Surveys conducted in the South Okanagan Valley, British Columbia, revealed that a new leafhopper pest of grapes, the western grape leafhopper (WGL), Erythroneura elegantula Osborn, was widespread and often abundant in Vineyards on the east side of the Valley from just north of Penticton south to the United States border. Infestations occurred on drier upland sites where most commercial grape production occurs. The largest populations of up to 40 nymphs per leaf were recorded from commercial Vineyards that had applied reduced rates of the insecticide carbaryl for control of the Virginia creeper leafhopper, E. ziczac Walsh

Judd, Gary J. R.

Lowery, D. Thomas

English

Journal of the Entomological Society of British Columbia

J. ENTOMOL. SOC. BRIT. COLUMBIA 104, DECEMBER 2007  3  First record of the Western Grape Leafhopper,  Erythroneura elegantula Osborn (Homoptera: Cicadellidae), in Canada D. THOMAS LOWERY1 and GARY J.R. JUDD1 ABSTRACT Surveys conducted in the South Okanagan Valley, British Columbia, revealed that a new leafhopper pest of grapes, the western grape leafhopper (WGL), Erythroneura elegan-tula Osborn, was widespread and often abundant in vineyards on the east side of the valley from just north of Penticton south to the United States border.  Infestations oc-curred on drier upland sites where most commercial grape production occurs.  The larg-est populations of up to 40 nymphs per leaf were recorded from commercial vineyards that had applied reduced rates of the insecticide carbaryl for control of the Virginia creeper leafhopper, E. ziczac Walsh. Key Words: Western Grape Leafhopper, Erythroneura elegantula, distribution INTRODUCTION The western grape leafhopper (WGL), Erythroneura elegantula Osborn, is often considered the most important insect pest of grapes in the western United States as far north as southern Washington State (Wolfe 1955, Jensen and Flaherty 1981). Believed to be native to coastal California where it feeds on a species of wild grape, Vitis cali-fornica Bentham (Doutt and Nakata 1965), WGL is now found in most commercial vineyards throughout the western U.S. (Wells and Cone 1989). Previous research and surveys of arthropod pests of grape did not record WGL in vineyards in the south Okanagan and Similkameen Valleys of British Columbia (Madsen and Morgan 1972, McKenzie and Beirne 1972), and it had not been found elsewhere in Canada (Beirne 1956). As recently as 2000, the BC Management Guide for Grapes did not in-clude WGL in its list of grape pests (BCMAFF 2000). While conducting research on parasitism of Virginia creeper leafhopper (VCL), E. ziczac Walsh, eggs by Anagrus daanei Tri-apitsyn (Hymenoptera: Mymaridae) in South Okanagan vineyards in 1998 (Lowery et al. 2007) an unusual leafhopper was discovered and later confirmed to be WGL. This paper reports on the results of a survey conducted in south central BC to establish the distribution and abundance of this new leafhopper pest of grapes.  1 Agriculture and Agri-Food Canada, 4200 Hwy 97, Box 5000, Summerland, BC  V0H 1Z0 MATERIALS AND METHODS Following verification that WGL had invaded the south Okanagan, during 1998 to 2003, leaves from commercial, wild and backyard grapes located in the main pro-duction areas from Kelowna south to the United States border and in the Simil-kameen Valley near Cawston and Kereme-ous were collected and brought to the labo-ratory for examination. A smaller number of samples was also collected from Virginia creeper, Parthenocissus quinquefolia (L.) Planchon, and Boston ivy, P. tricuspidata (Siebold and Zuccarini), vines.  Leaves were initially inspected in the field and only 4  J. ENTOMOL. SOC. BRIT. COLUMBIA 104, DECEMBER 2007   WGL nymphs were first collected in early July, 1998, in a commercial vineyard south of Penticton on the east side of Skaha Lake, Okanagan Valley, BC (49º 23' 23" N, 119º 33' 24" W). By mid-July nymphs showed pale yellow spots on the dorsum of the thorax and eyes appeared pale rather than dark red as for VCL. When adults ap-peared at the end of July specimens were sent to Dr. K.G.A. Hamilton, Agriculture and Agri-Food Canada, Eastern Cereals and Oilseeds Research Centre, Ottawa, for spe-cies verification. Voucher specimens are retained in the Canadian National Collec-tion of Insects, Ottawa.  