BIOLOGICAL TRAITS AND EFFICACY OF SOME SYNTHETIC PESTICIDES AGAINST MANGO LEAF CUTTING WEEVIL (Deporaus marginatus Pascoe)

Abstract

Mango leaf cutting weevil (Deporaus marginatus Pascoe) is a major and destructive pest of mango causes substantial damage to the foliage and ultimately yield. The development, reproductive biology and management of D. marginatus were investigated on four popular mango varieties namely Langra, Amrapali, Fazli and Ashwina. Biological performance of the insect was studied in the laboratory conditions (25-30°C, RH 80-85% and 13±1:11±1 D: L). The longest immature development period (19.81± 0.17 days) was found in Langra while the shortest (19.30 ± 0.14 days) in Ashwina. The longest longevity was (50.30 ± 1.68) and (70.50 ± 1.02) days for female and male, respectively while reared on Fazli. On the contrary, the shortest longevity of female (39.65 ± 1.33 days) and male (63.40 ± 1.15 days) was observed in Ashwina and Langra, respectively. Life time fecundity was also the highest (1438.20) on Ashwina and the lowest (1100.50) on Langra. The sex ratio (proportion of male) was the maximum (0.45) on Langra and the minimum (0.38) on Fazli. The net reproductive rate (Ro = 876.69), intrinsic rate of natural increase (rm = 0.18), finite rate of increase (λ = 1.19) were maximum and the generation time (T = 38.47) was the minimum when fed on d the Ashwina. An evaluation was also made for assess the effect of four insecticides viz. Nitro 505 EC, Ripcord 10 EC, Fighter 2.5 EC and Belt 24 WG on the D. marginatus. The test was conducted in both the laboratory and field conditions using mango variety Amrapali. Nitro 505 EC showed the highest mortality (58.75%) while the lowest (37.29%) was found in Fighter 2.5 EC in the laboratory conditions. The lowest LD50 value indicated that Nitro 505 EC was highly effective against the adult D. marginatus. No leaf infestation (0%) was found on both Nitro 505 EC and Ripcord 10 EC sprayed tree in the field conditions and the highest leaf infestations (89.4%) were recorded on Belt 24 WG. It is revealed from the results that Langra was less preferable host as compared to others and Nitro 505 EC was most effective to control the D. marginatus in both the laboratory and field conditions.