University of Maryland Extension

Brown Rot on Ornamental Cherries - Trees

diseased leaves and twigs

Back to Common Problems - Trees and Shrubs

Spring weather often brings with it the chances of diseases in our landscapes and unfortunately the past few springs have brought a serious disease to our flowering cherries, especially the cultivar ‘Kwansan”.  This new disease is really an old orchard disease of stone fruit called brown rot.  In Maryland landscapes, this new problem is caused by the fungus Monilinia laxa

The first symptoms often seen are browning and collapse of the blossoms followed closely by death of the small twigs.  The symptoms look like fire blight, but cherries are not susceptible to that disease.  If infected blossoms do not drop off, the fungus may grow through the flower stem (pedicel) and into the twig below. Twigs develop elliptical cankers with profuse gumming at the margin between diseased and healthy tissue. Leaves on these infected shoots turn brown and wither, but remain attached. In some instances, twigs are girdled and killed. During wet weather in May and June, the fungus sporulates on the surface of infected twig cankers. Cankers enlarge from season to season, and sporulation may continue on large cankers for 4 years or more.

brown rot on Kwansan

Visible presence of the pathogen is easy under wet conditions and appears as powdery tufts of brown-gray spores that are visible on the outside of infected flowers and on infected fruit or twig surfaces.

Management of this disease in orchards relies on good sanitation and proper timing of protectant fungicides.  However, in ornamentals this disease is a new problem and has not been studied extensively.

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