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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 LC50 values and percentage of cotton within 2.5‐ and 5‐km buffers surrounding collection sites. No significant relationship was detected between LC50 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. [ABSTRACT FROM AUTHOR]

BACKGROUND Tobacco thrips, Frankliniella fusca (Hinds), is a pest of cotton. Currently, growers rely on neonicotinoid seed treatments to control F. fusca. However, the occurrence of neonicotinoid‐resistant F. fusca populations has created new challenges for their management. Development of thrips‐active Cry51Aa2.834_16 Bacillus thuringiensis (Bt) toxin expressed in MON 88702 cotton will be an important new tactic for thrips management. Previous studies have shown that MON 88702 causes limited mortality of F. fusca adults and larvae but reduces infestations on seedling cotton by suppressing oviposition from colonizing adults. This suggests that the toxin affects host preference of adult F. fusca. Knowledge of the effect of this trait on F. fusca feeding behavior provides a more complete understanding of MON 88702 activity. Using electropenetrography, we compared the feeding behaviors of adult F. fusca females on MON 88702 cotton and a non‐Bt isoline cotton over 2 h. The number of probes, proportion of probes resulting in ingestion, total duration of ingestion, and duration of ingestion per event were measured. RESULTS: On MON 88702 seedlings, F. fusca probed and ingested fewer times than those on non‐Bt cotton. Probes on MON 88702 were less likely to lead to ingestion than on non‐Bt cotton. The total duration of ingestion and duration of ingestion per event did not differ between treatments. CONCLUSION: The results show that MON 88702 has an antifeedant effect on F. fusca, which provides insight into behavioral responses driving MON 88702 aversion and anti‐oviposition documented in previous studies. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND: Genetically engineered (GE) crops that express insecticidal traits have improved the sustainability of insect pest management worldwide, but many important pest orders are not controlled by commercially available toxins. Development of the first transgenic thysanopteran‐ and hemipteran‐active Bacillus thuringiensis (Bt) Cry51Aa2.834_16 toxin expressed in MON 88702 cotton will significantly expand the diversity of pests controlled in the crop. Here, we examined MON 88702 cotton activity against two thrips species within the same genera, Frankliniella fusca and Frankliniella occidentalis. We used a multi‐component cotton tissue assay approach to understand effects on adult longevity, fecundity, and larval development. RESULTS: We found that in no‐choice assays, cotton plants expressing MON 88702 suppress oviposition, when compared to a non‐Bt cotton. MON 88702 did not kill a large proportion of F. fusca larvae or adults but killed most F. occidentalis larvae. Time series experiments with F. occidentalis larvae documented significant developmental lags for MON 88702 exposed individuals. We also found that female thrips preferred to oviposit on non‐Bt cotton when provided a choice. CONCLUSION: Together these results describe the activity of MON 88702 against thrips. They document clear differences in toxin performance between different thrips species and throughout the insects' life cycle. Most importantly, we show that MON 88702 was associated with reduced oviposition via behavioral avoidance to the toxin. This is a novel mechanism of action for pest control for a Bt crop plant. Together, these results provide a basis to describe the mechanism of population control for MON 88702 cotton. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Frankliniella fusca (Hinds) (Thysanoptera: Thripidae) is an early-season cotton pest. Seedlings are injured by larvae, which hatch from eggs oviposited into seedlings and feed on developing plant tissue. Better understanding F. fusca oviposition in cotton may improve their management and address new challenges such as resistance to neonicotinoid seed treatments (NSTs). Cotton seedlings exposed to F. fusca were either cleared and stained to determine egg density and location, or dissected and washed to determine larval distribution. Experiments were conducted in the greenhouse with a susceptible population and field with a NST-resistant population. Eggs of both populations were recovered predominantly in cotyledons. Larvae were more uniformly distributed on seedlings. On NST seedlings, oviposition by the susceptible population was reduced and preference shifted to true leaves. NSTs did not alter egg placement by the resistant population. These findings suggest that injury to cotton seedlings is primarily caused by F. fusca emerging on the cotyledons, and then moving to developing leaves. The oviposition shift in NST plants correlates with how systemic NSTs have been reported to concentrate in cotyledons. This can better inform management tactics in cotton, such as well-timed foliar sprays, which, given the current resistance issue, are needed to maintain effective thrips management. [ABSTRACT FROM AUTHOR]

BACKGROUND: Reports of neonicotinoid seed treatment (NST) failure against Frankliniella fusca in the mid‐south and southeastern USA led to the discovery of widespread resistance in these insect populations. Previous studies of NSTs in other crops have shown the concentration of the insecticide to change over time, which could reduce its efficacy. To understand this temporal effect in cotton with F. fusca, our study examined how plant age alters the effects of NSTs (imidacloprid, imidacloprid + thiodicarb and thiamethoxam) by examining larval establishment at multiple seedling ages during the period of cotton seedling susceptibility to this insect. Additionally, we used F. fusca populations with differing neonicotinoid sensitivity levels to understand how resistance impacts this changing efficacy. RESULTS: Greenhouse studies showed that larval numbers were significantly greater on older NST‐grown cotton seedlings. The population with elevated neonicotinoid resistance had a more rapid increase in larval number on thiamethoxam‐treated plants over time. CONCLUSION: NSTs reduce the number of F. fusca larvae on younger seedlings, but this effect declines as seedlings age. The duration of efficacy is shorter against neonicotinoid‐resistant populations. Neonicotinoid resistance in cotton‐infesting F. fusca populations may be accelerated by this time‐dependent decrease in efficacy, which likely encourages low‐dose exposure to these insecticides. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

