Distribution and host plants of the blueberry maggot fly, Rhagoletis mendax (Diptera: Tephritidae) in southeastern North America

To better determine the geographic range, pattern of host plant usage and phenology of Rhagoletis mendax, the blueberry maggot fly, an extensive set of rearings from fruit of Vaccinium and Gaylussacia (Ericaceae) species was made, primarily from natural populations of these host plants. Collecting focused on the relatively unstudied southeastern United States, although fruit collections as far north as Michigan and as far west as Texas were made. The known range of the blueberry maggot fly has been extended west to the Ozark Plateau, and the fly is now known to be much more widely distributed in southeastern North America than previously thought. Although R. mendax infests many species of Vaccinium and Gaylussacia in the northernmost part of its range, in most of its range it infests almost exclusively V. stamineum (deerberry). The relatively inflexible dia pause characteristics of R. mendax may contribute to this restriction in host plant usage. The blueberry maggot fly, Rhagoletis mendax Curran, is a serious native pest of blueberries {Vaccinium L. spp.), primarily in northeastern North America (Lathrop and Nickels, 1932; Bush, 1966). The economic importance of R. mendax notwithstanding, its geographic range and use of native host plants remain poorly known, especially in the southern part of its range. Bush (1966) lists only 12 localities of R. mendax in the southern United States, and specific host plant information is lacking for many of the specimens. Moreover, most of the Florida specimens mapped in Bush (1966) are actually not R. mendax, but are instead a new species of the R. pomonella species group that is restricted to V. arboreum Marshall. This species is discussed elsewhere (Payne and Berlocher, 1995). Better information about R. mendax is desirable for both practical and basic reasons. Commercial blueberry production is increasing in the southern United States. In 1986, there were 2059 hectares of improved cultivars of rabbiteye blueberries, V. ashei Reade, in production in 10 southeastern and mid-south states (Payne et al., 1988). In 1989, there were about 14,000 hectares of highbush blueberries, V. corymbosum L., in the U.S.A. with the largest production areas in New Jersey, Michigan, and North Carolina (Hancock and Draper, 1989). While R. mendax infestation of commercial rabbiteye blueberries in the South is rare, it may be on the rise (Payne et al., 1993). On the basic side, complete host plant information is needed to understand the population genetics of host race for mation, an area of study to which Rhagoletis species have made substantial con tributions (Feder et al., 1988; McPheron et al., 1988). Here we present new geographic range and host plant data on R. mendax, focusing on Vaccinium and Gaylussacia Humboldt, Bonpland, and Kunth (huck leberry) species in the southeastern North America. However, some collections 1 USDA-ARS, Southeastern Fruit and Tree Nut Research Laboratory, 111 Dunbar Road, Byron, Georgia 31008. 2 Department of Entomology, 320 Morrill Hall, University of Illinois, 505 S. Goodwin Ave., Urbana, Illinois 61801. Accepted for publication 8 August 1994. This content downloaded from 207.46.13.168 on Sat, 09 Apr 2016 06:33:39 UTC All use subject to http://about.jstor.org/terms 134 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY were also made in other poorly sampled areas, such as the Ozark Plateau and the midwestern United States. Materials and Methods Collections were made on seven automobile trips by S.H.B. during summer and fall 1989-1991, and on numerous trips by J.A.P. during 1985-1991 (Payne et al., 1989). All flies were reared from infested fruit. Most fruit collections were effectively random samples from all Vaccinium and Gaylussacia species at a site that had ripe or ripening fruit; only a few of the samples were seen to be obviously infested in the field. Ripening fruit was considered to be fruit beginning to show color. Fallen but non-decayed fruit occurring in collectible numbers was harvested and pooled with fruit picked form plants. Number of fruit collected was approx imated by weighing (Berlocher and Enquist, 1993). The emphasis was on wild host plants growing under natural conditions, with multispecies sites being especially sought out. However, some collections from domesticated cultivars of highbush blueberry, V. corymbosum, and rabbiteye blueberry, V. ashei, were included to obtain phenological information. The do mesticated plants were sampled from both cultivated and formerly cultivated, abandoned plantings. In addition, some undomesticated species and interspecies hybrids growing under cultivation were collected. Fly samples were used for multiple purposes. Larvae were frozen for enzyme electrophoresis (Berlocher, 1995), DNA analysis, and immature morphological studies, and adults were reared for phenological and morphological analyses (studies to be described elsewhere). This multiple use of material affected iden tification of material. At some sites with few fruit and low infestation rates, all material was saved as frozen larvae; at such sites, identification was based on electrophoretic characters (Berlocher et al., 1993). At most sites, however, adults were reared as described by Berlocher and Enquist (1993) for R. pomonella. Adult flies were identified following Bush (1966). Herbarium samples and plant photographs were taken at many of the sites. Herbarium samples are deposited in the Herbarium of the University of Illinois at Urbana-Champaign. The primary reference for plant identification was Vander Kloet's (1988) monograph of Vaccinium and Luby's et al. (1991) chapter on blueberries and cranberries. Regional floras were used as supplemental references for Vaccinium, and to identify Gaylussacia species. Insect vouchers (adult flies) for sites yielding sufficient adults have been deposited in the collection of the Illinois Natural History Survey. Collection sites are described in Table 1. Sites are named using nearest prin cipality or other landmark, but are not necessarily exactly at that point; for ex ample, the two Florida state park collections in Table 1 were actually from road sides outside the parks. A variety of cultivars of V. corymbosum and interspecific hybrids involving this species, collected separately, were pooled together for the N.C. State Sandhills Research Station site in Table 1, as all were uninfested. Additional details for sites included in the electrophoretic study are in Berlocher (1995); for other sites, contact the authors. Statistical testing of independence of whether a sample was infested or not, and date of collection, was carried out using contingency analysis. Instead of the familiar contingency x2> a Monte Carlo program (Macintosh) that simulates an This content downloaded from 207.46.13.168 on Sat, 09 Apr 2016 06:33:39 UTC All use subject to http://about.jstor.org/terms VOLUME 68, NUMBER 2 135 Table 1. Locality, date, and host plant species data for Rhagoletis mendax in eastern North America. Infestation rate is the number of larvae or pupae divided by the number of fruit collected. D indicates domesticated plants originally under cultivation, regardless of current cultivation condition, and C indicates wild plants under cultivation (see text). State/ Site (County) Date collected Host species No. fruit Infest, coll. rate (%)