Effects of insect growth regulators with juvenile hormone activity againstCallosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Abstract

Five insect growth regulators, CGA-29170, CGA-45128, MV-678, RO-20458, and fenoxycarb, that exhibit juvenile hormone activity were evaluated for biological and residual activity against the southern cowpea weevil,Callosobruchus maculatus (F.). The compounds were mixed with cowpea seeds at concentrations of 10, 25, 50, and 100 mg/kg, and the residual activity was evaluated at 2-week to 9-months posttreatment intervals. Most JHA-treatments showed high initial activity at the 2-week interval resulting in a significantly lower oviposition rate and showing a short residual life in this respect. CGA-45128, however, at all concentrations tested did not significantly affect oviposition at 2-week to 4-month posttreatment intervals, where was more active and caused high depression in oviposition at 6-month interval. The juvenoids had an inductive effect on the percent egg hatch at various intervals, especially CGA-29170 and CGA-45128 treatments extinding over a period of 9 months. At the lower concentration of 10mg/kg, CGA-45128 was highly effective as F1-progeny suppressant ofC. maculatus at 2-week posttreatment interval extending over 9 months. MV-678, CGA-29170, and fenoxycarb applied at 50, 50, and 25 mg/kg, respectively, showed similar activity, however, the residual activity of the latter decreased after 4 months. RO-20458, however, showed high initial activity at these concentrations. Adult emergence in all treatments was significantly suppressed, where did not exceed 29.5% at the lower concentrations of 10 and/or 25 mg/kg at 9-month posttreatment interval.