EVALUATION OF SUSCEPTIBILITY IN DIFFERENT BITTER GOURD VARIETIES TO CUCURBIT FRUIT FLY (BACTROCERA CUCURBITAE COQ.) (DIPTERA: TEPHRITIDAE)

Abstract

An investigation was conducted to study the susceptibility of different bitter gourd varieties viz. tia, heeradill, bulbuli, masrangha, goghkorolla, poran, green queen and sonamukhi to cucurbit fruit fly, Bactrocera cucurbitae (Coq.) based on biophysical fruit traits conducted both in the field and laboratory conditions during the period of February to July 2014. The percent fruit-infestation and larval density were significantly varied among the bitter gourd varieties. The larval density had a significant positive correlation with percent fruit infestation. Biophysical fruit traits like fruit length, fruit diameter, number of longitudinal ribs and small ridges were the lowest in resistant and the highest in susceptible varieties which showed a significant positive correlation with the percent fruit infestation. Additionally the height of longitudinal ribs, depth of small ridges, pericarp thickness and fruit toughness were the highest in resistant and the lowest in susceptible varieties. These parameters showed negative correlation with the percent fruit infestation. It is evident from the results that goghkorolla (19.39 %) categorized as resistant whereas masrangha (41.91 %), tia (46.09 %) and sonamukhi (50.00 %) categorized as moderately resistant varieties. Heeradil (58.89%), green queen (59.05 %), poran (59.44 %) and bulbuli (69.06 %) categorized as susceptible varieties at early fruiting stage. Contrarily, at mid fruiting stage all varieties were susceptible to fruit fly except sonamukhi (46.69 %). Meanwhile, in late fruiting stage all tested varieties showed susceptibility to cucurbit fruit fly. The weight reduction in three different fruiting stages for all bitter gourd varieties was found to be differed and the highest weight reduction obtained from bulbuli and the lowest was the variety of sonamukhi. Among the tested bitter gourd varieties the order of infestation intensity was found as green queen > bulbuli > poran > tia > goghkorolla > heeradil > masrangha > sonamukhi at all three fruiting stages.