In a two-part study conducted in 2005 and 2006, feeding injury to cotton by the western tarnished plant bug, Lygus hesperus Knight, was examined in New Mexico. Part one of this study evaluated feeding by different densities (0, 1, 2, 3, 4, 6, 8, and 10) of L. hesperus nymphs (4th and 5th instar) and adults on whole caged plants. Bugs were allowed to feed for one week before removal. At harvest, plants were mapped and injury ratings were taken to determine impact of the bugs on the cotton crop. Part two of this study evaluated the impact of feeding on individual squares and bolls of known ages of lygus. One bug of each stadia (4th instar, 5th instar, and adult) fed on an individual square or boll for 48 hrs to determine the impacts of this pest. One cohort of squares and bolls was removed after one week to evaluated external and internal evidence of feeding. The other cohort was allowed to develop to maturity to evaluate impacts of feeding on yield.

Whole plant injury in 2005 showed no significant difference between lygus densities. Insect stadia did produce significant differences with 5th instar lygus causing more injury than 4th instar and adults. For the second feeding experiment conducted during 2005, no external feeding lesions were observed for any cotton squares exposed to lygus. Internal injury was significantly greater for 5th instars than adults. External feeding lesions were observed on bolls exposed to all three bug stadia. The greatest number of lesions was produced by 4th instars in young bolls and 5th instars in older bolls. Inner carpel wall injury or “warts” and lint injury were produced by all three age classes of lygus, with 5th instars producing the greatest amount of damage.

Experiments for 2006 are still in progress.