BIOLOGICAL-ACTIVITY OF THE SHRUB BOSCIA-SENEGALENSIS (PERS) LAM EX-POIR (CAPPARACEAE) ON STORED GRAIN INSECTS

Biological activity of leaves, fruits and extract of the African shrub Boscia senegalensis (PERS.) LAM. ex Poir. was evaluated against five stored-grain insects. When added to cowpeas at 2-4% (w/w), fresh ground fruits and leaves caused 80-100% mortality in Callosobruchus maculatus (F.) adults and significantly reduced both emergence and damage of the F1 progeny. Acetone fruit extract exhibited a potent fumigant effect on Prostephanus truncatus HORN., C maculatus, and Sitotroga cerealella OLIV.: with LT50 values of 3.8, 2.3, and below 1.5 hr, respectively. LC50 determination for B. senegalensis fruits and leaves as well as pure methylisothiocyanate (MITC) on Tribolium castaneum HERBST, Sitophilus zeamais MOTSCH. and C. maculatus showed a differential response of the insects to plant parts or MITC. Quantitative dosage of Boscia active components and LC50 values obtained for the plant tissues, compared to those of pure molecules, indicate that the biological activity of B. senegalensis is due to the liberation of MITC from a glucosinolate precursor glucocapparin contained in Boscia fruits and leaves.