Grapes are a popular fruit crop for home gardeners as well as an important commercial crop. Different varieties of grapes are suitable for fresh fruit, cooking, juices or wines. In general, grape vines grow best in full sun in areas with mild winters. They require moderately fertile, well-drained soil. Some varieties of grape vines will tolerate more heat or cold than other varieties. Grape vines are susceptible to numerous diseases, pests and environmental stresses. You should choose disease-resistant grape vines that are suited to your climate and that produce the type of fruit you desire.
Many fungal diseases cause leaf and cane spots or blotches on grape vines as well as fruit rots. Fungal diseases also cause limb dieback, crown galls and root rots. Some fungal diseases can be prevented or controlled with regular applications of a fungicide according to the manufacturer’s directions. Nematodes spread soil-borne viruses that infect grape vines and cause them to decline. There is no treatment for viruses. The vines need to be removed and destroyed to prevent the spread of the disease, and the soil needs to be fumigated to kill the nematodes.
Some pests cause minimal damage to grape vines, while others can decimate an entire vine or crop. The roots of grape vines are susceptible to attack by grape root borers and grape rootworms. Beetles, hornworms, leafhoppers and mites chew on the foliage, and beetles and worms attack the buds. The fruit, especially when ripe, attracts fruit flies, lady beetles, mealybugs and yellow jackets. The use of a pesticide applied at the rate recommended by the manufacturer may help deter or kill pests.
Low soil fertility and nutrient deficiencies can result in poor vine growth and fruit production. Some nutrients that are often deficient include boron, iron, magnesium, manganese, nitrogen and potassium. Poor flowering may be the result of too much shade, while extremely hot or cold temperatures may cause lack of fruit. Fruit can be damaged by sunscald if it is exposed to direct sunlight. Freezing temperatures or frost can damage foliage and buds.