution of insecticide resistance in A. gossypii populations. © 2022 Society of Chemical Industry., (© 2022 Society of Chemical Industry.)

Foliar-applied insecticide treatments may be necessary to manage thrips in cotton (Gossypium hirsutum L.) under severe infestations or when at-planting insecticide seed treatments do not provide satisfactory protection. The most common foliar-applied insecticide is acephate. Field observations in Tennessee suggest that the performance of acephate has declined. Thus, the first objective was to perform leaf-dip bioassays to assess if tobacco thrips, Frankliniella fusca (Hinds) (Thysanoptera: Thripidae), in cotton production regions have evolved resistance to foliar-applied insecticides. A second objective was to assess the performance of commonly applied foliar insecticides for managing thrips in standardized field trials in Arkansas, Tennessee, Mississippi, and Texas. For both objectives, several insecticides were evaluated including acephate, dicrotophos, dimethoate, lambda-cyhalothrin, imidacloprid, and spinetoram. Field trials and bioassays were completed from 2018 to 2021. Dose-response bioassays with acephate were performed on tobacco thrips field populations and a susceptible laboratory population. Bioassay results suggest that tobacco thrips have developed resistance to acephate and other organophosphate insecticides; however, this resistance seems to be most severe in Arkansas, Tennessee, and the Delta region of Mississippi. Resistance to other classes of insecticides were perhaps even more evident in these bioassays. The performance of these insecticides in field trials was variable, with tobacco thrips only showing consistent signs of resistance to lambda-cyhalothrin. However, it is evident that many populations of tobacco thrips are resistant to multiple classes of insecticides. Further research is needed to determine heritability and resistance mechanism(s)., (© The Author(s) 2022. Published by Oxford University Press on behalf of Entomological Society of America.)

Transgenic cotton expressing Cry51Aa2.834_16 Bt toxin (hereafter referred to as MON 88702) has the potential to be an important tool for pest management due to its unique activity against tobacco thrips, Frankliniella fusca. Unlike other Bt toxins targeting lepidopteran cotton pests, MON 88702 does not cause direct mortality but has an antixenotic effect that suppresses F. fusca oviposition. Previous work has shown neonicotinoid seed treated (NST) crops have similar behavioral effects on thrips. This study used non-choice and common garden experiments to examine how the presence of MON 88702 cotton and soybean (another F. fusca host) with and without NSTs might alter F. fusca infestation distributions. In a no-choice environment, significant larval establishment differences were observed, with untreated soybean plants becoming most heavily infested. In choice experiments, plants expressing MON 88702 or were neonicotinoid treated had significantly lower larval establishment. Larval density decreased as dispersal distance increased, suggesting reproductive decisions were negatively related to distance from the release point. Understanding how F. fusca responds to MON 88702 in an environment where adults can choose among multiple host plants will provide valuable context for projections regarding design of MON 88702 resistance refuges. Reduced larval establishment on NST cotton and soybean suggests that area-wide use of NSTs could reduce the number of susceptible F. fusca generated in unstructured crop refuges for MON 88702. These results also suggest that although the presence of NST MON 88702 could suppress reproduction and resistance selection, over time this benefit could erode resulting in increased larval establishment on NST cotton and soybean due to increased frequency of neonicotinoid resistant F. fusca populations., Competing Interests: The authors have read the journal’s policy and have the following potential competing interests: AH and GK received support from Bayer Crop Science in the form of crop seed and initial funding to generate information for this study. This does not alter our adherence to PLOS ONE policies on sharing data and materials. There are no patents, products in development or marketed products associated with this research to declare.

Background: Insecticide resistance arises at a given location in response to selection acting on novel genotypes or standing variation, or allelic migration. Fitness costs of resistance may slow resistance evolution or result in reversion to susceptibility, but consistent and geographically widespread use of insecticides may provide sufficient selection to offset the fitness costs of resistance. Understanding this relationship is important to the success of insecticide resistance management. We report the existence of fitness costs of neonicotinoid resistance in field-collected populations of the tobacco thrips (Frankliniella fusca), which increasingly challenge upland cotton production in the southeastern USA., Results: Populations (14 of 15 in 2015; 4 of 5 in 2016) investigated showed a loss of resistance to imidacloprid after multiple generations without exposure to the insecticide. Populations studied in 2016 were each split into two colonies, and one of each pair was repeatedly exposed to imidacloprid. In three of the four populations that lost resistance, imidacloprid-exposed colonies lost resistance significantly more slowly than did corresponding unexposed colonies., Conclusion: For imidacloprid resistance to be broadly increasing in the landscapes of the southeastern USA despite fitness costs of resistance, selection for resistance must be sufficient to overcome the costs. Findings encourage investigation into why costs are overcome in this system, potentially including geographic extent of neonicotinoid use or prevalence of low-dose exposure. © 2019 Society of Chemical Industry., (© 2019 Society of Chemical Industry.)

