Morphometrics and Management of Chinese Citrus Fly, Bactrocera minax (Enderlein) (Diptera: Tephritidae) in Kathmandu, Nepal

Abstract

The study was performed at the citrus orchard of Chhahari Retreat in Budhanilkantha, Kathmandu, examined the morphological measurements of both pupa and adult of Bactrocera minax, with a study from March to July 2023. The average pupal length of the Chinese citrus fly determined 9.44 ± 0.10 mm, with a corresponding breadth of 4.33 ± 0.09 mm and weight of 0.051 ± 0.002 gm. Notably, the body length of adult female B. minax surpassed that of males, measuring at 13.9 ± 0.20 mm compared to 11.93 ± 0.33 mm for males, while females exhibited broader bodies (3.92 ± 0.06 mm) in contrast to males (3.18 ± 0.05 mm). Furthermore, adult females displayed a wider wingspan (22.21 ± 0.23 mm) relative to adult males (21.36 ± 0.30 mm), along with longer wings (9.22 ± 0.16 mm) compared to males (8.86 ± 0.16 mm). The ovipositor length was 4.62 ± 0.62 mm. The average weight of female adults calculated 0.0228 ± 0.001 gm, whereas male adults exhibited an average weight of 0.0141 ± 0.002 gm. This research emphasizes significant morphological differences between male and female flies. Furthermore, an attempt was made to manage this pest through the implementation of Area-wide Control Program (AWCP), involving the application of a lethal protein bait comprising 25% protein hydrolysate and 0.1% abamectin (Great fruit fly bait), through spot application at weekly intervals from 8th May to 24th July 2023. A notable decline in fruit loss was observed, decreasing to 1.24% from the previously recorded 27.68% during the 2023 harvest season. This substantial reduction in overall fruit loss, amounting to a noteworthy 26.44% decrease in comparison to 2022 (p<0.00), was effectively attained.