Apple Crown Rot

Crown rot continues to be a major cause of tree death in Pennsylvania orchards. It is often observed on 3- to 8-year-old trees grown on Malling Merton (MM) 104, MM.106, M.7, and to a lesser degree MM.111 rootstocks. The disease is often observed in low-lying areas of orchards with heavy, poorly drained soils.

Symptoms
The first symptoms to appear in the spring are delayed bud break, leaf discoloration, and twig dieback. These symptoms indicate that crown infection is advanced. While infected trees may survive the growing season, they show symptoms of leaf and bark discoloration and premature leaf drop in the fall.

The most obvious symptom found on affected trees is a partial or complete girdling of the trunk. Close examination of the roots often reveals reddish brown, water-soaked areas of necrotic tissue located at the base of the root where it attaches to the rootstock. The entire underground portion of the stem is usually water-soaked and brown, and the necrotic area usually extends upward to the graft union.

For more information, please see Penn State Tree Fruit Production Guide.

Penn State Horticulture Department

For more information on this subject, Please visit the College of Agricultural Sciences Publications Web site.

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