Neonicotinoids are a popular and widely-used class of insecticides whose heavy usage rates and purported negative impacts on bees and other beneficial insects has led to questions about their mobility and accumulation in the environment. Neonicotinoid compounds are currently registered for over 140 different crop uses in the United States, with commercial growers continuing to rely heavily on neonicotinoid insecticides for the control of key insect pests through a combination of in-ground and foliar applications. In 2008, the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) began testing for neonicotinoids in groundwater test wells in the state, reporting detections of one or more neonicotinoids in dozens of shallow groundwater test wells. In 2011, similar detection levels were confirmed in several high-capacity overhead center-pivot irrigation systems in central Wisconsin. The current study was initiated to investigate the spatial extent and magnitude of neonicotinoid contamination in groundwater in and around areas of irrigated commercial agriculture in central Wisconsin. From 2013-2015 a total of 317 samples were collected from 91 unique high-capacity irrigation wells and tested for the presence of thiamethoxam (TMX), a neonicotinoid, using enzyme-linked immunosorbent assays. 67% of all samples were positive for TMX at a concentration above the analytical limit of quantification (0.05 μg/L) and 78% of all wells tested positive at least once. Mean detection was 0.28 μg/L, with a maximum detection of 1.67 μg/L. Five wells had at least one detection exceeding 1.00 μg/L. Furthermore, an analysis of the spatial structure of these well detects suggests that contamination profiles vary across the landscape, with differences in mean detection levels observed from landscape (25 km), to farm (5 km), to individual well (500 m) scales. We also provide an update of DATCP's neonicotinoid monitoring in Wisconsin's shallow groundwater test wells and private potable wells for the years 2011-2017., Competing Interests: The authors have declared that no competing interests exist.

The intensification of industrial agriculture has been enabled by improved crop varieties, genetically engineered crops, fertilizers, and pesticides. Over the past 15 years, neonicotinoid seed treatments have been adopted worldwide and are used on a large proportion of U.S. field crops. Although neonicotinoids are used widely, little is known about how large-scale deployment affects pest populations over long periods. Here, we report a positive relationship between the deployment of neonicotinoid seed-dressings on multiple crops and the emergence of insecticide resistance in tobacco thrips (Frankliniella fusca), a polyphagous insect herbivore that is an important pest of seedling cotton but not soybean or maize. Using a geospatial approach, we studied the relationship between neonicotinoid resistance measured in 301 F. fusca populations to landscape-scale crop production patterns across nine states in the southeastern U.S. cotton production region, in which soybean, maize and cotton are the dominant crops. Our research linked the spatiotemporal abundance of cotton and soybean production to neonicotinoid resistance in F. fusca that is leading to a dramatic increase in insecticide use in cotton. Results demonstrate that cross-crop resistance selection has important effects on pests and, in turn, drives pesticide use and increases environmental impacts associated with their use.

Background: Detection of neonicotinoid resistance in populations of tobacco thrips, Frankliniella fusca Hinds, throughout the southeastern USA has motivated an examination of alternative insecticides to control problematic infestations on seedling cotton. The objective of this study was to refine understanding of stage-specific mortality and reduced oviposition of several common insecticides (acephate, abamectin, cyantraniliprole, spinetoram, imidacloprid, imidacloprid+thiodicarb, thiamethoxam) on neonicotinoid resistant and susceptible F. fusca populations under laboratory and field conditions., Results: Laboratory studies revealed that the average number of eggs per female and larval or adult survivorship responses differed by insecticide and were dependent on the resistance status of the population. In the presence of neonicotinoids, the resistant F. fusca populations exhibited lower mortality and higher egg counts than the susceptible population. In the field study, similar patterns of oviposition suppression were observed, indicating that some insecticides may impact reproductive rate., Conclusion: This study shows that insecticides have different effects on F. fusca oviposition events, larval and adult mortality that are dependent on neonicotinoid resistance status. Because insecticides tested in this study have varied activity on specific F. fusca life stages (e.g. oviposition suppression, larvicidal activity, adulticidal activity), knowledge of stage-specific activity can be used to improve control and enhance long-term product stewardship. © 2017 Society of Chemical Industry., (© 2017 Society of Chemical Industry.)

