MSc

A study on “Management of melon fly, Bactrocera cucurbitae Coquillett using local isolates entomopathogenic fungi viz., B.bassiana (ITCC 6063), P.lilacinus (ITCC 6064), A.candidus (ITCC 5428)” was conducted in the Department of Agricultural Entomology, College of Agriculture, Vellayani.These fungi were screened against the pupae and adults of melon fly. The most promising fungus was selected based on its efficacy, mass multiplied for field application, standardized for field dosage and method of application.

Dietary constituents comprising of honey, sucrose, jaggery, sugar and water in combination with yeast were evaluated for the laboratory rearing of melon fly. Bait preparation in 100 ml water containing 20g jaggery and 10g yeast was the best suitable diet for in vitro rearing of melon fly.

The bioassay of the fungi on the pupae and adults was conducted and the most promising fungus was selected. The studies were conducted by soil drenching (pupae) and spraying (adults) using different spore concentrations of the fungi. Based on the percentage mortality and LC50 value, Paecilomyces lilacinus was identified as the most promising fungus for the management of melon fly.

The fungus was mass multiplied on locally available cheaper solid (rice bran, wheat bran, gingelly oil cake, coir pith, neem cake) and liquid substrates (rice bran extract, wheat bran extract, boiled rice water, coconut water and water). Rice bran recorded the maximum spore count of P.lilacinus on 28th day after inoculation. The fungus cultured in rice bran, showed the maximum efficacy in causing pathogenicity on the pupae and adults of melon flies.

In vitro studies were conducted to evaluate the efficacy of the P. lilacinus on adults and pupae of melon flies under cage and trough conditions. Soil drenching with P. lilacinus @ 1.3x109 spores /ml (30 ml per trough) resulted in 92.45% mortality in pupae, five days after inoculation in soil, under trough conditions. Spraying with P. lilacinus @ 2.4x109 spores/ml recorded cent per cent mortality in adults, three days after treatment, under cage conditions.

Food baits containing banana, jaggery and malathion in different combinations were used to document the peak time of activity of melon fly. Bait preparations in water (100 ml) containing 30g banana, 10g jaggery, 0.2 ml malathion and 10g yeast, showed superior performance in the trap catch of melon flies, with the peak during 8-10 a.m.

Field experiment was conducted with the treatments viz., soil drenching (P. lilacinus), spraying (P. lilacinus), soil drenching + spraying (P. lilacinus), 0.2% malathion spray and control. Soil drenching with P. lilacinus at a spore concentration of 1.3x109 spores/ml (170 g P. lilacinus multiplied in rice bran in 17 litres of water per 40 m2) + spraying with P. lilacinus at 2.4x109 spores/ml (20 g P. lilacinus multiplied in rice bran in 2 litres of water per 40 m2) recorded the minimum percentage infestation of melon fly. The same treatment recorded significantly higher yield (16.6 t/ha) and a B: C ratio of 2.92 in bittergourd. Soil drenching with P. lilacinus recorded the maximum number of infected pupae in soil under field conditions. Lower incidence of pumpkin caterpillar was observed in soil drenching + spraying with P. lilacinus.. This treatment supported the maximum incidence of natural enemies under field condition.