The Effectiveness of Fruit Bagging and Culling for Risk Mitigation of Fruit Flies Affecting Citrus in China: A Preliminary Report

Several tephritid fruit fly species that are damaging to citrus in China are world-wide quarantine pests. Two field tests were conducted in China to evaluate the effectiveness of fruit bagging (i.e., fruits were grown in bags for at least 1.5 mo until harvest) and culling for risk mitigation of these pests during the fruit harvest season of 2017. The first test was conducted in Pinghe County of Fujian Province. The purpose of this test was to assess the effectiveness of fruit bagging on risk mitigation of fruit flies affecting pomelo, Citrus maxima (Burm. fil.) Osbeck (Rutaceae). External inspection and internal fruit cutting of 3,000 bagged and 3,040 unbagged fruits revealed few oviposition marks and absence of living flies in the bagged fruits, compared to 129 fruit fly-infested fruits containing 634 live larvae and 4 pupae in the unbagged fruits. Later molecular and morphological identification concluded that these larvae and pupae were Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). The second test was conducted in Shimen County of Hunan Province. The purpose of this test was to assess the effectiveness of packing house culling on risk mitigation of fruit flies in Satsuma mandarin, Citrus unshiu (Swingle) Marcov. (Rutaceae). A total of 20,000 fruits were cut (10,000 fruits before culling, and another 10,000 after culling). In the fruits that did not receive the culling treatment, 1 infested fruit with 7 third instar larvae of Bactrocera minax (Enderlein) (Diptera: Tephritidae) and 25 fruits with fruit fly oviposition marks were found. In the fruits that received the culling treatment, fruit flies were absent and 10 fruits with oviposition marks were found. These results suggest that fruit bagging and packinghouse culling could contribute to risk mitigation of fruit flies in citrus in China. This is a preliminary report, with further work necessary to develop a systems approach for risk mitigation of fruit flies in the commodities.