|Cooper, Rodney - William|
Submitted to: Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/30/2012
Publication Date: N/A
Technical Abstract: Despite the importance of Lygus hesperus as a crop pest in the western United States, key aspects of its feeding behavior and consequent injury to cotton are poorly understood. Previous studies of Lygus stage-dependent injury to cotton produced conflicting results. We sought to clarify these relationships by employing an experimental strategy that integrated observations of feeding behavior and within-plant distribution with traditional assays of plant injury. Video-based assays indicated that prereproductive adults allocated more time to feeding and less time to trivial movement compared with reproductive adults. These observations were consistent with results of greenhouse assays, where prereproductive adults more often resided on vegetative or reproductive buds, and produced higher numbers of injured and abscised squares, compared with reproductive adults. Direct comparisons of feeding injury to intact plants by third and fifth instars, and prereproductive adult females, indicated plants exposed to third instars had more injured squares attached to plants whereas the plants exposed to fifth instars had more abscised squares. These differences were not explained by respective feeding behaviors observed in video assays, but were associated with differences in within-plant distribution corresponding to insect age class. Fifth instars were often observed feeding in plant terminals containing small squares that are highly susceptible to abscission. Third instars were most often found sheltered within the bracteoles of larger squares that could better tolerate Lygus feeding. In contrast, prereproductive adults were less frequently associated with fruiting structures than were either nymphal instar. Our results indicate that age-dependent differences in Lygus injury to cotton can be explained by corresponding differences in behavior. These findings emphasize that variability in studies of plant injury can be minimized by controlling Lygus age class, and suggest the need to include estimates of nymph populations in treatment thresholds.