Colonization of New York Vineyards by Anagrus spp. (Hymenoptera: Mymaridae): Overwintering Biology, Within-Vineyard Distribution of Wasps, and Parasitism of Grape Leafhopper, Erythroneura spp. (Homoptera: Cicadellidae), Eggs

Abstract

A study was conducted in New York to identify the Anagrus species present in vineyards, to determine the plants in which Anagrus species overwinter, and to characterize the dispersal of wasps and level of parasitism of grape leafhopper eggs in vineyards. Anagrus daanei S. Triapitsyn and Anagrus erythroneurae S. Trjapitzin and Chiappini were the most abundant species reared from Vitis labrusca Bailey and Vitis vinifera L. cultivars, respectively. V. labrusca cultivars are infested predominantly by Erythroneura comes (Say), whereas V. vinifera cultivars are infested primarily by the Erythroneura vitifex Fitch–Erythroneura bistrata McAtee complex. Anagrus tretiakovae S. Triapitsyn was reared from seven grape cultivars in approximately equal proportions. Thus, A. daanei and A. erythroneurae appear to possess greater degrees of host specificity than A. tretiakovae. These results support the belief that, although Anagrus species have relatively broad host associations, host preferences do exist. These preferences may be mediated by the plant associations of particular leafhopper species. Anagrus species use alternate hosts that infest several plant species. In particular, diapausing insect eggs in Acer saccharum Marshall, Robinia pseudo-acacia L., Rosa multiflora Thunberg, Salix nigra L., Vitis riparia Michaux, and Zanthoxylum americanum Miller may play important roles in the overwintering biology of the Anagrus species that are most abundant in vineyards. Following emergence from overwintering hosts, Anagrus adults are aggregated at the vineyard edge early in the season (May and June). By midseason or later (August and September), the pattern of wasp colonization and parasitism indicates that parasitoids are more widely dispersed in the vineyards. This pattern is consistent with colonization from vineyard edges, followed by relatively slow dispersal into the vineyard interior. Further investigations are necessary to identify the alternate host(s) that Anagrus exploits during the winter and spring and to delineate the phenology of such alternate hosts, as well as that of the grape leafhoppers and Anagrus species in the spring. Habitat management studies could then be conducted to identify strategies that would accelerate population growth of Anagrus in the spring and increase the rate of dispersal into vineyards.