Evaluation of bait application technique for the management of fruit flies infesting cucurbits

Abstract

A survey conducted in Kalliyoor and Nedinjil areas and Instructional farm, Vellayani for the assessment of pest incidence in the field revealed that among the five cucurbits viz., snakegourd, bittergourd, pumpkin, cucumber and coccinia, bittergourd had the maximum percentage incidence and coccinia the minimum. Two spiders viz., Oxyopes shweta and Oxyopes sp. and a larval pupal parasite of fruit flies viz., Opius sp. were observed in the field. From the infested fruits of these cucurbits the maximum number of flies emerged from snakegourd and the minimum from coccinia. B. cucurbitae was the only species that emerged from these infested fruits. The survey conducted in Kalliyoor and Nedinjil areas for documenting farmers’ practices showed that majority of the vegetable growing farmers cultivated cucurbits. The farmers were not following Package of Practices recommendations for spacing and fertilizer and pesticide dosages. All the farmers adopted the use of fruit fly traps, especially Palayankodan + carbofuran trap. In the screening experiment in the field, Rasakadali + jaggery + water + carbofuran, Palayankodan + boiled jaggery + water + carbofuran, Palayankodan + jaggery + water + carbofuran and Palayankodan + carbofuran were found to be significantly superior food baits with respect to total fly catch and duration of effective trap catch. In the cage experiment for selecting two superior baits out of the four baits selected from the field screening trial, Rasakadali + jaggery + water + carbofuran and Palayankodan + boiled jaggery + water + carbofuran were found significantly superior. Heating jaggery to 80oC increased the duration of effective trap catch and keeping quality of food baits. Plastic bottles of 350ml capacity provided with windows of size 6cm x 3cm was found to be the most efficient bait dispenser. In the field experiment for standardization of spacing Rasakadali + jaggery + water + carbofuran at 3.5m x 3.5m had the maximum fly catch, compared to all the other treatments. However there was no significant difference in fly catch when the same food bait was used at different spacing. The significantly lower percentage of incidence was noted when Rasakadali + jaggery + water + carbofuran was used at 2.5m x 2.5m and 3m x 3m and Palayankodan + boiled jaggery + water + carbofuran at 2.5m x 2.5m. The yield was maximum when Rasakadali + jaggery + water + carbofuran was used at 2.5m x 2.5m. The population of foliage pests in the snakegourd field was maximum during peak vegetative stage. The peak population of spiders did not coincide with peak fruit fly population. But the population of Opius sp increased with the population of fruit flies. In correlation with weather parameters it was found that female and total fruit fly population had significant negative correlation with morning relative humidity and number of rainy days. The results of the present study clearly revealed that by the adoption of improved Bait Application Technique profitable production of cucurbits without pesticide contamination is possible.