The bud mite and the Erineum mite of grapes

Abstract

IN THE COURSE of the investigation reported in this paper the writers became convinced that two and possibly three psysiologically distinct strains of the grape erineum mite, Eriophyes vitis (Pgst.), exist on grapes in California. These are named the bud-mite strain, the erineum strain, and the leaf-curl strain in this paper. The reasons for regarding these strains as distinct, and the methods of recognizing the symptoms they produce on grapes are given in the following report. Injury to grapevines now known to be caused by the bud-mite strain has been observed in California for at least twenty years. The minute size of the mites and the obscure nature of their attack, however, prevented the symptoms from being diagnosed definitely until 1938. In that year, H. A. Weinland, County Agent of Sonoma County, called the writers' attention to a few speci? mens of eriophyid mites associated with these same symptoms. The mites were sent to H. H. Keif er of the California State Department of Agriculture, who identified them as the common erineum mite, Eriophyes vitis (Pgst.), which had previously been associated only with irregular blisters on the upper surface of the grape leaf and felty patches of hair (erinea) on the lower surface beneath the blisters. Because the damage to the vines was so extensive and severe, and because the number of mites was so few, it seemed doubtful that the erineum mite was the causal agent. In 1938, the writers began a series of field and laboratory observations to establish the causal relationship. They have continued these observations to the present time.