University of Maryland Extension

Fungal Leaf Spots - Shrubs

leaf spots on mountain laurel

Leaf spots caused by fungi often can be distinguished by their fruiting structures and pattern of lesion development. There are numerous leaf spotting diseases that occur on shrubs, but few are lethal. Most established shrubs produce more leaves than they need for normal growth. Unless severe leaf defoliation takes place, enough leaves are usually left for healthy growth. On young shrubs or newly planted shrubs leaf loss is more detrimental. When a shrub loses most of its leaves its food reserves are depleted which may cause dieback, decline, and/or death. The majority of leaf spotting diseases are favored by cool, wet, spring weather. Shrubs that are prone to leaf spotting diseases include aucuba, mountain laurel, photinia, roses (cercospora and black spot), junipers, firethorn, leucothoe, and rhododendron.

leaf spot leucothoe
A leaf spot disease on Leucothoe

Management strategies

In most cases, leaf spotting diseases will not threaten the health of the shrub. The best management practices for most leaf spotting diseases involve pruning and removal of infected leaves and dead twigs during the winter or dry summer months. Mature shrubs can be thinned for better air circulation. Rake and remove infected fallen leaves in the fall and plant resistant varieties when available. For plants such as roses, where leaf spots can be detrimental, select resistant cultivars and apply fungicides when necessary.

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