Cucurbit fruit fly is the most destructive pest of bitter gourd throughout the country. The pest attacks other cucurbitaceous vegetables such as bottle gourd, cucumber, tinda, pumpkin, gherkin, etc.
Adult fly punctures the early tender fruit tissues and lays its eggs. The infestation often reaches cent per cent leading to complete loss of the crop. The maggots feed on the contents of fruits and cause premature dropping of fruits.
Infested fruits can be identified by the presence of brown resinous juice which oozes out of the punctures made by the flies. The punctures serve as entry for various bacteria and fungi and as the result of the infection, fruits start rotting, get distorted, malformed and fall prematurely.
The fly breeds throughout the year. Females thrust around 50 eggs as groups into tender fruits. The eggs hatch in 1-9 days and the maggots bore into the pulp forming galleries.
Seven days old pale white mature larvae come out of the rotten fruits and bury themselves about 5cm deep into the soil and pupate. Barrel shaped brown puparium emerge as adult flies in two weeks.
Adult flies are reddish brown in colour. They feed on honey dew and juices of ripe injured fruits.
There are several generations in a year. The population of the pest is low in hot dry conditions and high during rainy season.
— Grow fruit fly tolerant bitter gourd varieties.
— Collect and destroy infested fruits such as fallen, deformed and stunted fruits.
— Frequently rake up or plough the soil to expose pupae to their natural enemies and detrimental weather.
— Grow maize as border crop as the flies have the habit of resting on such tall plants. Maize alone can be sprayed with insecticides.
— Use ribbed gourd as trap crop and apply carbaryl 0.15 per cent or malathion 0.1 per cent on congregating adult flies on the under surface of leaves.
— Apply bait containing 50ml of malathion + 0.5kg of gur/sugar in 50 litre of water and it may be repeated at weekly interval if the attack is serious.
— Use traps citronella oil, eucalyptus oil, vinegar(acetic acid) and lactic acid to trap flies.
(Dr. J. Jayaraj, Professor of Entomology, Agricultural College and Research Institute, Madurai 625 104, email: email@example.com, Phone No. 0452-2422946.)