Poplar Leaf and Shoot Blight
Poplar leaf and shoot blight is caused by the pathogen Venturia populina, which occurs on black cottonwood (Populus trichocarpa), balsam poplar (P. balsamifera) and many hybrid poplars), throughout British Columbia. New infections occur in the spring during bud break and leaf expansion.
Dead shoots and black leaf spots become apparent in susceptible trees by mid-June in damp coastal regions. Secondary outbreaks may occur in the summer and fall following wet periods. When infection is severe, the new growth of a tree can look burnt. The disease overwinters as cankers on twigs, and in the spring the spores released from these cankers infect trees during bud break and leaf expansion.
Usually a complete stand is damaged, especially along river valleys. The most important damage done by this disease is to seedlings and saplings which may die-back severely, creating restocking problems. The damage is most commonly reported in the Northeast, Omineca and Skeena regions. The disease occurs infrequently but it can be severe in the Cariboo and Kootenay Boundary regions. There have been minor reports of the disease in the Thompson Okanagan, and the South and West Coast regions.
It is possible to reduce the magnitude and spread of poplar leaf and shoot blight in managed plantations or poplar stool beds by removing and destroying the leaves of infected trees that drop to the ground in the fall. Pruning out the overwintering cankers on twigs is the best form of control for nursery stock or landscape trees.