LARVICIDAL AND INSECTICIDAL EFFECTS OF DIFFERENT EXTRACTS OF MALLOTUS REPANDUS (WILLD.) MUELL.- ARG. LEAF AND STEM AGAINST CULEX QUINQUEFASCIATUS SAY (DIPTERA: CULICIDAE) AND SITOPHILUS ORYZAE LINN. (COLEOPTERA: CURCULIONIDAE)

Md. Rakib Hasan, Nizam Uddin*, Md. Mahadi Hasan, Md. Monir Hossain, Mohammad Mostafa Kamal, Kaniz Fatema, H. M. Lutfor Rahman Mazumder, Kabirul Bashar, Md. Sohel Rana

This study was designed to evaluate larvicidal bioassay of different extracts of Mallotus repandus against Culex quinquefasciatus and insecticidal bioassay against Sitophilus oryzae in the laboratory. In larvicidal bioassay, methanol extract of leaf, petroleum ether extract of leaf and methanol extract of stem showed good LC₅₀ values (median lethal time) found in three consecutive days (24, 48 and 72 hours). Methanol extract of leaf showed the highest larvicidal activity in each specific time interval. Moreover, the extract also exhibited dose dependent lethal time effect (LT₅₀). In insecticidal bioassay, among all extracts ethyl acetate extract of stem showed the highest insecticidal activity after 24 and 48 hours while petroleum ether extract of leaf exhibited the highest insecticidal activity in 72 hours. Ethyl acetate extract of stem also showed dose dependent LT₅₀. Highly significant (P < 0.0001) relationship between different hours and LC₅₀ values were found in both bioassays. These findings suggest that the extracts have potential toxicity against both insects.