Late Season Beet Armyworm (Lepidoptera: Noctuidae) Infestations on Cotton: Defoliation, Fruit Damage, And Yield Loss

Abstract

Field cage studies were conducted in 1996 and 1997 to measure the effects of late season beet armyworm, Spodoptera exigua (Hübner), infestations (0, 1, 3, and 6 egg masses per 5.1 m row) on defoliation, fruit damage, and yield of cotton. Significantly higher light penetration through the cotton canopy was observed in most infested plots compared with non-infested control plots. A trend for higher numbers of damaged fruiting forms (squares and bolls) with increases in egg mass density was observed. There were no significant differences in the number of damaged fruiting forms among treatments, however, plots infested with 1, 3, or 6 egg masses had 2.3, 2.4, and 3.3-fold more damaged fruiting forms than the control plots. In all infested plots, a significantly higher percentage of shed fruiting forms were damaged compared with the control plots in 1996. In 1997, only plots infested with 6 egg masses had a significantly higher percent of the cumulative fruiting forms damaged compared with the control plots. In both years, there were no significant differences in seed cotton yield among treatments.