Sensitivities to chill durations and co-chill temperatures regulating eclosion responses differ between Rhagoletis zephyria (Diptera: Tephritidae) and its Braconid parasitoids (Hymenoptera: Braconidae)

Authors: Yee, Wee; GOUGHNOUR, ROBERT - Washington State University; FORBES, ANDREW - University Of Iowa; MILNES, JOSHUA - Washington Department Of Agriculture; FEDER, JEFFERY - University Of Notre Dame

Submitted to: Environmental Entomology
Publication Type: Database / Dataset
Publication Acceptance Date: 1/15/2022
Publication Date: N/A
Citation: N/A

Interpretive Summary: Fruit flies are pests of tree fruit and other fruit that are attacked by natural enemies that could regulate fly populations. Climate change and warming trends could upset the timing of life history events of flies and their wasp parasites, but their possible impacts remain unknown. Personnel at the USDA-ARS Temperate Tree Fruit & Vegetable Research Unit in Wapato, WA, Washington State University, University of Iowa, Washington State Department of Agriculture, and the University of Notre Dame, IN determined the effects of simulated short and long winter lengths on when flies and wasps emerged in the summer under laboratory conditions. Results suggest that the sensitivity of flies to winter cold length as measured by emergence timing is greater than that of wasps, while the sensitivity of wasps to warm summer conditions is greater than that of flies. Our results are important in that they suggest global warming could have potentially significant evolutionary and biocontrol consequences for fruit flies

Technical Abstract: Eclosion timing of temperate insects and their parasitoids are selected for by seasonal temperatures. In western North America, the fruit fly Rhagoletis zephyria Snow (Diptera: Tephritidae) is parasitized by the hymenopterous wasps Utetes lectoides Gahan, an egg parasite, and Opius downesi (Gahan), a larval parasite (both Braconidae). Eclosion of wasps should be timed with the presence of susceptible fly stages. However, previous work has shown that when unchilled inside fly puparia, U. lectoides ecloses while flies do not. Based in part on this finding, we tested the hypotheses that chill durations and no-chill temperatures both differentially regulate eclosion times of R. zephyria and its parasitic wasps. When fly puparia were chilled at ~3ºC for 130–180 d, U. lectoides and O. downesi always eclosed on average later than flies. However, after 180-d chill, flies eclosed on average earlier than after 130- and 150-d chill, while mean eclosion times of both wasps were unaffected by chill duration. When fly puparia were exposed to 20–22ºC (no chill), U. lectoides eclosed before flies, with 88.9% of U. lectoides versus only 0.61% of flies eclosing. Taken together, findings show that the sensitivity of flies to chill duration is greater than that of wasps, while the sensitivity of wasps to no-chill temperatures is greater than that of flies. Our results suggest that shorter winters and longer summers due to climate change could alter eclosion responses of both wasps and flies, but at different stages of their seasonal development, with potentially significant evolutionary consequences