Diseases and Insects that May Plague Your Vineyard

Occasionally every vineyard will suffer from a variety of diseases and insects. The key to successful management is to know the signs of each disease or insect and how to rid the grapes of the cause. French wine grapes are the most susceptible to disease. Proper growing will help manage diseases, but you may need to use an occasional pesticide as well. I'll start with diseases that attack grapes, and then describe the different insects that grapes attract.

Black Rot is a disease that appears as reddish brown spots with black borders on the leaves of the grapevines. The spots may also appear on the young shoots, the stems and the tendrils. If the vine is bearing grapes, you may notice black spots on the young berries that become enlarged quickly. The black rot will rot the grapes quickly and turn then into black, shriveled corpses. The fungus that causes black rot may overwinter on the plant, and become inflamed during the wet weather of spring. To control black rot, keep a clean vineyard. Be sure to prune back the vines to allow for ample air movement. Once the plant is infected be sure to remove all fruit and foliage that is affected. If black rot continues to be a problem you may have to apply a fungicide.

Downy Mildew is also another fungus that attacks grapes. Downy mildew appears as pale yellow to greenish spots on the surface of the leaves. On the lower parts of the vines, the fungus may produce a white or gray cotton-type of growth. Grapes may turn brown and shrink and wrinkle when affected by downy mildew. The same prevention and maintenance rules that applied for black rot apply also for downy mildew. Powdery mildew is similar to downy mildew but attacks the grapes during dry weather. The best way to manage powdery mildew is to purchase varieties that are resistance to this fungus. Good air circulation and a clean vineyard will help prevent this fungus from attacking. Fungicide may need to be applied to solve the problem of powdery mildew.