Boll injury caused by leaffooted bug in late-season cotton

Abstract

Leaffooted bug, Leptoglossus phyllopus (L.) (Hemiptera: Coreidae), has been observed on late-season cotton in south Texas and elsewhere in USA. Field-collected leaffooted bugs were caged on cotton in 2013 and 2014 to characterize symptoms and distribution of boll injury within the cotton plant and within the context of the insect's late-season occurrence (about 5 nodes above white flower). Boll injury and symptoms of cotton boll rot on cotton plants infested with leaffooted bug were similar to those caused by stink bugs and plant bugs. In 2013, there was more boll injury to younger bolls (on average) in reproductive middle branches 6 to 10 (1.28 ± 0.25 boll injury, based on a 0 to 4 scale) than on the relatively older bolls in lower branches 1 to 5 (0.50 ± 0.13), when infesting cotton with one leaffooted bug per plant. Cotton boll rot generally followed the same pattern: higher frequency of boll rot symptoms on bolls in the middle branches (29.4% ± 8.0) than in lower branches (9.2% ± 2.1). In 2014 under severe water-stress conditions, the amount of boll injury and cotton boll rot was marginally lower, and significant differences were not detected between middle and lower branches. When yield was measured in 2013, there were no differences detected between infested and uninfested plants despite substantial boll injury and cotton boll rot. Overall, boll injury and cotton boll rot data supported leaffooted bug as a damaging cotton insect, although yield loss was not detected experimentally late-season which coincided when leaffooted bug has been observed in production fields. We propose that risk to yield is low when leaffooted bug movement to cotton is detected late-season, while risk to yield may increase if leaffooted bugs move to cotton earlier when bolls are younger. Further study is warranted to evaluate degree of risk across cotton boll age, development, and water stress.