Insecticidal activity of leaves of ruta graveolens against the Maize Weevil, Sitophilus zeamais (Motsch.): A green approach for storage pest management (FB1016)

Abstract

Attached

The noticeable propensity towards a 'trek back to nature' has become evident over the past decade in the field of synthetic insecticides resulting out of sheer necessity in replacing these highly toxic chemicals w ith new er and greener strategies as stored grain protectants in the postharvest insect pest m anagem ent programs. In this context, th e potential of leaf pow der of Ruta graveolens (Aruda) was investigated under laboratory conditions fo r its ability to protect stored maize from the attack of Sitophilus zeamais. Efficacy of R. graveolens was determ ined by exposing tw enty one w eek old S. zeamais adults to leaf powders, incorporated into 30 g each of un-infested maize grains at th e doses of 1.0, 3.0, 5.0, 7.0 and 10.0 g. Adult m ortality in both contact and vapor forms was assessed using cup-bioassays and m ortality rates at 3 hour intervals up to 24 hours of post treatm en t w ere recorded. 100% weevil m ortality was observed at doses of 7.0 and 10.0 g within 24 hours of exposure in contact toxicity test, whereas only 68.00 ± 3.54 % and 76.00 ± 4.18 % w ere recorded respectively in fum igation toxicity test after 24 hours. M oreover, th e LD50 values obtained after 24 hours w ere 1.79g and 5.52g for contact and fum igation toxicity tests respectively, indicating th at the contact effect of the leaf powder on weevils is much higher than the fum igation effect. In conclusion, the leaf powders of R. graveolens could be considered as a highly probable candidate in the developm ent of bioinsecticides as safer and economic alternatives to synthetic insecticides to suppress S. zeamais populations.