Cotton Square Damage by the Plant Bug, Lygus hesperus (Hemiptera: Heteroptera: Miridae), and Abscission Rates

Abstract

Numbers of Lygus Hesperus Knight per 50 net sweeps and numbers of abscised and lygus bug damaged squares per cotton plant terminal were counted weekly. Square abscission and square damage showed a high positive correlation with L. hesperus numbers (r = 0.92, n = 7, for week of count and r = 0.69, n = 63, for June through July) and with square age (r = 0.96, n = 20); fruit set on first and second sympodial branch positions showed a high negative correlation with L. Hesperus numbers (r = -0.65, n = 25, for zero to six bugs per 50 sweeps). Comparisons of the proportion of squares damaged by lygus bugs between the terminal 5 nodes, terminal 10 nodes, and all nodes on one to three dates per location indicate that the terminal 5 nodes provide a reliable estimate of L. Hesperus feeding damage to squares. Our calculations indicate that before 1 August each lygus bug collected in the sweep net indicates a potential for 23,400 abscised plus damaged squares per hectare on the day of sample. Boll retention in relation to lygus bug numbers is presented. This information is expected to provide guidance when developing management strategies for L. hesperus on cotton. Square damage and loss can be used to estimate need for pesticide use and for refining the lygus bug: square ratio as an estimator of treatment threshold.