Stone fruit brown rot

Need to know: 

• Causes fruit rot, but the pathogen can also infect other plant parts. 
• Infected blossoms wilt, turn brown, and persist into the summer. 
• Infects cherry, apricot, peach, nectarine, and plum. 
• Optimal conditions are warm, wet weather.  
• Manage by scouting for disease, sanitation, and practicing plant health maintenance. 
• A fungicide spray program may help reduce fruit loss. 

Overview 

Brown rot is a common disease of stone fruit trees (Prunus sp) that affects the quality of the fruit.  Apricots are most susceptible, follow by nectarines, plums and cherry trees.  This fungal disease causes fruit rot, but the pathogen can also infect other plant parts. This article provides detail on prevention and management of this disease.

Symptoms of stone fruit brown rot    

Symptoms are commonly noted in the fruit, but can also 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. Tannish gray spore tufts break through the fruit skin, giving it a fuzzy appearance (signs). Infected fruit continues to rot after harvest, turning into black shriveled "mummies," some of which remain on the tree over winter.

Signs of stone fruit brown rot

Greyish-tan spores can be seen on rotted areas of fruit.

Disease cycle 

The fungus that causes brown rot, Monilinia fructicola, infects cherry apricot, peach, nectarine, and plum.Fruit losses are worst when wet, warm weather persists during the ripening period. Injured fruit is more susceptible to infection. Therefore care should be taken to minimize physical wounding during the growing season, especially at harvest. The brown rot fungus overwinters in mummies on the tree or the ground and dead twig tissue

Type of Sample Needed for Diagnosis and Confirmation 

The Iowa State University Plant & Insect Diagnostic Clinic can help you to investigate and confirm if you plant has this disease. Please see our website for current forms, fees, and instructions on collecting and packing samples. Contact information for each states diagnostic laboratory for U.S. residents.  If your sample is from outside of Iowa, please do not submit it to the Plant & Insect Diagnostic Clinic without contacting us

Management 

Plant health maintenance

One of the best ways to prevent the development of tree fruit disease is to maintain sufficient air circulation, which involves pruning to avoid overcrowding and proper plant spacing when planting. This will help to minimize the moisture retained in plant and effectively reducing the ability of the spores to germinate and infect.  

Scouting for disease 

Symptoms can be first observed as water-soaking or browning lesions on fruit and other plant parts. Keep an eye for symptoms starting, be especially vigilant when plants are flowering, and fruits are developing.

Sanitation

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, this is known as sanitation. Prune all cankers and blighted twigs during the dormant season. Prune trees annually to increase air flow. Remove and burn or bury all wild and neglected stone fruit trees. 

Chemical management

A fungicide spray program, beginning at bloom and continuing throughout the season, may help to reduce fruit losses caused by brown rot. Remember read fungicide labels and follow instructions.

Fungicide applications may be avoided by following good Integrated Pest Management practices like those listed in this encyclopedia article. Often, the only preventative application is effective to manage plant diseases. If the problem requires a fungicide, state law requires the user to read and follow all labels accordingly. For more information, read Proper fungicide use.