Brown Rot of Stone Fruits
Click for larger image Shriveled peach (Prunus) caused by brown rot

Brown rot in stone fruits such as apricots, cherries, nectarines, peaches, and plums is caused by Monilinia fructicola. Brown rot is the most destructive stone-fruit disease in the U.S.

Symptoms and Diagnosis

Plants infected with brown rot will develop brown, sunken cankers on the twigs; gummy sap will ooze out of these cankers. Infected twigs die. Young fruit will develop small, circular, brown spots. As the fruit develops, the spots enlarge and may cover the entire fruit. These spots can become covered with fuzzy gray spores after rainy weather. When infected fruit are sliced open, the flesh will be brown, dry, and firm. Fruit may either drop prematurely or remain in the tree past harvest time to brown completely and shrivel into mummified form.

Life Cycle

Fungal spores overwinter in twig cankers or the mummified fruit either on the ground or on the tree. With the help of the wind and rain, spores may infect healthy flower buds the next spring. After infecting the flowers, the fungus grows into the twigs. Moist weather encourages this growth into the twigs and gummy sap will ooze from lesions formed there. Spores will also develop on the lesions and infect the maturing fruit which are more susceptible than the younger fruit.

Integrated Pest Management Strategies

1. Prune infected twigs. Pick off rotted fruit. Clean up fallen fruit before and during harvest. Remove and destroy all unharvested fruit during the dormant period.

2. Apply fungicides at the proper time. The critical times to manage brown rot are the first three weeks after petal fall and the last three weeks before harvest. Pesticides registered for use include copper, captan, cyfluthrin, iprodione (Chipco), maneb, sulfur, thiophanate methyl (Cleary 3336), thiram, and ziram. Apply sulfur just before harvest.

3. Plant fruit tree varieties that are resistant to the disease:

Cherry: ‘Stark Gold’ or ‘Northstar Tart’.

Peach: ‘Carmen’, ‘Elberta’, or ‘Orange Cling’.

Organic Strategies

Strategies 1 and 3 are strictly organic approaches. Of the fungicides listed in Strategy 4, consult the Organic Materials Review Institute (OMRI™) for appropriate organic copper and sulfur products.

More images:

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Peaches (Prunus) covered with fuzzy gray spores of brown rot
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Brown rot on mummified peach (Prunus); note, gummy sap
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Leaf and stem of peach (Prunus) infected by brown rot
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Brown rot on peach (Prunus)
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Close-up of brown rot on peach (Prunus)
 
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