The fungus overwinters in infected canes. In the spring, spores are carried by wind and rain with infections occurring during periods of prolonged wet weather. Phomopsis spores infect tender young shoots. The fungus infects the trunk or a main branch, resulting in the formation of a canker. Each year the canker enlarges until it eventually girdles the trunk or branch, and killing the distal portion.
New shoots developing near the canker are weak and stunted.
These may result in failure of the vine to leaf-out or in the formation of dwarfed, yellowish, crinkled leaves. Infected canes which survive through the summer often die during the following winter. Eutypa dieback is caused by the fungus Eutypa armeniacae . The fungus overwinters in infected canes and through spores carried by wind and rain, infect grapevines during wet weather through wounds caused by pruning or winter injury. Prune and destroy diseased portions of the vines.