Efficacy of Chlorpyrifos in Soil in ‘Florunner’ Peanut Fields to Lesser Cornstalk Borer (Lepidoptera: Pyralidae)

Abstract

Survival of lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), larvae in soil from conventionally tilled and planted ‘Florunner’ peanut, Arachis hypogaea L., fields treated with chlorpyrifos in Alabama and Florida was evaluated by testing first instars every 2 wk after application. Treatments were an untreated control and granular chlorpyrifos applied at planting, planting plus pegging, pegging, or flowering. Larval survival in soil from treated plots varied with time of application, location, and year. Application of chlorpyrifos at planting was effective in 1986 and 1987 (42 and 102 d in Alabama; 102 and 72 d in Florida). The fewer days of effectiveness in Alabama in 1986 was probably caused by accelerated chlorpyrifos degradation from hot, dry weather during the growing season. Effectiveness of the application at flowering time was at least as great as effectiveness of the application at pegging. This study indicates that application of chlorpyrifos at flowering or pegging would be more effective for lesser cornstalk borer management than an application at planting, and that these applications would provide adequate control of the lessercornstalk borer during pod-fill.