Infestation of rose (Rosa spp.) by Rhagoletis pomonella (Walsh, 1867) and Rhagoletis basiola (Osten-Sacken, 1877) (Diptera: Tephritidae) across diverse ecosystems in Washington state, U.S.A.

Rugosa rose, Rosa rugosa Thunberg (Rosales: Rosaceae), native to China, was infested by Rhagoletis pomonella (Walsh, 1867) and R. basiola (Osten-Sacken, 1877) in eastern North America in the 1970s. However, R. rugosa has never been identified as a host of either fly in Washington state, U.S.A. In addition, surveys of R. basiola in different roses across diverse ecosystems in drier eastern versus more humid western Washington assessing the fly's tolerance to arid environments have not been conducted. Here, we report six adults of R. pomonella reared from R. rugosa surveyed in 2020, 2021, and 2023 at a site in western Washington. Rose surveys at other sites in eastern and western Washington where R. pomonella is present detected R. basiola in R. rugosa, native R. nutkana Carl Presl and R. woodsii Lindley, and the introduced R. canina Linnaeus. Rhagoletis basiola was found in rose hips across humid coastal forest, dry ponderosa pine, mountain forest, sagebrush, and bunchgrass ecosystems, with infestation levels in R. nutkana higher in eastern than western Washington. From highest to lowest, infestation levels for the different rose species, in general, were R. rugosa > R. nutkana > R. woodsii > R. canina. Findings here suggest (1) R. rugosa is found mostly in western Washington, so it is unlikely to be a threat as a source of flies to commercial apples in eastern Washington; (2) Rhagoletis basiola is better adapted to dry climates than R. pomonella; and (3) the abundance of R. basiola infesting roses in Washington is affected by both regional climate and rose species.