Distribution and abundance of leaf galling and foliar sexual morphs of grape phylloxera (Hemiptera: Phylloxeridae) and Vitis species in the central and eastern United States

To Letter understand the host range and factors acting on the population structure of native grape phylloxera. Daktulosphaira vitifoliae (Fitch), Vitis species in 22 central and eastern U.S. states were surveyed for grape phylloxera presence and abundance. Data for frequency of attack and mean number of galled leaves per vine were compared among Vitis species and among six geographic regions defined according to topographic, ecological, and heuristic criteria. Four of the seven Vitis species that were identified had been attacked by grape phylloxera and both the frequency of vines that were attacked and the mean number of galled leaves differed among species and regions. In general, V. riparia (Michaux) and V. vulpina (L.) were attacked more frequently than expected and V. cinerea (Englemann) less than expected. The distributions of three of these species, V. vulpina, V. aestivalis (Michaux),and V. cinerea, were largely overlapping, but the distribution of V. riparia was not. It was found, to the near exclusion of other species in the northern United States, in the region formerly occupied by the Laurentide Icesheet. An increasing south to north gradient in phylloxera abundance was observed. Fourteen per cent of the surveyed vines were attacked in the Gulf Coast, 34% in the Central region, and 66 and 64% in the Northcentral and Northeastern regions. The mean number of galled leaves per vine conformed to this trend. In addition, sexual morphs were produced by apterous gallicolae in galls on V. cinerea but not on other Vitis species. This life cycle variant has previously been described only in the southwest United States. These data will be useful for future molecular phylogeographic studies and in the understanding, evaluation, and deployment of phylloxera resistant germplasm.