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.

Anthracnose is the last common disease among vineyards. It may sometimes be called birds-eye rot. The disease causes circular spots on the leaves. The spots are dark on the outside and may be gray in the middle. The middle eventually falls out and leaves a hole in the leaf. Rainy spring weather will bring about this fungus, so to manage it be sure to weed often and prune your grape vines well.

There are also several insects that are known to attack grapevines. The first is the grape berry moth. Small green to purple caterpillars may be found in webs among the flowers and young grapes. The larvae will then enter the grapes and feed on the inside. You may notice small holes in your young grapes. The grape berry moth overwinters in a pupa within leaves that have fallen during the fall. The moths emerge in the spring and lay their eggs, and the cycle begins again. To prevent the cycle from continuing, you should remove all debris from the base of the grapevines in the fall. Destroy the debris by burning or removing from your property. If you choose, you can apply an insecticide as well to destroy any pests on the vines.

Grape Phylloxera is an insect that forms galls on the grape leaves and roots. When the grape Phylloxera affects the roots, you will notice malformed growth on the plant. Grape Phylloxera appear as very small aphid-looking insects. The eggs survive the winter and hatch in the spring. They feed on the leaf surface which results in a gall in which the female deposits their eggs. The cycle is completed once the eggs have hatched and the new insects feed on the leaves again. There are grape varieties that are resistant to the grape phylloxera, so those plants should be chosen. Insecticides will not be effective, and you will have to remove the entire plant.

Spider mites also affect grapes. You may notice leaves turning to a brown color and see webs on the underside of the leaves. Dry, hot conditions will favor these mites to develop and survive among your grapes. Be sure to properly irrigate your vineyard so that the spider mites cannot take over. In some severe cases you may need to use a miticide.

Yellow-jackets are a social breed of wasps. They build paper nests on many surfaces, including the ground and logs. They love the sweet grapes produced by the grape vines. To control the yellow-jackets be sure to harvest your grapes immediately. Do not leave any grapes on the ground as they will attack the yellow-jackets. You can trap yellow-jackets if you wish. Garden centers sell special wasp and bee traps for this purpose. Be sure to set out the traps prior to the grapes ripening. Once the fruit is out, the yellow-jackets will prefer the fruit to the traps. You can apply an insecticide specially made for wasps if you find the nest. Within a few days of application, the yellow-jackets in the nest will have died.

Keeping your vineyard nice and clean will help prevent many of these diseases and insects from plaguing your grapes. A vineyard is an attractive addition to any backyard and will produce grapes that you may use for many different things. Wine, jelly and pie are all great choices for grape use!