Leaf and Shoot Blight (Venturia macularis, V. populina V. tremulae)

From: Ostry, Michael E.; Wilson, Louis F.; McNabb, Harold S., Jr.; Moore, Lincoln M. 1988. A guide to insect, disease, and animal pests of poplars. Agric. Handb. 677. Washington, DC: U.S. Department of Agriculture. 118 p.

Importance- The disease is usually most severe in young aspen stands, but it can also affect hybrid poplars. Affected stems and leaves become blackened and distorted. Death of terminal and lateral shoots can distort small trees, causing a shrubby tree form and reducing growth. After repeated attacks, small trees may die because of suppression and infection by other disease organisms.

Look For: Irregular, brown to black areas on leaves in early spring. Black, brittle shoots that are curled to resemble a shepherd's crook. Olive-green appearance of recently infected tissues caused by the layer of spores (conidia) produced.

Leaf Blotches.

Biology- Primary infections are predominantly caused by conidia produced from mycelium in shoots killed the previous season. Infection can also result from ascospores that develop in leaves on the ground that were killed the previous season. Conida are rainsplashed to new shoots and leaves, causing secondary infections that rapidly multiply. Trees growing in dense stands are often more severely diseased than those growing at wider spacings. Only young shoots and leaves are susceptible. Later in the season, as these tissues mature, they become resistant.

Control: Direct control is usually not needed. Disease severity differs among hybrids, so plant resistant clones.
Diseased Shoot	Conidia.

For Additional Information:

Anderson, N. A.; Anderson, R. L. 1980. Leaf and shoot blight of aspen caused by Venturia macularis in northern Minnesota. Plant Disease. 64: 558-559.

Dance, B. W. 1961. Leaf and shoot blight of poplars (Section Tacamahaca Spach) caused by Venturia populina (Vuill.) Fabric. Canadian Journal of Botany. 39: 875-890.

Ostry, Michael E. 1980. How to identify shoot blight of poplars. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station. 5 p.