General Information.  Anthracnose is a fungal disease most common in wetter fruit producing areas west of the Cascades. The disease is occasionally encountered in higher valleys east of the Cascades. Anthracnose was first reported in 1900 and has since been found in Nebraska, Idaho, California, Massachussetts, Maine, Michigan, Illinois, British Columbia, Denmark, Holland, and New Zealand. Cankers rarely kill trees because most cankers occur on small twigs and branches. However, the cankers serve as an inoculum source for a fruit rot known as bull's eye rot. The fruit rot does not usually appear until the fruit is in CA storage. Anthracnose is etiologically similar to perennial canker. Perennial canker, a similar disease caused by a closely related organism, is generally more prevalent on the eastern side of the Cascades.

Symptoms.  New anthracnose cankers appear as small, circular spots that are red or purple when moist. As they enlarge, they become elliptical, sunken, orange to brown areas in the bark. A crack eventually develops between the diseased and healthy tissue. Erumpent, cream-colored acervuli appear through cracks in the periderm. The bark sloughs off older cankers, exposing the wood beneath, or disintegrates, exposing longitudinal bast fibers, which give cankers a characteristic fiddle-string appearance. Anthracnose cankers rarely enlarge after the first year.

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Bull's eye rot is a postharvest disease that is usually observed when infected fruit are removed from storage.  The disease gets its name from the lesions that frequently are comprised of concentric rings of necrotic tissue.  Cream colored tufts of spores are sometimes present.  Infection occurs in the orchard around petal fall or just before harvest.

Epidemiology.   The fungus survives as mycelium and conidia in branch cankers. New cankers appear in fall and enlarge the following spring, reaching full size in May. Acervuli first appear during late summer and fall about a year after infection. The cankers do not expand after the first year, but the anthracnose fungus can sporulate on the dead bark for several years. Sporulation occurs during cool, moist weather. Conidia are exuded in a gelatinous matrix and splashed to wound cites by rain. The fungus penetrates the bark directly.

Management.   Canker removal is recommended because it destroys the inoculum source required for new canker development and bull's eye rot. A dormant spray of Bordeaux mixture, followed by a Bordeaux application, captain, ziram, or fixed copper prior to autumn rains, is recommended for anthracnose canker control. Spartan, Gravenstein, Chehalis, and Baldwin are highly susceptible to anthracnose.

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Last Update: 12/21/04
 Web Author: Dr. Gary Grove
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