Submitted to: The Canadian Entomologist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/15/2013
Publication Date: 3/20/2013
Citation: Yee, W.L. 2013. Soil moisture and relative humidity effects during post-diapause on emergence of western cherry fruit fly (Diptera: Tephritidae). The Canadian Entomologist. 145:1-10. Interpretive Summary: The western cherry fruit fly damages sweet cherry fruit and is a major quarantine pest of cherries in the western U.S. Determining environmental requirements of the fly is needed to help predict whether it can establish in different regions where cherries are grown. Personnel at the USDA-ARS Yakima Agricultural Research Laboratory in Wapato, WA tested the effects of different soil moistures and air humidity on the ability of fly pupae to survive and emerge as adults. It was found that flies emerged at high levels under a wide range of dry to moist soil and air conditions. This result helps explain the broad distribution of the fly and can be used to assess the risk of it becoming a pest in regions where it is not currently found.
Technical Abstract: Western cherry fruit fly, Rhagoletis indifferens Curran, is a pest of sweet cherry, Prunus avium (L.) L., in western North America that is found in relatively moist and dry habitats. In this study, fly pupae from Kennewick and Roslyn in Washington state, U.S.A., were used to test the hypotheses that emergence of flies (1) from dry and moist soil is similar but that (2) it is greater and occurs earlier at high than low relative humidities. Adult fly emergence from 0–57% saturated loam soil did not differ in Kennewick (64.8–75.1%) and Roslyn (81.7–86.6%) populations. Emergence did not occur from 76% saturated loam soil. In a relative humidity (RH) experiment, emergence of Kennewick flies was highest at 97% RH (76.8%), intermediate at 12–74% RH (66.4–69.6%), and lowest at 3% RH (58.0%). Emergence of Roslyn flies was higher at 97% RH (85.6%) than 3% (69.2%) and 12% RH (74.3%), but it did not differ from that at 33% (76.9%) and 74% RH (79.4%). Flies emerged ~2–3 days earlier at 97% RH than at 3–12% RH. An unnaturally low RH of 3% caused more flies to be deformed than higher RHs. Compared with other Rhagoletis pupae whose responses to soil moisture and RH have been reported in the literature, post-diapausing pupae of R. indifferens appear relatively tolerant of dry and moist environments. This likely contributes to the presence of R. indifferens in a wide range of native and non-native habitats.