Brown Rot on Ornamental Cherries - Trees

Brown rot infected leaves of a cherry tree

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 the collapse of the blossoms followed closely by the 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.

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

This is a common disease found in fruit orchards and management relies on good sanitation and proper timing of protectant fungicides. However, in ornamentals, this disease is a new problem and the control has not been studied extensively.