RIPE ROT
Description
Symptoms
Disease Cycle
Control

Description:
Ripe rot is a fungal disease of vinifera, French-American hybrid, and muscadine grapes that occurs primarily at ripening, and is problematic in the warm, humid grape-growing regions of the Southeast.

Symptoms:
As infected fruit mature, lesions first appear as slightly sunken or flattened rotted areas. Tiny black fruiting bodies (acervuli) develop within the lesion in a circular arrangement (Fig.1). Rotting fruit are characteristically covered with masses of sticky, pink or salmon-colored spores of the causal fungus, Colletotrichum spp. (Fig.2). As lesions expand, the entire grape eventually rots, and may drop or become shriveled or mummified as it decays.

Disease Cycle:
Ripe rot is caused by Colletotrichum gloeosporioides (sexual stage, Glomerella cingulata) and C. acutatum. The fungus overwinters in canes, pedicels and mummies (Fig. 3), and infects fruit and pedicels in the summer during any time of development. However, these infections remain inactive until the fruit ripen, after which acervuli develop and produce characteristic pink spore masses in wet weather. The disease increases rapidly and may cause severe losses as the fungus spreads from fruit to fruit during rainy periods.

Control:
Cultural - Before spring arrives, remove or disk into the soil overwintered mummies left on the trellis and ground from the previous season. Good canopy management practices are essential for management of ripe rot. Shoot thinning, leaf removal, pruning, cluster thinning, and shoot positioning are all cultural practices that open the vine canopy to air and light, reducing the amount of moisture trapped within the canopy, and allowing better penetration and spray coverage of fungicides. Muscadine varieties vary in their susceptibility to ripe rot (Table 1), there is not much information available on the relative susceptibility of bunch grapes to the disease (Table 2).

Chemical - Refer to the Winegrape Spray Program in the North Carolina Agricultural Chemicals Manual for current recommendations for ripe rot control for bunch grapes http://ipm.ncsu.edu/agchem/chptr7/706.PDF or muscadines http://ipm.ncsu.edu/agchem/chptr7/707.PDF. Where the disease is a problem, fungicide applications are critical during the period from bloom until preharvest.