Leaf and shoot blight of aspen (Venturia macularis)

Leaf and shoot blight of aspen (<em>Venturia macularis</em>) - Necrotic shoots and leaves on aspen caused by <em>Venturia macularis</em>. Note characteristic

Latin name: Venturia macularis (Fr.:Fr.) E. Müller & Arx
French name: Brûlure des pousses à Venturia macularis
Division: Ascomycota
Class: Pleosporales
Synonym(s): Didymosphaeria populifolia Ellis & Everh.,
Mycosphaerella macularis (Fr.:Fr.) J. Schröt. in Cohn,
Mycosphaerella orbicularis (Peck) House,
Phaeosphaerella macularis (Fr.) Trav.,
Spilocaea tremulae (Frank) Sacc.

Description

Micro-habitat(s)

Leaf, Branch, Seedling, Annual shoot

Distribution

Canada

Damage, symptoms and biology

The pathogen causes shoot blight, stopping the growth and causing deformities in terminal shoots. Angular blackish spots on the foliage are the earliest symptoms of the disease. These spots expand and merge, covering the entire leaf, which wilts. The affected part, which still bears leaves, elongates and droops. In the spring, new leaves become infected by spores present in the leaf litter. During very wet weather, particularly in the spring, an olive-green exudate can be seen, which contains the spores.

When wet weather conditions prevail during the growing season, 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.

Other information

The spread of the disease is favoured by cool, wet spring weather, but the disease abates with the arrival of hot and sunny summer days. Removing and destroying the leaves that drop in the fall helps to reduce the magnitude and spread of the disease.

Pollaccia radiosa is the asexual stage (anamorph) of Venturia macularis.