POPULATION ECOLOGY Differences in Body Size and Egg Loads of Rhagoletis indifferens (Diptera: Tephritidae) From Introduced and Native Cherries

4 WEE L. YEE,'·2 ROBERT B. GOUGHNOUR,3 AND JEFFREY L. FEDER

Environ. Entomol. 40(6),1353-1362 (2011); DOl, http,lIdx.doi.org/l0.l603/ENlll28 ABSTRACT The western cherry fruit fly, Rhago1etis indifferens Curran, infests introduced, domes­ ticated sweet [Prunus avium (L) L], and tart cherries (Prunus cerasus L) as well as native bitter cherry, Prunus emarginata (Douglas) Eaton. Bitter cherries are smaller than sweet and tart cherries and this could affect various life history traits of flies. The objectives of the current study were to determine 1) if body size·and egg loads of flies infesting sweet, tart, and bitter cherries differ from· one another; and 2) ifany observed body size differences are genetically based or caused by the host fruit environment. Pupae and adults ofboth sexes reared from larval-infested sweet and tart cherries collected in Washington and Montana were larger than those reared from bitter cherries. In addition, flies ofboth sexes caught on traps in sweet and tart cherry trees were larger than those caught in bitter cherry trees and females trapped from sweet and tart cherry trees had 54.0-98.8% more eggs. The progeny of flies from naturally-infested sweet and bitter cherries reared for one generation in the laboratoryon sweet cherrydid notdiffer in size. The same also was truefor progeny ofsweet and bitter cherry flies reared in the field on bitter cherry. The results suggest that the larger body sizes of flies from sweet and tart cherries than bitter cherries in the field are caused by host fruit and not genetic factors.

KEY WORDS Western cherry fruit fly, Prunus avium, Prunus emarginata, head width, wing length

The western cherry fruit fly, Rhago1etis indifferens indifferens attacks both subspecies of bitter cherry Curran. infests introduced, domesticated, sweet in Washington (Yee 2008, Yee and Goughnour (Prunus avium (L.) L.] and tart cherries (Pronus 2008), P. emarginata (Douglas) Eaton variety mollis cerasus L.) as well as native bitter cherry (Prunus (Douglas) W. H. Brewer, found mostly west of the emarginata (Douglas) Eaton] (taxa authorities Cascade Mountain range in temperature coast for­ based on USDA 2010) in the northwestern United est, and P. emarginata (Douglas) Eaton variety States (Curran 1932, Simkover 1953, Frick et al. emarginata (USDA 2010), found mostly east of it in 1954). The fly is a serious quarantine pest insect for dry ponderosa pine forest (Lyons and Merilees the commercial cherry industry because all three of 1995). However, the two bitter cherry subspecies its larval instars feed on the flesh ofcherries. In 1847, occur together in some areas in the eastern slopes of introduced cherries of various varieties were first the Cascades (W. L. Yee., unpublished data). brought to Oregon (McClintock 1967), where they Rhago1etisindifferens that infest introducedcherries were reported to be infested by fly larvae in the likely originated from flies attacking bitter cherry. early 1900s (Wilson and Lovett 1913). The first However, in some areas flies infesting bitter cheny reports of infestations in introduced cherries in the rarely move onto introduced cherries even when the Yakima Valley and Wenatchee, two major cherry­ plants are close together (Mackie 1940, Eide 1947, Yee producing areas in central Washington state, were 2008), suggesting a certain degree of isolation, al­ in 1942 and 1950, respectively (Eide et al. 1949, Frick though it is unclear ifthis is true in all areas (Yee and et al. 1954). Rhagoletis indifferens has infested in­ Goughnour 2008). Large ecological, morphological, troduced cherries in Montana since at least the early and likely chemical differences between introduced 1960s (USDA 1964). The native host of the fly was and native cherries potentially could select for a va­ not known until 1932, when it was reported from riety ofdifferent life history traits among flies attack­ bitter cherry in Oregon (Curran 1932). Rhago1etis ing sweet, tart, and bitter cherries. For example, fruit on introduced cherry trees ripen earlier than those on

I USDA-ARS, Yakima Agricultural Research Laboratory, 5230 Kan­ bitter cherry trees (Mackie 1940, Jones 1942). Because nowac Pass Rd., Wapato. WA 9895!. cherry fruit Hies are univoltine, live for perhaps a 2. Corresponding author, e~mail: [email protected]. month in nature, and overwinter in an obligate pupal :I Washington State University, Vancouver, Research and Extension diapause, this could select for earlier adult eclosion Unit, 1919 NE 78th St., Vancouver, WA 98665. .. Department of Biological Sciences, 290C Calvin Life Sciences time and peak flight periods for flies infesting intro­ Bldg., University of Notre Dame, Noire Dame, IN 46556. duced versus bitter cherry trees. A similar situation

0046-225X/11l1353-1362$04.001O C 2011 Entomological Society ofAmerica