We have a few numbered selections from the Cornell and Co-op series and continue to observe these. Although muscadine grapes can be grown in Arkansas without fungicides for disease control, several diseases are commonly seen in varying degrees of severity. Total crop loss is not seen although berry infection can be widespread in some locations with some varieties. The most common disease seen on muscadines is bitter rot. The bitter rot fungus can attack all green tissues, although fruit infection is most common.
Bitter rot is seen as soft rot, which rots entire berries.
Berry drop is common if the infection occurs at maturity, although early infections cause a shriveling of the berry and the fruit mummy is often retained on the vine and appears similar to black rot infected berries of bunch grapes. The most obvious way to diagnose bitter rot is to examine the rotting surface of the berry for small, black dots, which are acervuli produced by the fungus. Both bronze and black-fruited varieties are susceptible. Another fruit disease seen most years is ripe rot. This disease occurs only on fruit as they mature and ripen.