Olax zeylanica: AN ENVIRONMENTALLY SAFE BIO-PESTICIDE FOR THE CONTROLOF THE MAIZE WEEVIL SITOPHILUS ZEAMAIS MOTS. (CURCULIONIDAE)

Abstract

Leaf powders of Ocimum graticimum, Morinda citrifolia, Aegle marmelos, Annona squamosa, Annonareticulata, Olax zeylanica and Ricinus communis were screened for their insecticidal activity underlaboratory conditions (30±1 ºC and 84 - 86% RH) against Sitophilus zeamais. The powders at the rate of15g/50g of maize grains were tested and adult mortality was recorded after 24 hours. O. zeylanica washighly effective against S. zeamais eliciting 100% mortality. Mortality for other six plants was significantlylower ranging from 5.28 to 21.24%. O. zeylanica was tested at five dose rates (1.0, 2.5, 5.0, 7.5, 10.0g) andmortality of adult weevils was recorded after 6, 12 and 24 hours. Mortality of weevils increased with theincrease of the dose as well as the exposure time. Also, weevil mortality was 100% at the dose of 10g justafter 12 hours. Results of this study indicated that leaf powder of O. zeylanica was extremely toxic to S.zeamaize weevils. LD50 and LD99 values after 6,12and 24 hours of exposure were 5.84, 2.47, 1.84g and38.55, 8.33 and 6.51g respectively. The present study revealed that Olax zeylanica has high potential as abio-pesticide which can compete effectively with hazardous insecticides in managing S. zeamaisinfestations.

Keywords: Olax zeylanica, Sitophilus zeamais, Insecticidal activity