June 2015 Plant Disease Advisory

In the past few years, blossom blight, caused by the fungus Monilinia spp., has been observed in the spring on ornamental cherry (e.g. Kwanzan cherry) in the Mid-Atlantic region of the US. Infected blossoms turn brown and become stuck together in a gummy matrix (Figure 1). Gray to tan spore masses are produced on dead blossoms. The disease is favored by wet spring weather. 

Blighted blossoms on Kwanzan cherry.
Blighted blossoms on Kwanzan cherry.

Fungicide sprays must be applied before symptoms appear to avoid blighted blossoms. Fungicides labeled for use on ornamental landscape plants that contain the active ingredients chlorothalonil or propiconazole should be used, according to label directions, when blossoms open. Monilinia species also cause brown rot on stone fruit trees (i.e. plum, peach, cherry, apricot, nectarine). Brown rot is a devastating fruit rot disease that will be covered in a future Plant Disease Clinic update.