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Agricultural Research Service

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Lesions caused by pecan scab disease

New Money-Saving Strategies for Controlling Pecan Scab

By Tara Weaver
August 12, 1998

Pecan growers could save as much as $18 an acre in pecan scab control costs and cut chemical use by eliminating or delaying the typical first spray, according to Agricultural Research Service scientists.

Current scab control strategies often require nine to 11 fungicide sprays per season. Growers typically begin spraying as leaves emerge from swelling buds around the first or second week in April. ARS scientists found that these newly emerging leaves are not vulnerable to scab; foliage only becomes susceptible after the leaves have grown for about 10 to 14 days.

Pecan scab, caused by the fungus Cladosporium caryigenum, is generally the most damaging pecan disease. It causes lesions to appear on leaves as small, concentric circles, charcoal gray to black in color. Severe infection causes defoliation, fruit abortions and smaller, poorly filled fruit, reducing crop yields. It is active throughout the growing season, and if unchecked, can cause near total crop losses.

The disease is particularly troublesome for commercial pecan varieties--Desirable, Schley, and Stuart--grown in the Carolinas, Georgia, Alabama, Florida, Mississippi, Louisiana and east Texas, where the climate is generally moist. Overall, the disease costs pecan growers at least $22 million each year in losses and control costs.

Detailed information on this research appears in the August issue of Agricultural Research magazine. The story is also on the World Wide Web at:


Scientific Contact: Bruce W. Wood and Charles C. Reilly, USDA-ARS Southeastern Fruit and Tree Nut Research Laboratory, P.O. Box 87, Byron, Ga. Phone (912) 956-6420, fax (912) 956-2929,,

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