Evaluation of Grape Rootstocks for Resistance to Type A and Type B Grape Phylloxera

Abstract

Grape rootstocks were tested for resistance to California Type A and Type B phylloxera in the laboratory and Type B phylloxera in an infested vineyard trial. The laboratory evaluations indicated that some rootstocks with partial <i>Vitis vinifera</i> parentage had resistance to both biotypes; others did not. Rootstocks with no <i>V. vinifera</i> parentage were resistant or immune to both biotypes. Field trials appear to substantiate laboratory screening results. The best levels of resistance in field trials appear to be in cultivars SO4, O39-16, and O44-4.