Resource Competition Between Melon Fly, Zeugodacus cucurbitae and Oriental Fruit Fly, Bactrocera dorsalis.

The melon fly, Zeugodacus cucurbitae, and the oriental fruit fly, Bactrocera dorsalis, are economically important tephritid pests whose sympatric distribution and overlapping host ranges precipitate intense interspecific competitive interactions. To explore the interspecific competition during larval development between these two species, we conducted a comparative study under controlled laboratory conditions. Larvae were evaluated on five host fruits-pumpkin (Cucurbita moschata), cucumber (Cucumis sativus), winter melon (Benincasa hispida), bitter gourd (Momordica charantia), and guava (Psidium guajava)-across six larval density gradients (4.0, 1.33, 0.8, 0.57, 0.44, and 0.36 larvae g-1 of host tissue). In mixed-species treatments, Z. cucurbitae exhibited significantly higher survival rates and greater adult dry weights than B. dorsalis on all cucurbit hosts except guava, indicating a consistent competitive advantage. Under high-density conditions, mixed-species treatments displayed stronger competitive effects than single-species treatments. Survival rate and adult dry weight of both species were significantly affected by the interactive effects of host plant species and larval density, with these factors jointly determining competitive outcomes. These findings improve our understanding of interspecific competition in tephritid fruit flies and provide a scientific basis for developing more effective management strategies for these economically important pests.