Bacterial Spot on Stonefruit Trees

Need to Know

• Caused by the bacterial pathogen.
• Leaves develop small, angular, water-soaked spots at the tips, with the center of the spot falling out. 
• Bacterial spot survives in cankers and shoots over winter. 
• Find resistant peach cultivars, plant away from susceptible varieties. 

Overview of bacterial spot on stonefruit trees

Bacterial spot on fruit trees is caused by the bacterial pathogen Xanthomonas arboricola pv. pruni.

Symptoms of bacterial spot on stonefruit trees

Leaves develop small, angular, water-soaked spots at the tip, and the end of the leaf eventually turns brown or black. Centers of spots often fall out and are surrounded by a reddish margin. Severely infected leaves turn yellow and fall off.

Fruits become pitted or cracked if infected early in the season. Late-season infections are shallower, giving the fruit a mottled appearance.

Signs of bacterial spot on stonefruit trees

Bacterial ooze (streaming) may be evident when observed using a microscope. culturing and other testing are recommended to confirm this problem as symptoms may resemble other diseases.

Disease cycle of bacterial spot on stonefruit trees

The bacterium that causes bacterial spot survives the winter in cankers on shoots. In spring, bacteria ooze out of the cankers and are spread by windblown rain to leaves, fruit, and shoots.

Type of Sample Needed for Diagnosis and Confirmation of bacterial spot on stonefruit trees

The Iowa State University Plant & Insect Diagnostic Clinic can help you investigate and confirm if your plant has this disease. Please see our website for current forms, fees, and instructions on collecting and packing samples. Contact information for each state's 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.

Want to submit a sample? Follow the instructions leaf spot section at Submitting Trees and Shrubs page. 

Management of bacterial spot on stonefruit trees

Several peach varieties with fairly good resistance are available. Consult the local extension office or garden center, and check nursery catalogs for resistant varieties. This is the best control option for peaches. Most apricot and nectarine varieties are susceptible.

If possible, locate new plantings away from older ones containing susceptible varieties.

Use a balanced fertilization program. Over-or under-fertilized trees are more vulnerable to bacterial spot.

 

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.