Farm field assessments of fruit flies (Diptera: Tephritidae) in Pakistan: distribution, damage and control

Abstract

The abundance and distribution of fruit flies ( Bactrocera zonata and cucurbitae and Carpomyia vesuviana) in melon, guava, jujube and mango were assessed in farmers’ fields, under different control regimes, in four areas of Pakistan. Larval distribution was not clustered among trees but was highly clustered among fruit. The mean number of larvae per infested fruit was not constant, and was not significantly less variable than the infestation rate. In comparisons of bait application technique (BAT) with farmer controls, in melon, average season-end fruit infestation was 29% in unprotected fields and 5% in those protected by BAT; in guava infestation was 44% in unprotected orchards and 12% in orchards protected by BAT; in jujube, infestation was 16% in unprotected orchards and 4% in those protected by BAT. Fifteen farmer-managed trials found BAT-treated melon fields yielded 37% more than unprotected and farmers reported considerable satisfaction. In mango, soaked-block male annihilation technique (MAT) was compared with farmer practices of no control: average infestation before harvest was 9% in unprotected plots and 0% in those protected. Additional to differences in infestation rate, protected melon fields produced 17% higher yields of all fruit, and protected guava orchards had 20% more fruit on trees, relative to those fallen, suggesting that fly attack stimulated fruit drop, and loss estimates based on percentage infestation of sampled fruit may be underestimates. If these reductions in infestation are extrapolated to loss estimates for Pakistan as a whole, the gross annual saving inferred is 4915 million Pakistan rupees or US$144.6 million.