Crown gall occurs on over 600 species of plants. The disease is characterized by galls or overgrowths that form on the roots, trunk, and arms of grape vines. V. vinifera cultivars are more susceptible to crown gall than V. labrusca cultivars. These galls are mostly found on the lower truck near the soil line. Large galls can develop rapidly and completely girdle a young vine in one season. When galls are numerous or when they are located on major roots or on the root crown, they disrupt the translocation of water and nutrients, leading to poor growth, gradual dieback, and sometimes death of the vine. In general, affected plants are more susceptible to adverse environmental conditions, especially winter injury.

Symptoms

The major symptom of crown gall is the fleshy galls. Large galls may develop rapidly and completely girdle young vines in one season. Galled vines frequently produce inferior shoot growth, and portions of the vine above the galls may die. Current-season galls are first apparent in early summer as white, fleshy, callus growth. Galls turn brown by late summer and in the fall become dry and corky. The crown gall bacterium is systemically present in the vast majority of grape vines, but seldom causes disease unless the vine in injured.

Disease Cycle

The disease organism is the soil-borne bacterium Agrobacterium tumefaciens. The bacterium survives for long periods of time in soil, within galls and within infested vines. A fresh wound is required for gall formation to start in the grapevine. Contaminated planting material (nursery stock) is another source of the disease.

Disease Management

Because the bacterium lives in the soil it cannot be controlled by chemical sprays. It is necessary to examine new plants before planting and discard any that have galls. In the vineyard, remove large galls on the upper parts of the trunk or on the arms by pruning the arm or trunk below the affected tissue and renew the vine by means of a shoot from the base of the vine.

Budding and grafting are injuries that occasionally elicit disease development at those wounding sites, but cold injury is by far the most important factor in the Northeast. Therefore, management practices that minimize the risk of cold injury are currently the only practical technique for managing the disease. These include careful site selection for cold-sensitive cultivars and cultural practices that promote winter hardiness. Hilling above the union of grated vines protects buds from freezing and ensures the development of new scion shoots that may be needed for trunk renewal. The use of multiple trunk vines and yearly replacement of dead trunks with renewals helps to manage the disease at a tolerable level. In some areas growers bury young vines in the fall to reduce freeze injury.