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 SOOTY BLOTCH ON APPLES

AUBURN, APRIL 28, 2000---Sooty blotch is one of the most common diseases of apples in the Southeast. The
fungi causing the disease affect all apple cultivars.

Sooty blotch fungi only grow on the surface of the fruit, giving it an unsightly appearance. The fungal colonies are
olive green to black on mature fruit. Colonies can be round or feathery, have diffuse margins and cover the entire
fruit, says Edward Sikora, Extension plant pathologist with the Alabama Cooperative Extension System.

The complex of fungi that cause sooty blotch grows on the waxy cuticle of the apple fruit. These fungi survive from
one season to the next on apple twigs as well as on other perennial vegetables that have a waxy cuticle. The fungi
are spread by wind and in windblown rainwater to developing fruit in the spring and early summer. Secondary
spread occurs from initial sites throughout the summer. 

The optimum temperature for growth is between 65 and 80 F, and it usually takes 20 to 25 days after infection for
the symptoms to appear on the fruit.

Control of sooty blotch is achieved through dormant and summer pruning and tree training that opens trees and
facilitates drying of the fruit. Fungicides need to be applied on a preventative basis beginning the second time the
fungi cover the fruit and continuing at 10- to 14-day intervals until harvest. 

For a list of recommended fungicides and spray schedules, see Extension publication ANR-500A, Alabama Pest
Management Handbook-Volume I, at your county Extension office. 

SOURCE: Edward J. Sikora, Extension Plant Pathologist, Alabama Cooperative Extension System, (334) 844-5502