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 st ructure of native grape phylloxera. Daktulosphaira vitifoliae (Fitch), Viti s species in 22 central and eastern U.S. states were surveyed for grape phy lloxera presence and abundance. Data for frequency of attack and mean numbe r of galled leaves per vine were compared among Vitis species and among six geographic regions defined according to topographic, ecological, and heuri stic criteria. Four of the seven Vitis species that were identified had bee n attacked by grape phylloxera and both the frequency of vines that were at tacked and the mean number of galled leaves differed among species and regi ons. In general, V. riparia (Michaux) and V. vulpina (L.) were attacked mor e frequently than expected and V. cinerea (Englemann) less than expected. T he distributions of three of these species, V. vulpina, V. aestivalis (Mich aux),and V. cinerea, were largely overlapping, but the distribution of V. r iparia 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 Gul f 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 t o this trend. In addition, sexual morphs were produced by apterous gallicol ae in galls on V. cinerea but not on other Vitis species. This life cycle v ariant has previously been described only in the southwest United States. T hese data will be useful for future molecular phylogeographic studies and i n the understanding, evaluation, and deployment of phylloxera resistant ger mplasm.