By parasitizing the roots of Vitis species, grape phylloxera (Daktulosphaira vitifoliae Fitch, Phylloxeri-dae) is one of the most devastating pests in viticulture. Grafting susceptible scions (Vitis vinifera) to tolerant Vitis rootstocks is a common practice to control grape phylloxera in wine growing regions worldwide. However , grape phylloxera populations still develop on the roots of most grafting combinations. Questions remain as to whether or not the impact of environmental factors on

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... e phylloxera population dynamics is related to Vitis rootstock cultivars. In the presented field study, we investigated the influence of two closely related mature Vitis berlandieri x Vitis riparia rootstock varieties on the relations between the dynamics of root feeding grape phylloxera populations, root morphology and abiotic factors. The investigation took place on a commercial vineyard in Geisenheim/Germany on Teleki 5C/V. vin-ifera 'Weisser Riesling' and Kober 125AA/V. vinifera 'Weisser Riesling'. Samples of roots, attached grape phylloxera populations and soil were taken in the field 19 times between August 2007 and August 2009. Grape phylloxera population structure was recorded by the occurrence of root-feeding wingless females, funda-trices and nymphs and the pigmentation and position of root galls were assessed. Root morphological parameters were assessed using WinRhizo Pro. Soil abiotic parameters were assessed in the laboratory. Results of a principal component analysis showed rootstock related differences considering the impact of abiotic factors on grape phylloxera population structure. Especially soil temperature and soil organic matter were indicated to have a lower impact on grape phylloxera population structure on roots of 5C than on roots of 125AA. Our data indicate that ecological factors have a lower impact on the development of grape phylloxera on more supportive rootstocks. K e y w o r d s : Vitis berlandieri x Vitis riparia; insect population dynamics; Phylloxeridae, rootstocks.