In South Carolina, the most destructive diseases of muscadine grapes are bitter rot, powdery mildew, angular leaf spot, and black rot. These are all fungus diseases. Bitter rot and powdery mildew attack the fruit. Angular leaf spot affects the foliage and causes early defoliation. Black rot attacks the leaves, flower clusters, and fruit.
Some varieties are naturally more resistant to a particular disease than others.
Insects causing the most damage to muscadine grapes include leaf hoppers, aphids, Japanese beetles, grapevine flea beetles, the grape curculio, and the grape berry moth. The first four feed on the leaves and the latter two attack the fruit. The grape root borer may also attack the roots of the muscadine grapes, and in some vineyards, it is the main insect problem. Contact your county Extension office for methods to control these insects and diseases. Generally, birds are a greater problem when vineyards are near trees or woodlands, when the vines have too little foliage to camouflage the fruit, and when insects are plentiful in the vineyard.