Simple Summary: Tarnished plant bugs (Hemiptera: Miridae) are an important agricultural pest in cotton across the United States. Tarnished plant bugs reduce cotton yields and lower lint and seed quality by feeding on reproductive structures. Effective management of this pest requires timely insecticidal control when populations reach established economic thresholds. Reliable determination of the economic threshold in cotton depends on effective scouting. To evaluate the efficacy of current tarnished plant bug scouting strategies, we surveyed 120 commercial cotton fields across the southeastern USA to quantify (1) variation in tarnished plant bug populations across the production region, (2) evaluate current sampling plans for economic threshold determinations, and (3) examine landscape-scale risk factors associated with tarnished plant bug infestations in cotton. We observed the greatest variability in tarnished plant bug density at the field scale followed by within-field variation, emphasizing the importance of scouting individual fields. Additionally, we determined the sampling size needed for accurate threshold estimates for sweep net (8 sample units of 100 sweeps/sample) and drop cloth sampling (23 sampling units of 1.5 row-m/sample). Furthermore, tarnished plant bugs densities were positively related to the proportion of agriculture and double-crop winter wheat and soybeans and negatively related to contiguous cotton. Tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae), is an economically damaging pest in cotton production systems across the southern United States. We systematically scouted 120 commercial cotton fields across five southeastern states during susceptible growth stages in 2019 and 2020 to investigate sampling optimization and the effect of interface crop and landscape composition on L. lineolaris abundance. Variance component analysis determined field and within-field spatial scales, compared with agricultural district and state, accounted for more variation in L. lineolaris density using sweep net and drop cloth sampling. This result highlights the importance of field-level scouting efforts. Using within-field samples, a fixed-precision sampling plan determined 8 and 23 sampling units were needed to determine L. lineolaris population estimates with 0.25 precision for sweep net (100 sweeps per unit) and drop cloth (1.5 row-m per unit) sampling, respectively. A spatial Bayesian hierarchical model was developed to determine local landscape (<0.5 km from field edges) effects on L. lineolaris in cotton. The proportion of agricultural area and double-crop wheat and soybeans were positively associated with L. lineolaris density, and fields with more contiguous cotton areas negatively predicted L. lineolaris populations. These results will improve L. lineolaris monitoring programs and treatment management decisions in southeastern USA cotton. [ABSTRACT FROM AUTHOR]

The timing and location of Lygus lineolaris (Palisot de Beauvois) dispersal into cotton is important to accurate and effective scouting and management. In the spring, L. lineolaris populations develop on non-crop weeds surrounding cotton fields. As weeds senesce, L. lineolaris migrate into susceptible cotton at the squaring stage. Given this predictable temporal colonization pattern, scouting efforts to inform insecticide interventions may be improved with a spatiotemporally targeted sampling recommendation. Using a geospatial approach, we tracked L. lineolaris populations at 352 unique sites along transects located in commercial North Carolina cotton fields over two consecutive years. Standardized sweep samples of L. lineolaris adults and nymphs were taken at each site. To relate the abundance of L. lineolaris to the spatial structure of cotton fields, the distance of the sample from the field edge and the edge-to-area ratio of each field were analyzed using GIS. All counts were related to accumulated degree days at each sample time to document seasonal progression of L. lineolaris abundance and temporal host utilization (i.e., weeds vs. cotton). Counts were also related to spatially structured scouting recommendations used in North Carolina. Nymph counts were significantly affected by accumulated degree days and distance from field edge. Higher adult counts were found in fragmented fields with greater edge-to-area ratios. Our results show that L. lineolaris nymphs were more spatiotemporally variable than adults, thereby being more likely to affect scouting accuracy when using sweep samples alone. We found that samples closer to the field edge likely increase the probability of being over the North Carolina L. lineolaris threshold. • L. lineolaris nymphs exhibit greater spatiotemporal variation than adults. • L. lineolaris nymphs are found in higher numbers near the field periphery. • L. lineolaris nymph numbers correlate positively with degree-day accumulation. • Fields with a higher perimeter-to-area ratio may be at higher risk of L. lineolaris. • Spatially structured scouting may stabilize variance associated with field edges. [ABSTRACT FROM AUTHOR]

• Damaging infestations of Lygus lineolaris in Virginia cotton relate to biotic and abiotic factors. • Higher minimum temperatures are associated with increased L. lineolaris infestations. • Crop production area and forest disturbance drive L. lineolaris infestations detected in cotton. Lygus lineolaris populations have become increasingly problematic in Virginia cotton since 2013. Although production practices have changed, changes in landscape composition and climatic conditions are also anecdotally associated with increasing populations. To better understand the recent increase in L. lineolaris infestations in Virginia cotton, 56 commercial cotton fields were sampled weekly in 2017 and 2018 for a nine-week period during the growing season. Insect density was measured using sweep net and black drop cloth sampling, targeting adult and nymphal populations, respectively. Geospatial crop production and forest disturbance data were used to measure the composition and management history of landscapes adjacent to sample fields. We also used spatial climate data sets to document the relationship between increasing L. lineolaris and temperature variation. We investigated the significance of landscape composition and climatic effects increasing L. lineolaris infestation intensity using a regression modeling approach. We found the best overall predictor of L. lineolaris abundance was higher annual minimum temperatures. Several crop components in the landscape were significant, specifically corn and double-crop winter wheat and soybeans, but these habitat patches did not explain high levels of variability. Results of this study suggest that increasing minimum temperatures will favor L. lineolaris and may translate into elevated infestation intensity and increasing dependence on insecticide inputs to manage this problematic pest of cotton. Results of this study will be important to describe short- and long-term factors driving L. lineolaris infestation risk in cotton agroecosystems. [ABSTRACT FROM AUTHOR]