Nectria Twig Blight

Causal Agent

• Nectria twig blight is primarily a disease of apple trees and is caused by the Nectria cinnabarina fungus. The disease symptoms start to appear on trees between late May to early June. It is important to understand the symptoms of nectria twig blight as the disease is frequently confused with fire blight. Fire blight is a serious disorder that requires different management practices.

Symptoms

• The disease is characterized by the appearance of small, sunken lesions or cankers on small twig and branches. With disease progression, the canker girdles the entire stem and kills it. The foliage above the affected area wilts and dies. Damage is most severe between the middle and end of summer. Mature cankers start to reveal bright orange to red, 1/8 to 1/6-inch-wide, fruiting bodies. The presence of these fruiting bodies differentiates the disease from fire blight.

Favorable Conditions

• Fungal growth of nectria twig blight is favored by 70 degree Fahrenheit weather. The growth rate tends to slow at temperatures of 80 to 85 F. Trees that have unhealed wounds from fruit harvest time coupled with extended moist weather following harvest are highly prone to the infection. Certain apple varieties that have a large, cluster-bud base are especially susceptible. These include Rome Beauty, Northern Spy and Ben Davis.

Control

• Nectria twig blight is considered a minor disorder that does not seriously threaten tree health. There are no chemical control strategies for the disease. Prevention includes keeping tree in good health with proper cultural management. Prune trees properly to minimize damage and to speed up healing. Do not damage trees unnecessarily during harvest and minimize winter damage. Prune and remove affected tree areas to minimize chances of spread.