Epidemiology of grapevine anthracnose, caused by <i>Elsinoe ampelina</i>

Abstract

Abstract Anthracnose, caused by Elsinoe ampelina Shear, is an important disease of grapevines in the Auckland district. Young leaves, stems, and berries are susceptible to infection. Fully expanded leaves, and stem internodes bearing them, are highly resistant or immune. Berries become highly resistant, though not immune, about ‘50 days after anthesis, when soluble solids have risen above 5‐7% in the juice. Wetness periods necessary for infection range from 7‐10 hr at 12°c, in spring, down to 3‐4 hr at 21°c, in summer. Conidia are produced in abundance 14 days later at 12°c, and, after 5 days, at 21°c. Spore flights of up to 7 m, in wind‐borne rain‐splash drops, were detected. Conidia from overwintered cane lesions initiate the epidemic after budburst in September. After flowering, in late November‐early December, infection spreads to young berries and bunch stalks. In Auckland from October to March there are on average three or four separate rainy spells each month, each providing E. ampelina with at least one infection period. There are usually more opportunities for infection in spring than in summer or autumn. Many leaves and stem internodes produced during summer and autumn escape infection altogether. There is little spread of anthracnose on berries after January. Control of anthracnose will depend on reduction of overwintering lesions; prevention of spring build‐up of disease on leaves and stems; and protection of berries between flowering and the latter part of January.