Mortality of western cherry fruit fly (Diptera: Tephritidae) eggs and larvae in cherries submerged in hypoxic water

Authors: Yee, Wee; PENCA, J - ANIMAL AND PLANT HEALTH INSPECTION SERVICE (APHIS)

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2023
Publication Date: 12/7/2023
Citation: Yee, W.L., Penca, J. 2023. Mortality of western cherry fruit fly (Diptera: Tephritidae) eggs and larvae in cherries submerged in hypoxic water. Florida Entomologist. 106(4)238-243. https://doi.org/10.1653/024.106.0405.
DOI: https://doi.org/10.1653/024.106.0405

Interpretive Summary: Western cherry fruit fly is a quarantine pest of cherry in western North America. Determining the water tolerance of its maggots in cherries can help us understand fly adaptations to stressful environments and also have practical value for sanitizing orchards. Personnel at the USDA Temperate Tree Fruit & Vegetable Research Laboratory in Wapato, WA and USDA-APHIS in Miami, FL determined the effects of submerging infested cherries in water for 4, 8, and 12 days on kill of fly eggs and maggots in the cherries. It was found that 8- and 12-day water submersions killed 100% of eggs and maggots. Results are important in that they may lead to water submersion of unpicked, infested fruit being a viable orchard sanitation method for managing fruit flies, in cherries and possibly other fruit systems.

Technical Abstract: Determining the tolerance of tephritid fruit flies (Diptera: Tephritidae) to water submersion can help us better understand adaptations of flies to stressful environments and how it could be used practically in orchard sanitation for managing tephritids. Here, we determined the mortality of eggs and larvae of western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), in cherries submerged in hypoxic water for 4, 8, and 12 d. In 2020, 2021, and 2022, infested ripe cherries (mostly Prunus avium L.) were collected from unmanaged trees outside orchards in central Washington State, U.S.A., submerged in water, and then removed from water to monitor for larval emergence. Before submersion, eggs comprised 43.1–62.3% of immature stages in cherries while second or third instars comprised 17.6–26.2%. Treatment waters contained ~4 to <1 ppm dissolved oxygen over the 4- to 12-d tests. The 4-d submersion did not kill all eggs or larvae, whereas 8- and 12-d treatments did. In the 8-d treatment, an estimated 49,016 eggs and larvae were killed with no survivors, for 99.99389% mortality (95% confidence interval) and probit 8.8416, relevant for water submersion of unpicked infested cherries as a post-harvest treatment. The inability of R. indifferens to tolerate hypoxic water beyond 8 d, unlike some tropical tephritids, may a side effect of its evolution in non-riparian habitats. Results show water submersion for disinfesting fruit as a proof of concept that could be utilized in systems where orchard sanitation is the major and most accessible method for fly management.