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Ripe rot

Colletotrichum spp.

Initially, berries show circular, reddish brown spots, which enlarge to cover the whole fruit. Salmon-pink fungal spore masses develop in a circular pattern on the fruit surface. The berries shrivel and darken as they decay and then fall to the ground. Berries are susceptible to infection at all stages of development but do not show symptoms until the berries are ripe. Disease development is favored by wet weather and temperatures of 77 to 86ºF (25 to 30ºC). The fungus overwinters in mummified fruit and infected pedicels, from which spores are dispersed in spring and early summer. Spores produced on rotting berries can infect neighboring berries.

Distribution

Ripe rot occurs in most grape-growing areas but is most common in warm, humid regions.

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