Anagrus (Hymenoptera: Mymaridae) egg parasitoids of Erythroneura spp. and other leafhoppers (Homoptera: Cicadellidae) in North American vineyards and orchards: a taxonomic review.

Abstract

Nine species of the mymarid wasp genus Anagrus Haliday, egg parasitoids of Erythroneura spp. and other leafhoppers associated with North American grape vineyard agroecosystems, are keyed. Two new species, A. tretiakovae and A. daanei, are described and illustrated. Discussed and corrected are the earlier published host and distribution records of A. epos Girault, which is redescribed. Host associations are indicated for all other species reviewed. It is shown that a complex of several Anagrus species is associated with leafhopper hosts found on grape vines as well as on apple, blackberry, prune, and other plants that may occur near vineyards. Leafhoppers (Cicadellidae) of the genus Erythroneura Fitch are known to be economically important pests of cultivated grape in North America (Jensen and Flaherty 1982, Martinson and Dennehy 1995). The species composition of Erythroneura in vineyards differs among major grape-growing regions. In British Columbia, grape vines (Vitis spp.) are attacked by the Virginia creeper leafhopper, E. ziczac Walsh (McKenzie and Beirne 1972), whereas in Washington, both E. ziczac and the western grape leafhopper, E. elegantula Osborn, feed upon Vitis vintfera L. (Wells et al. 1988, Cone et al. 1990). In the diverse climatic conditions of California, different varieties and cultivars of V. vintfera are grown for wine, table, and raisin grapes. One of the first records of a serious leafhopper pest problem on grapes involved what was reported as the eastern grape leafhopper, E. comes (Say) (Lockwood 1932), but represented an apparent misidentification of E. elegantula. The western grape leafhopper had been considered as a major pest of grape in San Joaquin Valley until the mid 1980's when it was largely replaced in economic importance by its near relative, the variegated grape leafhopper E. variabilis Beamer, first reported there in 1980 by Kido et al. (1984). In vineyards of California's coastal and northern counties, ?. elegantula retaines its status as the dominant leafhopper pest of grape, whereas E. variabilis is the only economically important grapevine pest in southern California, Arizona and northwestern This content downloaded from 207.46.13.71 on Wed, 27 Apr 2016 06:03:45 UTC All use subject to http://about.jstor.org/terms 78 ANAGRUS EGG PARASITOIDS Mexico (Baja California and Sonora). The leafhopper Dikrella cockerelllt (Gillette) is reported as a minor pest of grape in California's San Joaquin Valley and in Arizona (Jensen and Flaherty 1982). Varietal preferences of several Erythroneura species in New York vineyards were well analyzed by Martinson and Dennehy (1995). For many years, before E. variabilis became a problem in the San Joaquin Valley, the mymarid wasp Anagrus epos Girault had been regarded as the only species of egg parasitoid responsible for a relatively good natural control of E. elegantula in central California vineyards. However, the native Anagrus species were unable to pro vide an adequate control of E. variabilis (Settle et al. 1986, Settle and Wilson 1990). Several forms of Anagrus, known then as biotypes of A. epos, collected in Arizona, Colorado, New Mexico as well as in Baja California and Sonora, Mexico, were released and became established in selected vineyards in the San Joaquin Valley in an attempt to enhance control of E. variabilis (Gonz?lez 1988, Gonz?lez et al. 1988, Pickett et al. 1987,1989). All other studies of the species belonging to A. epos complex in North America focused on assessing their effective ness against Erythroneura species feeding on grape, as well as on looking for possible alternate leafhopper hosts within the agroecosystem of a vineyard, e.g., McKenzie and Beirne (1972) in British Columbia; Williams (1984), Settle and Wilson (1990) and Murphy et al. (1996) in California. Corbett and Rosenheim (1996a) studied dispersal of Anagrus wasps within grape vineyards in California. Because it had been assumed that overwintering adult E. elegantula females do not lay eggs that survive the cold season in central Califor nia, Doutt and Nakata (1965) suggested that A. epos wasps may overwinter by parasitizing diapausing eggs of Dikrella cruentata (Gillette) on blackberry brambles ( Rubus spp.). Subsequently, Doutt et al. (1966) and Doutt and Nakata (1973) attributed the early season abundance of A. epos in vineyards infested with E. elegantula to their proximity to a blackberry refuge. Pickett et al. (1990) summarized these and later studies on the role and effectiveness of potential refuges for grape pest management. Following earlier reports by Kido et al. (1984) and Wilson et al. (1989), they suggested that French prune trees (Prunus domestica L.) be introduced in grape agroecosystems to provide an overwintering habitat for A. epos because the prune leaf hopper, Edwardsiana prunicola (Edwards), was regarded as a good alternate host of this egg parasitoid. Although data collected by Corbett et al. (1996) and Corbett and Rosenheim (1996b) partially supported the findings of Pickett et al. (1990), the role, overwintering strategies, and species composition of Anagrus wasps in grape agroecosystems remain largely unknown. Until recent publications of Chiappini (1989) and Chiappini et al. (1996), the systematics of Anagrus was not addressed on a broad regional or worldwide level and thus correct species identification was difficult, if not impossible, without a thorough comparison of specimens with the type material which is scattered among different collections. The minute size (less than 1 mm) of Anagrus wasps that This content downloaded from 207.46.13.71 on Wed, 27 Apr 2016 06:03:45 UTC All use subject to http://about.jstor.org/terms