A Survey for Potential Biocontrol Agents of Bactrocera cucurbitae (Diptera: Tephritidae) in Thailand

Abstract

Limited investigations on parasitoids of the melon fly, Bactrocera cucurbitae (Coquillett), infesting five species of Cucurbitaceae and seven species of Solanaceae were conducted in Thailand to determine natural occurrence of biological control agents. Fruit samples were collected during January-February 1996, and tephritid puparia were imported into the State of Hawaii Quarantine Facility for fly and parasitoid emergence. Cucumis sativus L., Luffa acutangula (L.), and Momordica charantia L. were commonly infested by B. cucurbitae. Bactrocera tau (Walker) was dominant only in L. acutangula. Infestation of ripe, cultivated fruit of M. charantia was 72.3 B. cucurbitae/kg fruit and parasitoids were pre-dominantly Psyttalia fletcheri (Silvestri) (Hymenoptera: Braconidae), with parasitization rates up to 12.4%. Bactrocera cucurbitae infesting M. charantia in northern Thailand yielded an unidentified Aceratoneuromyia species, (Hymenoptera: Eulophidae). Unlike other eulophids that attack B. cucurbitae, which require the presence of P. fletcheri in the same puparium to suppress host immunity, this parasitoid was able to develop alone. Average fecundity was 135 offspring/ female and mean parasitoids /host puparium was 21.1. It was also developed in the laboratory on the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), with an average life span of 23 d in both host species. Six species of solanaceous fruit were mainly infested by Bactrocera latifrons (Hendel), with infestation rates ranging from 4 to 17 flies/kg fruit. Psyttalia fletcheri and unidentified opiine, Bitomus species, eclosed from B. latifrons infested bird chili, Capsicum frustescens L. Only Lycopersicon esculentum Mill. produced B. cucurbitae, lightly parasitized by P. fletcheri.