Pecan Scab

— Written By damaged pecans

Pecans are a tasty, popular food native to North America. They are enjoyed in many desserts, salads, or just by themselves. Unfortunately, many growers are experiencing low yields this year due to a powerful enemy known as pecan scab. This disease can destroy 50 – 100% of the crop depending on the amount of rainfall in the growing season, being more severe during wet years.

Pecan scab, caused by the fungus Cladosporium caryigenum, is generally the most damaging pecan disease. The disease can be identified by the following symptoms: They may be small, circular, or have olive-green to black spots form on the lower surface of the leaf and nuts. These spots may have a velvety or cracked appearance. Sometimes these spots combine forming large, irregularly shaped darkened areas. On nuts, these spots appear to be sunken. Infected foliage may prematurely drop. When infection is severe, the entire nut surface is black, development is arrested and the nut drops prematurely or fails to grow.

Prevention of pecan scab is possible. The first step is to choose tree varieties such as Mandan, Lipan, and Amling (excellent for homeowners) that offer some resistance to the disease. It is also important to remove debris such as leaves, shells and limbs in the fall and winter. It is possible to control the disease with chemicals; however, this typically requires special equipment to apply and may not be feasible or economical for homeowners.
Additional information is available at the following site:

Written By: Bonnie O’Neal: Master Gardener Intern