ABSTRACT

Field tests were conducted in northeastern Louisiana from 1995-2003 to define boll and yield tolerance to late-season cotton pests. The insect pests included bollworm, fall armyworm, beet armyworm, tarnished plant bug and brown stink bug. Lepidopteran larvae and “bugs” were caged on cotton bolls of various ages to define the period of boll susceptibility to insect injury. Bolls that accumulated 426.5 (17.1 d) HU beyond anthesis before infestation were not injured by first-instar bollworm larvae. Bolls accumulating 350 HU were successfully penetrated by fall armyworm and beet armyworm at unacceptable (≥ 10%) levels. For tarnished plant bugs, seedcotton yields were significantly lower for bolls that had accumulated between 99 to 326.5 HU after anthesis, compared to non-infested bolls. Seedcotton yields were significantly lower for brown stink bug infested bolls compared to that of non-infested bolls through ca. 550 HU beyond anthesis. Insect-simulated defoliation of cotton at 66% and 99% leaf removal resulted in mean seedcotton yield losses of 23.8% and 51.1%, respectively, below that in the non-defoliated plots at 350 HU after anthesis.