Vineyard pruning-time studies in southern California—for the season of 1950 and confirmed in 1951—have shown a relationship between pruning time in head-pruned vineyards and the incidence of so-called bud mite injury. This term was adopted in California following general acceptance of a diagnosis in which the grape bud mite, a physiological strain of Eriophyes vitis (Pgst.), was designated as the causal agent of certain growth abnormalities and crop losses in vineyards.