Fruit fly species diversity, population dynamics and infestation rate during fruiting season of snake gourd

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A monitoring survey was conducted in snake gourd agro ecosystem during the fruiting season at Gangnapur, West Bengal, India to generate extensive data on fruit fly diversity, population dynamics, infestation rates and evaluate the effect of trapping on fruit fly infestation rates vis-à-vis benefit cost ratio of snake gourd cultivation. Methyl Eugenol and Cue Lure traps were used to assess the fruit fly species diversity. The number of adult male flies trapped was used to calculate fruit fly per trap per day and assess the population dynamics. Bactrocera dorsalis, Zeugodacus cucurbitae and Zeugodacus tau were the predominant fruit fly species during the fruiting season. Maximum species diversity and evenness estimates were registered by Methyl Eugenol traps. Species richness estimates for Cue Lure and Methyl Eugenol traps during the entire experiment are analogous due to the trapping of two different types of fruit fly species. Zeugodacus cucurbitae is the most abundant species in the snake gourd ecosystem and dominated the community of fruit flies throughout the study. Fruit fly per trap per day values indicated that the Gangnapur area is at infestation level, for Zeugodacus cucurbitae and Bactrocera dorsalis, while, for Zeugodacus tau the area is at suppression level. The rate of infestation varied from 6.93 % to 44.09 %. Farmers with traps in their fields reported a benefit cost ratio of 0.73 to 4.63, while the no-trap group reported 0.34 to 1.56. This study at Gangnapur has proven the beneficial effect of trapping on the benefit cost ratio of snake gourd cultivation.