Characters for distinguishing nymphs of WGL from VCL are included in Wells and Cone (1989). Briefly, WGL have a whiter body colour, paired diffuse yellow spots on the dorsum of each thoracic segment in the last instar, pronounced pairs of setae on the dorsum of each abdominal segment, and pale rather than red eye colouration. The paired markings on the thorax of last instar VCL nymphs are larger and brown or red-dish brown in colour. Adult WGL retain the paler body colour and pale eyes, and mark-ings on the body and wings are red or red-dish brown rather than brown. From 1998 to 2003, nearly 80 commer-cial vineyards and 20 locations having wild grapes, table grapes or ornamental Vitaceae were sampled at least once in the Okanagan and Similkameen Valleys for WGL. This new pest was found to be widely distributed throughout the east side of the Okanagan Valley from just north of the city of Pentic-ton (49º 31' 24" N, 119º 34' 13" W) south to the US border (Fig. 1). Infestations oc-curred on the drier areas away from the valley bottom. The main production areas for commercial grapes also occur in the drier upland areas.   WGL infests grapes throughout south-central WA (Wells and Cone 1989), but we are not aware if this species occurs in the northern part of the state.  McKenzie (1973) reported that VCL was the only leafhopper pest of grapes found in the Okanagan Val-ley, BC. Two of the sites in this 1972 study were located south of Oliver within the current WGL distribution zone (Fig. 1). He did not survey any vineyards located be-tween Penticton and Okanagan Falls, how-ever, where the largest populations of this leafhopper were located in 1998.   Reports of leafhopper damage likely attributable to WGL dating back to the mid 1990s and the relatively widespread current distribution of this leafhopper suggests that it arrived in the Okanagan Valley many years before 1998. It is possible that small numbers of WGL have existed in BC for a much longer period of time and that only recently has the population expanded in response to warmer weather and an industry shift from hybrid varieties to more favour-able vinifera varieties. Prior to 1990, most Okanagan and Similkameen vineyards were of French hybrid and Vitis labrusca varie-ties, which were found to be more hardy, productive, and resistant to pests and dis-eases (Bowen et al. 2005). Oviposition by VCL is lower on American varieties of V. labrusca than on V. vinifera, and younger nymphs often become entangled in the hairs brought to the lab if leafhoppers were pre-sent. For commercial vineyards, a minimum of five leaves infested with leafhoppers was collected from five locations per vineyard, while five to 10 infested leaves were sam-pled from individual grape or ornamental vines.   Numbers of WGL and VCL were also monitored approximately weekly through-out spring and summer in vineyards located between Penticton and north Osoyoos where WGL was first discovered. Six yel-low sticky traps (7.5 x 13 cm, PheroTech Inc., Delta, BC) per vineyard were used to monitor adult leafhoppers. Nymphs of WGL and VCL were also counted on leaves sampled randomly from the infested zone (BCMAL 2006) and inspected in the labo-ratory under a magnifying lens.  RESULTS AND DISCUSSION J. ENTOMOL. SOC. BRIT. COLUMBIA 104, DECEMBER 2007  5  of American grapes (McKenzie and Beirne 1972).   VCL have shorter developmental times than WGL and, therefore, occur more com-monly at higher latitudes than WGL (Wells and Cone 1989). WGL is currently found in the upland portions on the east side of Okanagan and Similkameen viticultural regions 5, 3 and the southern portion of region 2, as designated by Bowen et al. (2005). The relatively higher temperatures in parts of these regions might partially explain the current distribution of this leaf-hopper, but it does not explain the absence of WGL from other areas, such as region 4 (Golden Mile), that are as warm as, or warmer than, infested areas farther north.   WGL was detected at only one of nine sites of non-commercial grapes or Virginia creeper vines located within the infested zone (data not shown). At this one site, only three nymphs were found on a sample of 10 leaves collected from one vine in north O.K. Falls. In certified organic vineyards and in unsprayed grapes and ornamental vines, populations were generally low, rarely exceeding one nymph per leaf (Table 1) or one adult per trap per day (Table 2).  