Branches may eventually die as old needles drop and no new growth survives. Look for these at the base of the needles under the sheath, on cone scales and on twigs. In wet weather, dark spore tendrils are exuded from pycnidia and spread by splashing rain, insects, birds or on tools. Spores are produced from early spring through late fall, in wet weather. Only young needles, buds and shoots are susceptible.
Mature tissues are resistant.
Thus, rainy spring weather is favorable for disease development. The fungus grows rapidly through needles and into the shoots. Blight symptoms are usually noticed by mid-summer. Needles and then entire shoots turn brown. The fungus persists from year to year in infected cones, needles and twigs on the tree and on the ground.