Shoot blight of aspen

 

Shoot blight of aspen

A widely distributed disease affecting zero to five- year old aspen causes death, blackening, and drooping or curling of terminal leaves and shoots. A fungus, Venturia macularis, overwinters as both spores and mycelium (threadlike network of fungal cells) in infected leaves and shoots. This disease is of little or no economic importance in natural stands, although repeated loss of current growth can result in stag-headed trees and thus delay harvest. Damage to hybrids in plantations can be serious. In the spring, the overwintered spores cause the primary infection. Spores produced after this cause secondary infection on the older leaves. Infection increases rapidly during wet springs but subsides with the onset of warm, dry, summer days.

Control in yard trees involves removing fallen infected leaves and shoots in the autumn and early spring. Pruning to remove any overwintering stage on infected shoots also checks the spread of the disease. Fungicides used at bud break have also proven effective as a control measure.