Numbers of WGL in the two organic vine-yards might have been influenced by their close proximity to conventional vineyards that had large numbers of this pest. The highest densities of WGL were recorded in conventional vineyards. In certain areas of one vineyard located adjacent to the initial discovery site (north O.K. Falls 2), numbers of first generation WGL exceeded 40 nymphs per leaf in July. Very little green leaf material was evident on the leaves of these vines by the end of the season. Peak numbers in the monitored area of this vine-yard were 24.1 nymphs per leaf (Table 1) and 15.9 adults per trap per day (Table 2).  Discussions with this grower indicated that a serious leafhopper problem had occurred for several years previously. This and a second vineyard (south Penticton 1) with high numbers of WGL had both been sprayed repeatedly with reduced rates of carbaryl that had been used effectively to control VCL. Monitoring of conventional vineyards suggested that recommended rates of car-baryl provided some control of WGL.  Other than the two organic vineyards and the two conventional vineyards treated with reduced rates of carbaryl (south Penticton 1, north O.K. Falls 2), the vineyards were treated with carbaryl at full rates to at least Figure 1.  Current distribution of the west-ern grape leafhopper, Erythroneura elegan-tula, on the east side of the Okanagan Val-6  J. ENTOMOL. SOC. BRIT. COLUMBIA 104, DECEMBER 2007   Table 1. Numbers of western grape leafhopper (WGL), Erythroneura elegantula, and Virginia creeper leafhopper (VCL), E. ziczac, nymphs / leaf in commercial vineyards located on the east side of the Okanagan Valley ranging from Penticton in the north to Osoyoos in the south based on monitoring conducted during 1998 to 2003.     Location Date1 (y/m/d) Production practice WGL VCL south Penticton 1 99/07/14 conventional  6.2  33.3 south Penticton 2 01/07/19 conventional  2.0  3.8 north O.K. Falls 1 98/07/06 organic  0.9  8.1 north O.K. Falls 2 99/07/15 conventional  24.1  18.3 north O.K. Falls 3 98/09/09 conventional  1.4  0.2 south O.K. Falls 1 01/08/30 conventional  1.5  <0.1 south O.K. Falls 2 01/08/30 conventional  1.7  0.6 south O.K. Falls 3 99/07/14 organic  0.7  22.3 north Osoyoos 1 02/06/24 conventional  0.1  1.1   Avg. no. nymphs/leaf    1Except for north O.K. Falls 3, which was sampled only once, dates relate to peak numbers of WGL nymphs recorded during the year of monitoring when the leafhopper was first recorded at that location. Table 2. Numbers of adult western grape leafhopper (WGL), Erythroneura elegantula, and Virginia creeper leafhopper (VCL), E. ziczac, Adults / sticky trap / day in commercial vineyards located on the east side of the Okanagan Valley ranging from Penticton in the north to Osoyoos in the south based on monitoring conducted during 1998 to 2003.     Location Date1 (y/m/d) Production practice WGL VCL north Penticton 02/05/23 conventional  0.1  0.5 south Penticton 1 99/06/16 conventional  10.1  51.7 south Penticton 2 01/05/16 conventional  0.1  30.4 south Penticton 3 01/05/16 conventional  0.1  4.1 south Penticton 4 01/05/16 conventional  <0.1  0.2 north O.K. Falls 1 98/07/31 organic  0.8  43.1 north O.K. Falls 2 99/06/16 conventional  15.9  14.3 north O.K. Falls 3 98/08/13 conventional  0.3  0.1 north Osoyoos 3 01/07/23 conventional  <0.1  0.8   Avg. no. nymphs/leaf    south O.K. Falls 1 01/08/07 conventional  1.4  8.5 south O.K. Falls 2 01/05/29 conventional  0.1  1.5 south O.K. Falls 3 99/08/18 organic  0.5  18.8 north Osoyoos 2 01/05/08 conventional  <0.1  0.6 1 All locations were monitored more than once. Dates shown relate to peak numbers of adult trapped during the year of monitoring when the leafhopper was first recorded at that location. J. ENTOMOL. SOC. BRIT. COLUMBIA 104, DECEMBER 2007  7  those portions where leafhopper numbers were damaging (Table 1, 2). Leafhopper populations in these vineyards were rela-tively low, but numbers of WGL often ex-ceeded those of VCL, suggesting that the former species may be less affected by car-baryl. Resistance of WGL to various insec-ticides has been reported previously (AliNiazee et al. 1971). The first report concerned the failure of DDT to control this pest on grapes in California in 1952 (Stafford and Jensen 1953).  