MSc

A study was carried out at College of Agriculture, Vellayani during 2010-2011 with the objectives of documenting shoot feeders of mango, assessing the intensity of damage and identifying effective pesticides for their management.

Survey conducted in three taluks of Thiruvananthapuram district revealed the occurrence of eighteen shoot and leaf feeders (nine leaf eating caterpillars, four leaf eating beetles, three sucking pests and two midges) on mango. Among the leaf eating caterpillars, two lycaenids, Rothinda amor and Arhopala sp. are new reports from Kerala. The leaf cutting weevil, Deporaus marginatus was found to be the major leaf feeder of mango with a damage intensity of more than 50 per cent under field condition.

Biology of the weevil was worked out in the laboratory and the egg, larval and pupal periods were 2.5, 6.5 and 13.5 days, respectively. In a single leaf, 1 to 19 eggs were observed and the fecundity of the weevil was 74 to 85 eggs. Based on the feeding as well as the oviposition behaviour of the adults, third to eleventh day of bud bursting was found to be the critical stage of susceptiblilty.

The reaction of twenty one mango varieties against leaf cutting weevil in the flushing season of the plants were observed. All the varieties were found susceptible to weevil infestation with the minimum leaf feeding damage (scraping on leaves) of 56.00 per cent in Jehangir and 83.33 per cent (maximum damage) in Malgoa. Leaf cutting damage was ranging from 16.64 per cent in Kalapadi to 29.17 per cent in Prior and Banganapalli.

Laboratory evaluation of neem seed kernel extract 5%, annona seed extract 5%, neem oil 2%, neem oil garlic emulsion 2%, Econeem 1% revealed that annona seed extract 5% was the most effective with lowest leaf feeding (25.81 per cent) and leaf cutting (34.38 per cent) damage. The mortality of adult and grubs were 43.48 and 83.35 per cent, respectively.

Application of imidacloprid 0.003%, deltamethrin + triazophos 0.05%, triazophos 0.05%, lambdacyhalothrin 0.005% and dimethoate 0.05% on flushes of mango in the laboratory resulted in 90 per cent mortality of both adults and grubs with lambdacyhalothrin 0.005%.

In order to fix the spray schedule, persistence of insecticides were tested and lambdacyhalothrin 0.005% recorded a mortality of 70. 06 per cent on ninth day of treatment.

Field experiment with lambdacyhalothrin 0.005%, deltamethrin+ triazophos 0.05%, dimethoate 0.05%, and annona seed extract 5% indicated the superiority of lambdacyhalothrin 0.005% against leaf cutting weevil. No leaf cutting damage was seen nine days after treatment whereas the leaf feeding damage was 6.71 per cent.

Based on the results the infestation of mango leaf cutting weevil can be managed effectively by applying lambdacyhalothrin 0.005% on the second day of bud bursting and the chemical could give protection to the new flushes during the vulnerable stage of the plant.