Cherry samples showing brown rot on the fruit have been arriving in the Plant Disease Clinic. Under wet conditions, light brown tufts of fungal spores form on the fruit, destroying the fruit rather quickly. Fruit losses are worst when wet, warm weather persists during the ripening period. Injured fruit are particularly susceptible to infection. Diseased fruit may fall to the ground or remain on the tree as mummies (dried shriveled fruit).
The fungus that causes brown rot, Monilinia fructicola, may also infect apricot, peach, nectarine, and plum. In addition to fruit rot, symptoms may occur on blossoms, spurs, and shoots. Infected blossoms wilt, turn brown, and persist into summer. The fungus may invade shoots or twigs, causing them to wither and die
The brown rot fungus overwinters in mummies on the tree or on the ground and in dead twig tissue. Removing fruit, mummies, and dead twigs from trees after the final harvest reduces the amount of brown rot fungus present at the beginning of the next season. Since injured fruit are more susceptible to infection, care should be taken to minimize physical wounding during the growing season, especially at harvest. To reduce the spread of the fungus on fruit after harvest, refrigerate fruit promptly after picking. A fungicide spray program, beginning at bloom and continuing throughout the season, will sharply reduce fruit losses caused by brown rot.
Brown rot and other common disease and insect problems of tree fruits are pictured and discussed in IDEA 2 Tree Fruits - Insect and Disease Management for Backyard Fruit Growers in the Midwest. This 41 page booklet is available for a small fee at any county extension office or from the Extension Distribution Center, 119 Printing and Publications Building, Iowa State University, Ames, Iowa 50011-3171, Telephone: (515) 294-5247, Fax: (515) 294-2945.
This article originally appeared in the July 2, 1999 issue, p. 89.