Aspen shoot and leaf blight
Aspen shoot and leaf blight is caused by the pathogen Venturia macularis, which occurs primarily on trembling aspen (Populus tremuloides) throughout British Columbia. New infections occur in the spring during bud break and leaf expansion.
Venturia macularis causes shoot blight which stops the growth and causes deformities in terminal shoots, resulting in a shepard’s crook. Leaf spots also occur, and these spots expand and merge, covering the entire leaf, which wilts.
V. macularis can kill most shoots in trembling aspen stands that regenerate by sprouting. Repeated infections cause a reduction in growth. This disease is most severe in young stands, and has the greatest impact in intensively managed plantations. Repeated infection may result in small and stunted deformed crowns. Periods of mild wet spring weather are conducive to epidemics, but the disease abates with the arrival of hot and sunny summer days. The damage is most commonly reported from the Northeast, Omineca and Skeena regions.
In managed plantations or poplar stool beds it can be possible to reduce the magnitude and spread of the disease by removing and destroying the leaves that drop to the ground in the fall.