PPDL Picture of the Week
August 1, 2016
Gail Ruhl, Senior Plant Disease Diagnostician, Purdue University
Brown rot, caused by the fungus Monilinia fructicola, is a common and destructive disease of peach and other stone fruits (plum, nectarine, apricot and cherry). The brown rot fungus may attack blossoms, fruit, spurs (flower and fruit-bearing twigs) and small branches. When the fungus invades shoots or twigs, it girdles stems and causes them to wither and die.
The symptoms of brown rot are very similar on all stone fruit. Wilted, brown flowers first appear during bloom, however the most noticeable symptom is the rotting fruit with light brown powdery tufts of fungal spores. Fruit infection may spread rapidly, especially when wet weather occurs during the fruit ripening period and when fruits are touching one another. The entire fruit rots rapidly, then dries and shrinks into a wrinkled "mummy." Rotted fruit and mummies may remain on the tree or fall to the ground.
A combination of both cultural and chemical control measures is required for control of brown rot. Since the brown rot fungus overwinters in infected twigs or in mummified fruit on the tree or on the ground, it is important to remove rotten fruit and mummies from trees after harvest and prune out cankered branches during the dormant season. Check the surrounding landscape and remove wild or neglected stone fruit trees that may serve as reservoirs for the disease. In addition, control of insects that feed on fruit is also essential. Anything that causes wounding of the fruit will increase the incidence of brown rot.
The use of fungicide is an important part of the disease management program for brown rot. The most critical time for control of brown rot is during bloom and just prior to harvest. A low risk spray program requires at least two to three fungicide applications during bloom and two to three shortly before harvest.