Trembling aspen, Swedish columnar aspen, tower poplar
Distribution and Disease Cycle
Symptoms typically appear in midsummer. Spores are dispersed from April-June when rainfall is present and temperatures are around 18ºC. Once infected, the fungus moves systemically within the leaf's vascular system, making it difficult to control.
Symptoms and Signs
Leaf margins develop yellow, orange or reddish brown discolourations, which expand to consume the entire leaf. Often veins remain green while the remaining leaf tissue becomes discoloured. Depending on the host, all leaves on a singly shoot may exhibit symptoms of the disease or symptomatic leaves may be scattered throughout the crown of the tree. Eventually, leaves develop a bronze or dark reddish-brown hue, often remaining attached to the tree, rather than abscising in fall. As the disease progresses, the fungus will infect the stem and cause dieback after several seasons of infection.
Remove and destroy fallen leaves if possible. Prune to remove dead branches and increase air circulation; avoid dense plantings that can reduce air flow. Avoid using monocultures of susceptible species in mass plantings or shelterbelts which can accelerate disease spread.