Effectiveness of spinosad on adults of the cowpea beetle, Callosobruchus maculatus(F.) and their control costs

Mohamed M. Azab*; A.A. Darwish *; A.M. Abd El- Lateif **; A.M. Abdel-Aal***

Abstract

Laboratory bioassays were carried out to evaluate the effectiveness of spinosad by using five concentrations (20, 15, 10, 5 and 1 mg/kg) on cowpea seeds against the cowpea beetle, C. maculatus (F.) (Coleoptera: Bruchidae). The results indicated that the adults of cowpea beetle were more susceptible to spinosad at 30ºC (LC50: 0.925 mg/kg, LC90: 28.95 mg/kg) than at 20ºC (LC50: 1.403 mg/kg, LC90: 86.7 mg/kg) after 72 hrs from treatment. The shortest lethal time values (LT50s and LT90s) were obtained at spinosad concentration of 20 mg/kg when the tested insect treated at 30ºC, LT50s and LT90s were 12.68 and 37.95 hrs, respectively, and 16.51 and 65.35 hrs at 20ºC, respectively. Results also showed the greatest reductions in the insect progeny were 100.00 and 99.78% at the highest concentration tested (20 mg/kg) under 20 and 30oC, respectively. Furthermore, control coasts of the tested insect were estimated about 50.5 EL/1000 kg of cowpea seeds. It was concluded that spinosad had considerable toxicity against adults of cowpea beetle and it may be an effective alternative bio-pesticide for control adults of this pest in storage.

Key words

spinosad, bioassays, C. maculatus, toxicity, progeny