The Colorado potato beetle, Leptinotarsa decemlineata (Say), is a major agricultural pest of potatoes in the Central Sands production region of Wisconsin. Previous studies have shown that populations of L. decemlineata have become resistant to many classes of insecticides, including the neonicotinoid insecticide, imidacloprid. Furthermore, L. decemlineata has multiple mechanisms of resistance to deal with a pesticide insult, including enhanced metabolic detoxification by cytochrome p450s and glutathione S-transferases. With recent advances in the transcriptomic analysis of imidacloprid susceptible and resistant L. decemlineata populations, it is possible to investigate the role of candidate genes involved in imidacloprid resistance. A recently annotated transcriptome analysis of L. decemlineata was obtained from select populations of L. decemlineata collected in the Central Sands potato production region, which revealed a subset of mRNA transcripts constitutively up-regulated in resistant populations. We hypothesize that a portion of the up-regulated transcripts encoding for genes within the resistant populations also encode for pesticide resistance and can be suppressed to re-establish a susceptible phenotype. In this study, a discrete set of three up-regulated targets were selected for RNA interference experiments using a resistant L. decemlineata population. Following the successful suppression of transcripts encoding for a cytochrome p450, a cuticular protein, and a glutathione synthetase protein in a select L. decemlineata population, we observed reductions in measured resistance to imidacloprid that strongly suggest these genes control essential steps in imidacloprid metabolism in these field populations., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Over the past two decades, neonicotinoid seed treatments have become the primary method to manage tobacco thrips, Frankliniella fusca Hinds, on seedling cotton. Because this insect is highly polyphagous and the window of insecticide exposure is short, neonicotinoid resistance was expected to pose a minimal risk. However, reports of higher than expected F. fusca seedling damage in seed-treated cotton fields throughout the Mid-South and Southeast US production regions suggested neonicotinoid resistance had developed. To document this change, F. fusca populations from 86 different locations in the eastern United States were assayed in 2014 and 2015 for imidacloprid and thiamethoxam resistance to determine the extent of the issue in the region., Results: Approximately 57 and 65% of the F. fusca populations surveyed had reduced imidacloprid and thiamethoxam sensitivity respectively. Survivorship in diagnostic bioassays was significantly different at both the state and regional scales. Multiple-dose bioassays conducted on 37 of the populations documented up to 55- and 39-fold resistance ratios for imidacloprid and thiamethoxam respectively., Conclusion: Estimates of neonicotinoid resistance indicate an emerging issue for management of F. fusca in the eastern United States. Significant variation in survivorship within states and regions indicated that finer-scale surveys were needed to determine factors (genetic, insecticide use) driving resistance evolution. © 2016 Society of Chemical Industry., (© 2016 Society of Chemical Industry.)

Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), is a highly destructive pest of onion, Allium cepa L., and its management relies on multiple applications of foliar insecticides. Development of insecticide resistance is common in T. tabaci populations, and new strategies are needed to relax existing levels of insecticide use, but still provide protection against T. tabaci without compromising marketable onion yield. An action threshold-based insecticide program combined with or without a thrips-resistant onion cultivar was investigated as an improved approach for managing T. tabaci infestations in commercial onion fields. Regardless of cultivar type, the average number of insecticide applications needed to manage T. tabaci infestations in the action-threshold based program was 4.3, while the average number of sprays in the standard weekly program was 7.2 (a 40% reduction). The mean percent reduction in numbers of applications following the action threshold treatment in the thrips-resistant onion cultivar, 'Advantage', was 46.7% (range 40-50%) compared with the standard program, whereas the percentage reduction in applications in action threshold treatments in the thrips-susceptible onion cultivar, 'Santana', was 34.3% (range 13-50%) compared with the standard program, suggesting a benefit of the thrips-resistant cultivar. Marketable bulb yields for both 'Advantage' and 'Santana' in the action threshold-based program were nearly identical to those in the standard program, indicating that commercially acceptable bulb yields will be generated with fewer insecticide sprays following an action threshold-based program, saving money, time and benefiting the environment., (© The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Background: Multiple applications of pyrethroid insecticides are used to manage European corn borer, Ostrinia nubilalis Hübner, in snap bean, but new diamide insecticides may reduce application frequency. In a 2 year small-plot study, O. nubilalis control was evaluated by applying cyantraniliprole (diamide) and bifenthrin (pyrethroid) insecticides at one of three phenological stages (bud, bloom and pod formation) of snap bean development. Co-application of these insecticides with either herbicides or fungicides was also examined as a way to reduce the total number of sprays during a season., Results: Cyantraniliprole applications timed either during bloom or during pod formation controlled O. nubilalis better than similar timings of bifenthrin. Co-applications of insecticides with fungicides controlled O. nubilalis as well as insecticide applications alone. Insecticides applied either alone or with herbicides during bud stage did not control this pest., Conclusion: Diamides are an alternative to pyrethroids for the management of O. nubilalis in snap bean. Adoption of diamides by snap bean growers could improve the efficiency of production by reducing the number of sprays required each season., (© 2015 Society of Chemical Industry.)

Background: Select populations of Colorado potato beetle, Leptinotarsa decemlineata, in Wisconsin have recently become resistant to soil-applied neonicotinoids in potato. Sublethal insecticide concentrations persisting in foliage through the growing season may select for resistance over successive years of use. Over the 2 years of this study, the aim was to document the in-plant insecticide concentrations over time that result from four different types of soil-applied insecticide delivery for thiamethoxam and imidacloprid in potato, and to measure the impact upon L. decemlineata populations following treatments. After plant emergence, insect life stages were counted and plant tissue was assayed weekly for nine consecutive weeks using ELISA., Results: Peak concentration of both imidacloprid and thiamethoxam occurred in the first sample week following plant emergence. The average concentration of both insecticides dissipated sharply over time as the plant canopy expanded 50 days after planting in all delivery treatments. Both insecticides were detected at low levels during the later weeks of the study. Among-plant concentrations of both neonicotinoids were highly variable throughout the season. Populations of L. decemlineata continued to develop and reproduce throughout the period of declining insecticide concentrations., Conclusion: Sublethal, chronic exposure to soil-applied systemic insecticides resulting from these delivery methods may accelerate selection for resistant insects in potato., (© 2014 Society of Chemical Industry.)

Since 1995, neonicotinoid insecticides have been a critical component of arthropod management in potato, Solanum tuberosum L. Recent detections of neonicotinoids in groundwater have generated questions about the sources of these contaminants and the relative contribution from commodities in U.S. agriculture. Delivery of neonicotinoids to crops typically occurs as a seed or in-furrow treatment to manage early season insect herbivores. Applied in this way, these insecticides become systemically mobile in the plant and provide control of key pest species. An outcome of this project links these soil insecticide application strategies in crop plants with neonicotinoid contamination of water leaching from the application zone. In 2011 and 2012, our objectives were to document the temporal patterns of neonicotinoid leachate below the planting furrow following common insecticide delivery methods in potato. Leaching loss of thiamethoxam from potato was measured using pan lysimeters from three at-plant treatments and one foliar application treatment. Insecticide concentration in leachate was assessed for six consecutive months using liquid chromatography-tandem mass spectrometry. Findings from this study suggest leaching of neonicotinoids from potato may be greater following crop harvest in comparison to other times during the growing season. Furthermore, this study documented recycling of neonicotinoid insecticides from contaminated groundwater back onto the crop via high capacity irrigation wells. These results document interactions between cultivated potato, different neonicotinoid delivery methods, and the potential for subsurface water contamination via leaching.

