HORTICULTURALENTOMOLOGY Seasonal Abundance of AphidVectors of Potato VirusY in the Red River Valley of Minnesota and North Dakota CHRISTINA D. DIFONZO,l DAVID W. RAGSDALE, EDWARD B. RADCLIFFE, NEIL C. GUDMESTAD,2 ANDGARY A. SECOR2 Department of Entomology, University of Minnesota, St. Paul, MN 55108 J. Econ.Entomol. 90(3): 824-831 (1997) ABSTRACT An epidemic of aphid-transmitted potato virus Y (PVY) in seed potato grown in the Red River Valley of Minnesota and North Dakota was the reason we began a study to determine which aphid species were found in traps placed near potato fields. Knowledge of which aphid species are present and which of these are known vectors of PVY is needed to develop management strategies that minimize virus spread. The spread of PVY to healthy indicator plants and captures of alate aphids in tile traps were monitored weekly for 3 yr consecutively (1992-1994) throughout the Red River Valley. Thirty-four aphid species were identified from green and yellow tile traps in 1992, 25 in 1993, and 26 in 1994. Yellow tile traps caught significantly more aphids overall than green tile traps and were significantly pre- ferred by Aphis helianthi Monell, Capitophorus elaeagni (del Guercio), and RllOpalosiphum l1widis (Fitch). Intervals of greatest aphid capture in green traps were generally between mid- July and mid-August at all sites in all 3 yr. Aphid captures at all sites were 3-25 times greater in 1992 and 1994 than in 1993. PVY infection of indicator plants exposed at the trapping sites also was greater in 1992 (25 plants) and 1994 (18 plants) than in 1993 (2 plants). Eighty-nine percent of PVY spread to indicator plants occurred between 8 July and 19 August. Eight species comprised 89.9% of the aphids collected in green traps during intervals of PVY trans- mission to indicator plants: Acyrthosiphon pisum (Harris), pea aphid; A. helianthi; C. elaeagni; Lipaphis erysimi (Kaltenbach), turnip aphid; R. maidis, com leaf aphid; R. padi (L.), bird cheny-oat aphid; Schizaphis graminum (Rondani), greenbug; and Sitohion avenae (F.), English grain aphid. Seven of these species were previously known PVY vectors. We found that A. helianthi transmitted PVY with low efficiency under greenhouse conditions. The 8 most com- mon aphid species were associated with crops and weeds common in the Red River Valley. Our data suggest that although the relative importance of individual PVY vectors varies from year to year and location by location, total aphid captures may be the best indicator of the risk of PVY spread. KEY WORDS Aphis helianthi, vector, epidemiology, potato, potato virus Y, Potyvirus, aphid, PVY APHID-TRANSMITIEDPOTATOVIRUSY (PVY) (Po- tyviridae: Potyvirus) is one of the most important insect vectored diseases in potato, Solanum tub- erosum L., worldwide. Acquisition and inoculation of PVY occur after epidermal probes lasting sec- onds (Bradley 1954), but infectivity is lost after a few probes (Bradley and Rideout 1953). The most efficient PVY vector is the potato-colonizing spe- cies Myzus persicae (Sulzer), the green peach aphid (MacGillivray 1981). However, as a result of its nonpersistent transmission, PVY is transmitted readily by alatae of at least 24 aphid species not colonizing the crop (de Bokx and Huttinga 1981). PVY disease epidemiology differs among potato growing regions and among years within a region, ICurrentAddress:DepartmentofEntomology, MichiganState University. EastLansing,MI. 48824-1115. 2Department of PlantPathology, NorthDakotaStateUniver- sity,Fargo,ND, 58105. depending on the aphid species present, their rel- ative abundance, feeding and host-finding behav- iors, and virus transmission efficiencies, as well as on regional cropping practices (Boiteau et al. 1988). The recognition of regional differences in PVY disease epidemiology is important because control measures are based on knowledge of local virus sources, the aphid species involved in trans- mission, and the timing of local aphid flight in re- lation to plant maturity. The Red River Valley of Minnesota and North Dakota is a leading seed potato production region in the United States. Local sources of PVY in the Red River Valley are limited. All seed potato orig- inates from disease-tested seedlings produced in tissue culture or in a tuber-unit system designed to eliminate viruses. Volunteer potato plants infected with PVY are rare because of harsh winters. Night- shade (Solanum spp.), a common weed and an al- 0022-0493/97/0824-0831$02.00/0 © 1997 Entomological SocietyofAmerica Downloaded from https://academic.oup.com/jee/article/90/3/824/2216634 by guest on 08 March 2022