Biological activity of the shrubBoscia senegalensis (PERS.) LAM. ex Poir. (Capparaceae) on stored grain insects

Biological activity of leaves, fruits and extract of the African shrubBoscia 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 inCallosobruchus maculants (F.) adults and significantly reduced both emergence and damage of the F₁ progeny. Acetone fruit extract exhibited a potent fumigant effect onProstephanus truncatus Horn, C.maculatus, andSitotroga cerealella OLIV.; with LT₅₀ values of 3.8, 2.3, and below 1.5 hr, respectively. LC₅₀ determination forB. senegalensis fruits and leaves as well as pure methylisothiocyanate (MITC) onTribolium castaneum HERBST,Sitophilus zeamais MOTSCH. andC. maculatus showed a differential response of the insects to plant parts or MITC. Quantitative dosage ofBoscia active components and LC₅₀ values obtained for the plant tissues, compared to those of pure molecules, indicate that the biological activity ofB. senegalensis is due to the liberation of MITC from a glucosinolate precursor glucocapparin contained inBoscia fruits and leaves.