Aspen Leaf Diseases Responsible For Thin Crowns

By Linda Williams, Forest Health Specialist, Woodruff, or 920-360-0665

Northeastern Wisconsin saw thin and defoliated aspen trees in early summer this year due to a few diseases. A sample from Marinette County turned up Alternaria leaf and stem blight, Venturia leaf and shoot blight and Phyllosticta leaf spot. Venturia was also noted in central Wisconsin, causing shoot blight, which kills the terminal leaders (growth buds) of young aspen.

Aspen trees with leaves damaged by leaf disease..

Aspen crowns were thin due to multiple leaf diseases. Photo: Wisconsin DNR

Severe leaf infections were noted in several counties, but symptoms have become less obvious throughout summer. Aspen trees sent out additional leaves mid-summer, which were not infected, so crowns have filled out more.

Terminal leader of a young aspen is black and curled due to Venturia shoot blight.

Venturia shoot blight can kill the terminal leader of young aspen. Photo: Wisconsin DNR

No control is recommended for forests. Young aspen with terminal leaders killed by shoot blight will put out new growth the following year. Aspen in urban settings are more rare, but cleaning up fallen leaves in autumn can help reduce disease.

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