The invasive Melanaphis sorghi (Theobald; =Melanaphis sacchari Zehntner) is a serious pest of sorghum production in the southern USA. Demonstration of technologies that provide effective control is key to management of this pest. Here, we investigated the effect of host plant resistance (resistant cultivar: DKS37-07 and susceptible cultivar: DKS53-53) and a single foliar insecticide (flupyradifurone: Sivanto Prime) application on M. sorghi infestations and the role of natural enemy populations in grain sorghum production across five locations in four states in southeastern USA. Foliar insecticide application significantly suppressed M. sorghi infestations on both the resistant and susceptible sorghum cultivars across all locations. Planting the host plant resistant cultivar (DKS37-07) significantly reduced aphid infestation across all locations. Plant damage ratings did not vary widely, but there was generally a positive association between aphid counts and observed plant damage, suggesting that increasing aphid numbers resulted in corresponding increase in plant damage. Planting a host plant resistant cultivar and foliar insecticide application generally preserved grain yield. Both sorghum hybrids supported an array of different life stages of natural enemies (predators [lady beetle larvae and adults; hoverfly larvae and lacewing larvae] and parasitoids [a braconid and aphelinid]) for both the sprayed and non-sprayed treatments. We found a strong and significant positive relationship between the natural enemies and the M. sorghi infestation. Results suggest that planting a host plant resistant cultivar and the integration of natural enemies with insecticide control methods in the management of M. sorghi is central to the development of an effective pest management strategy against this invasive pest. [ABSTRACT FROM AUTHOR]

Background Frankliniella fusca (Hinds) resistance to neonicotinoid seed treatments (NSTs) used in cotton has created a need for more diverse insecticide options targeting thrips. Alternative insecticides must protect seedlings while they are most vulnerable to F. fusca injury (emergence through five true leaves). In this study, we evaluated non-neonicotinoid foliar insecticide sprays currently registered for use on cotton against a neonicotinoid resistant F. fusca population. Methods During two-seasons, we compared NSTs (imidacloprid, imidacloprid + thiodicarb, and thiamethoxam) to non-neonicotinoid foliar sprays of acephate, spinetoram, abamectin, cyantraniliprole, and cyantraniliprole + abamectin in field trials to evaluate their efficacy against a neonicotinoid resistant F. fusca population. Applications were made to both early- and full-maturity cotton varieties (Stoneville 4946GLB2 & 6448GLB2) to examine F. fusca larval establishment, plant vigor, and seed cotton yield. Results With the exception of abamectin, foliar insecticide treatments consistently reduced F. fusca larval numbers and minimized true leaf damage at a level equal to or greater than NSTs. Yield was not affected by insecticide treatment. Non-neonicotinoid foliar sprays have utility in managing neonicotinoid-resistant F. fusca and should be recommended to alleviate selection pressure against NSTs in cotton and unnecessary economic losses due to ineffective NST use against resistant F. fusca populations. [ABSTRACT FROM AUTHOR]

The sugarcane aphid, Melanaphis sacchari is an important pest of grain sorghum (Sorghum bicolor) in the United States. Current M. sacchari management programs aim to control M. sacchari with insecticides while minimizing impacts on natural enemies that contribute to biological control of aphid populations. As a result, balancing both insecticide efficacy on the target pest and preservation of biological control agents remains an important step toward sustainable management of M. sacchari in grain sorghum. To document tradeoffs between M. sacchari control and non-target impacts, we evaluated three common aphicides (afidopyropen, flupyradifurone, and sulfoxaflor) for M. sacchari control and natural enemy safety. Treatments were paired with surfactants when recommended. Insect abundance was measured before and after foliar insecticide application using randomized complete clock design small plot studies during the 2019 and 2020 field seasons. All plots were harvested at maturity to document the relationship between in-season aphid abundance and grain yield. In this two year study, the average aphid abundance three days after insecticide application was lower in some but not all insecticidal treatments when compared to the untreated control, suggesting some insecticides had limited aphid suppression capabilities. Mean cumulative aphid days were lower in all treated plots compared to the untreated control with the exception of Sefina (afidopyropen). Twenty-eight days after foliar insecticide application, there were no differences in total natural enemy abundance in any of the treatments including the untreated control, suggesting that while M. sacchari populations were reduced by foliar insecticide treatments, the insecticides did not have clear adverse effects to natural enemy populations. • The impact of three selective insecticides on Melanaphis sacchari was tested. • Most insecticides significantly reduced aphid populations on Sorghum bicolor. • There were limited negative effects of insecticides to natural enemies of M. sacchari. [ABSTRACT FROM AUTHOR]