Parasitism of WGL by the egg parasi-toid Anagrus erythroneurae, which over-winters in eggs of leafhoppers on plants in the families Rosaceae and Betulaceae (Lowery et al. 2007), might limit the range of WGL in the Okanagan Valley. Most vineyards on the east side of the valley that are infested with WGL are located adjacent to uncultivated areas dominated by sage-brush; there are few host plants that support overwintering A. erythroneurae. Reduced rates of carbaryl used to control VCL (BCMAFF 2000) likely caused the ob-served outbreaks of WGL in south Pentic-ton 1 and north O.K. Falls 2. Reduced-rate sprays were ineffective for the control of WGL, but they would have reduced num-bers of A. erythroneurae. Numbers of WGL quickly dropped below 1 nymph per leaf (data not shown) after the insecticide pro-gram was altered to a single well-timed spray to less than 10% of the vineyard where the heaviest infestation occurred. The effectiveness of insecticides for the control of WGL needs to be re-evaluated, and growers will have to consider altering their spray practices where WGL occurs.  ACKNOWLEDGEMENTS  We thank Hugh Philip, Provincial Ento-mologist, BC Ministry of Agriculture, Fish-eries and Food, Kelowna, for his assistance with the survey, and also the many growers that allowed us to monitor their grapes.  Technical assistance was provided by Karin Todd, Jocelyn Gartrell, Lisa Wambold and Lauren Bunckle.  We are grateful to Dr. Andy Hamilton, AAFC-ECORC Ottawa, for the leafhopper identifications.  Funding for this project was provided by the British Columbia Wine Institute and Agriculture and Agri-Food Canada through the Match-ing Investment Initiative, the National Re-search Council of Canada Industrial Re-search Assistance Program, and the BC Investment Agriculture Foundation.  REFERENCES AliNiazee, M.T., M.H. Frost Jr., and E.M. Stafford. 1971. Chemical control of grape leafhoppers and spider mites on grapevines. Journal of Economic Entomology 64: 697-700.  BCMAFF. 2000. Management Guide for Grapes for Commercial Growers, 2000-2001 Edition. British Co-lumbia Ministry of Agriculture, Fisheries, and Food. March 2000.  BCMAL 2006. 2006 Best Practices Guide for Grapes for British Columbia Growers, British Columbia Ministry of Agriculture and Lands. May 2006.  Beirne, B.P. 1956. Leafhoppers (Homoptera: Cicadellidae) of Canada and Alaska. The Canadian Entomolo-gist 88, Supplement 2.  Bowen, P.A., C.P. Bogdanoff, B.F. Estergaard, S.G. Marsh, K.B. Usher, C.A.S. Smith and G. Frank. 2005. Geology and wine 10: use of geographic information system technology to assess viticulture performance in the Okanagan and Similkameen Valleys, British Columbia. Geoscience Canada. 32: 161-176. Doutt, R.L. and J. Nakata. 1965. Parasites for control of grape leafhopper. California Agriculture 19: 3-5. Jensen, F.L. and D.L. Flaherty. 1981. Grape leafhopper, pp. 98-110. In D.L. Flaherty, F.L. Jensen, A.N. Kasimatis, N. Kido and W.J. Moller (eds.), Grape Pest Management. Agricultural Sciences Publications 4105, University of California, Berkeley.  Lowery, D.T., S.V. Triapitsyn and G.J.R Judd. 2007. Leafhopper host plant associations for Anagrus (Hymenoptera: Mymaridae) parasitoids in the Okanagan Valley, British Columbia. Journal of the Ento-mological Society of British Columbia 104: 9-16. Madsen, B.J. and C.V.G. Morgan. 1972. Mites and insects collected from vineyards in the Okanagan and 8  J. ENTOMOL. SOC. BRIT. COLUMBIA 104, DECEMBER 2007   Similkameen Valleys, British Columbia. Journal of the Entomological Society of British Columbia 72: 9-14. McKenzie, L.M. and B.P. Beirne. 1972. A grape leafhopper, Erythroneura ziczac (Homoptera: Cicadelli-dae), and its mymarid (Hymenoptera) egg-parasite in the Okanagan Valley, British Columbia. The Cana-dian Entomologist 104: 1229-1233. McKenzie, L.M. 1973. The Grape Leafhopper, Erythroneura ziczac (Homoptera: Cicadellidae) and its My-marid (Hymenoptera) Egg-Parasite in the Okanagan Valley, British Columbia. M.Sc. Thesis, Simon Fraser University, Burnaby, British Columbia, Canada. Stafford, E.N. and F.L. Jensen. 1953. Grape leafhoppers gain resistance to DDT. Western Fruit Grower, March 1953. Wells, J.D. and W.W. Cone. 1989. Biology of Erythroneura elegantula and E. ziczac (Homoptera: Cicadel-lidae) on Vitis vinifera in southcentral Washington. Journal of the Entomological Society of British Co-lumbia 86: 26-32. Wolfe, H.R. 1955. Leafhoppers of the state of Washington. Washington Agricultural Experimental Station Circular 277, Washington State Department of Agriculture, Pullman, WA.  

First record of the Western Grape Leafhopper, Erythroneura elegantula Osborn (Homoptera: Cicadellidae), in Canada

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First record of the Western Grape Leafhopper, Erythroneura elegantula Osborn (Homoptera: Cicadellidae), in Canada

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