Toxicity and repellency activities of the crude methanol extract of duabanga grandiflora (lythraceae) against sitophilus oryzae (Coleoptera: Curculionidae)

Laboratory bioassays were carried out to examine the toxicity and repellency of a crude methanol extract of duabanga grandiflora against adult rice weevil,sitophilus oryzae. toxicity was evaluated using a nochoice test with treated filter paper and rice grains while repellency evaluated using a choice test with treated filter paper. the crude methanol extract was found to possess low toxicity against s. oryzae with maximum mortality of 33% at 32 mg/ml (w/v) 7 days after exposure. toxicity depended on both concentration and duration. the crude methanol extract was also repellent against s. oryzae ranging from 37 and 83% at 5 min to 2 h after exposure and from 60 to 100% at 4 to 24 h after exposure. the exposure period appeared to be the most important factor affecting the repellent effect of crude methanol extract of d. grandiflora (p < 0.05) while the tested concentrations showed no different in repellent activity (p > 0.05). © 2012 zoological society of pakistan.