Search

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]