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Black Rot

Black rot

Botryosphaeria obtusa

Authors: Kasia Kinzer and Joseph Zeleznik

Symptoms

• Small brown to tan, nearly circular spots with darker brown margins (frogeye leaf spot) appear on leaves.
• Dark brown, sunken cankers can form on branches and main stems. Leaves on cankered branches turn bright yellow and eventually die. Cankers can girdle and kill branches and stems.
• On fruit, lesions appear as reddish flecks and expand to blotches with a red halo, then, alternating brown and black rings (black rot). Affected fruit can shrivel and remain attached to the tree.

Black Rot

Figure 1. Frogeye leaf spot with distinctive purple margins (Esther McGinnis, NDSU)

 

Black Rot 2

Figure 2. Yellow arrows point to frogeye leaf spot and red arrows point to apple scab (Joseph Zeleznik, NDSU)

Figure 1Photo by Bergdahl, ND Forest Service

Figure 3. Frogeye leaf spot (Aaron Bergdahl, N.D. Forest Service)

Figure 2

Figure 4. Black rot symptoms on fruit (University of Georgia Plant Pathology, Bugwood.org)

Figure 3Photo by Zeleznik, NDSU

Figure 5. Yellowing leaves indicate a black rot canker (Joseph Zeleznik, NDSU)

Management and other important facts

• Remove and destroy mummified fruit and leaf debris to minimize infection the following year.
• Properly prune out infected branches and dead wood when trees are dormant. See “Basic Guidelines for Pruning Trees and Shrubs” (H1036).
• Fungicides are not recommended.

This website was supported by the U.S. Department of Agriculture’s (USDA) Agricultural Marketing Service through grant 14-SCBGP-ND-0038.
Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the USDA.

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