impact of three application methods of spinosad in the management of callosobruchus maculatus (fabr.) (coleoptera: bruchidae)

Cowpea beetle, Callosobruchus maculatus (Fabr.) is considered the most important pest of cowpea, Vigna unguiculata (L.) Walp., stored in tropical and sub tropical regions. Laboratory bioassays were carried out in order to evaluate the effectiveness of spinosad (Tracer 24 % SC) by using three application methods, contact, fumigant and repellent toxicity, against the cowpea beetle C. maculates. Regarding to the contact toxicity, when spinosad applicated by thin film residue in petri dishes(9 cm² diameter) its LC50s and LC90s recorded 122.55 and 1285.88 ppm, respectively, comperated with 645.06 and 3884.36 ppm, for grain mixing method after 24 h. The percentage of hatching eggs varied from 40.60 to 71.90 %, while the numbers of emerged adults ranged from 10 to 81 insects, comperated with 299 for control. The reduction of progeny ranged from 70.07 to 100.00 with 250 and 1500 ppm. The Main development period (period of generation) ranged from 38.00 to 60 day comperated with 24 days for control. Application of spinosad as fumigant recorded 224.599 and 1464.980 ppm (50 cm³), for LC50s and LC90s , respectively. The repellent activity of spinosad by two applications methods resulted 100 % percentage repellency for adults at concentrations of 300 and 750 ppm for petri dish and jar techniques, respectively. Spinosad may be a good choice as a potent boinsecticide by thin residue film method against studied stored product insect C. maculatus .