EFFICACY OF BOTANICALS AND SYNTHETIC INSECTICIDES AGAINST MANGO LEAF CUTTING WEEVIL, DEPORAUS MARGINATUS PASCOE

Abstract

The experiment was conducted to study the comparative efficacy of botanicals and synthetic insecticides against mango leaf cutting weevil, a major and destructive pest of mango orchards worldwide, in the laboratory and the mango orchard of the department of Entomology, HSTU and BRAC nursery, Dinajpur during March to August, 2017. Methanol solvent was used to prepare four plant extracts namely eucalyptus, mahagoni, tobacco, neem at three (7.50, 5.00, 2.50 %) concentrations and four insecticides like Nitro 505 EC, Ripcord 10 EC, Fighter 2.5 EC, Belt 24 WG were used in this study. Tobacco plant extracts showed the highest average percentage mortality (24.79 %) among the four botanicals and eucalyptus plant extracts showed the lowest mortality effect (18.75 %) against the adult of Deporaus marginatus. On the basis of insect mortality and LD50 values the order of the toxicity the four botanicals were tobacco> neem>mahagony>eucalyptus. On the other hand, Nitro 505 EC showed the highest mortality (48.75 %) while Belt 24 WG was not effective against D. marginatus in laboratory conditions. The lowest LD50 value of tobacco plant extract also indicated the highest effective against the adult of D. marginatus. However, in field condition, the neem plant extract proveded the lowest leaf infestation (5.127 %) and highest inhibition of leaf infestation (94.46 %) whereas the highest leaf infestation was found in untreated control treatment (92.59 %). The lowest LD50 values, the lowest leaf infestation (11.11 %) and the highest inhabition infestation (88.00 %) indicated that Nitro 505 EC was highly effective against the adult D. marginatus in the laboratory as well as in the field conditions. The order of toxicity of four insecticides against the adult mango leaf cutting weevil were found as Nitro 505 EC>Ripcord 10 EC>Fighter 2.5 EC>Belt 24 WG. Mortality percentage was also found directly proportional to the hour after treatment in both the botanicals and synthetic insecticides applied in the laboratory and field conditions against the adults of D. marginatus.