Effect of Selected Insecticides onLygus hesperus(Heteroptera: Miridae) Oviposition Behavior in Cotton

Abstract

Oviposition behavior of western tarnished plant bug, Lygus hesperus Knight, as affected by residual insecticides, was studied in potted as well as field-grown cotton. In this study, we investigated the spatial distribution and phytotomical preference of Lygus oviposition in presquaring and blooming cotton, as affected by selected insecticides. Flonicamid, acephate, and cypermethrin were applied to cotton at 82, 516, and 114 g (active ingredient)/ha, respectively. At 3 d posttreatment, a gravid female Lygus was caged on the plants. After 4 d, caged plants were harvested and eggs were counted by whole plant dissection. Results indicated significantly greater egg deposition in untreated controls than treated plants in both potted and field-grown cotton. For untreated plants, Lygus preferred to oviposit on the pulvinus and leaf petiole, where 76 and 85% of eggs were laid in potted and field-grown cotton, respectively. For insecticide-treated plants, no plant structure preference was observed, although fewer eggs were laid. The upper stratum of the plant canopy had significantly more eggs than the lower or middle strata of untreated plants, while more eggs were observed in the middle strata of plants treated with acephate in field-grown cotton. Sublethal effects could not be adequately assessed in the cypermethrin treatment owing to high Lygus mortality.

Accuracy of Lygus hesperus Knight (Hemiptera: Miridae) Egg Counts Improves with Egg Development

“…The range of numbers of total eggs observed in our study easily encompassed estimates of L. hesperus daily oviposition from previous reports (Balachandran et al, 2014;Mueller and Stern, 1973;Strong et al, 1970). In fact, the mean numbers of eggs (± S.E.)…”

“…In most studies of Lygus spp. oviposition, eggs in a wide variety of host plants have been detected by visual observation, often with the aid of a dissecting microscope (Abel et al, 2010;Balachandran et al, 2014;Brent et al, 2011;Conti et al, 2012;Elmore, 1955;Noma and Strickler, 2000;Ugine, 2011Ugine, , 2012. During studies of L. hesperus egg development Spurgeon, 2012, 2013), it was observed that, despite careful examination, the numbers of eggs detected visually in pods of green bean (Phaseolus vulgaris L.) were often lower than the numbers of resultant nymphs (W.R.C.…”