Peach canker is a fungus disease common on apricot, prune, plum, and sweet cherry trees as well as on peach trees. The disease is common in peach orchards and is a frequent cause of limb dying and death of peach trees. Other common names for peach canker are perennial canker and Valsa canker. The fungi that cause this disease enter the plant through wounds. Infection results in dead and weakened twigs and branches, and in reduced yields.
The first symptoms appear in early spring as gummy drops of sap around wounded bark. The diseased inner bark begins to break down, causing the cankered surface to appear depressed. Black specks, which are fungal spore producing bodies, appear on the bark surface or under the bark tissue. During wet periods spores ooze out of these fungal bodies in tiny orange or amber colored, curled strands. During the summer, healthy bark (callus tissue) grows over the edges of the narrow, oval shaped cankers. In the fall, the fungus resumes growth, attacking and killing the new callus tissue. Over a period of years, a series of dead callus ridges form as the canker gets larger. Eventually, the canker may completely surround a branch. The portion of the branch beyond the canker then dies. Large amounts of gum are usually produced around cankered areas. Peach canker is often confused with other problems which cause cankering and gumming. Among these are bacterial canker, insect borer injury and mechanical injury. When insects are involved, chewed-up wood dust is usually visible under the gum. Mechanical injury can often be verified by carefully reviewing recent operations in the area.
Peach canker is caused by the fungi, Cytospora leucostoma and Cytospora cincta. These fungi are weak pathogens and generally do not attack healthy, vigorous peach bark. Winter injury, insect damage, and mechanical injury are common types of wounds serving as entry points. The fungi survive the winter in cankers or in dead wood. During spring and summer, spores produced in the cankers are spread by wind and rain to wounds on the same or nearby trees. The spores are not blown over long distances in the wind. Infection and canker development depend on temperature and the species of fungus involved. Cytospora cincta is favored by lower temperatures than Cytospora leucostoma. Because of the manner of infection and development of this disease, no single control measure is adequate. Most known control methods act indirectly by reducing points of entry or by reducing the level of inoculum. Fungicides are generally ineffective for controlling this disease.
For the most current spray recommendations, commercial growers are referred to Bulletin 506-A2 "Ohio Commercial Tree Fruit Spray Guide," and backyard growers are referred to Bulletin 780 "Controlling Diseases and Insects in Home Fruit Plantings." These publications can be obtained from your county Extension agent or the Extension Publications Office, The Ohio State University, 385 Kottman Hall, 2021 Coffey Road, Columbus, Ohio 43210-1044.
Click here for a PDF version of this Fact Sheet.
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868