Composition, Host Range and Host Suitability of Vegetable-Infesting Tephritids on Cucurbits Cultivated in Kenya

Abstract

Damage incidence and interactions between native and invasive vegetable-infesting fruit flies (Diptera: Tephritidae) on high-value crops have rarely been studied, despite their threats to the horticultural industries in Africa and quarantine implications.We established the composition and host range of tephritid flies in the field and carried out comparative host suitability studies of major fruit flies: Dacus bivittatus (Bigot), Dacus ciliatus Loew and Zeugodacus cucurbitae (Coquillet) on watermelon [Citrullus lanatus (Thunb.)], cucumber (Cucumis sativus L.), courgette (Cucurbita pepo L.) and butternut (Cucurbita moschata Duchesne) in the laboratory. Five new host species were recorded. Zeugodacus cucurbitae was the most destructive fruit fly, infesting 17 hosts from five families, followed by D. ciliatus and D. bivittatus. Direct field damage inflicted on immature to mature crops on the plants ranged from 2.1%on eggplant (Solanum melongena L.) to 66.8%on bitter gourd (Momordica charantia L.). The most preferred hosts of Z. cucurbitae were bitter gourd, watermelon and tomato (Solanum lycopersicum L.) (16.2, 13.3 and 12.1 flies/kg fruit, respectively). Mango (Mangifera indica L.) (24.1 flies/kg fruit) and guava (Psidium guajava L.) (14.7 flies/kg fruit) were recorded for the first time as hosts of D. ciliatus. The relative abundance index showed high variation among host species, suggesting a differential use of these hosts by the different fruit fly species. Choice versus no-choice experiments revealed a significant variation in pupal recovery, pupal size, adult emergence, percentage females, adult wing deformity and body size. These results are significant for the decision-making process for effective monitoring and management of fruit fly species on cucurbitaceous vegetable crops.