CANE DISEASES OF BRAMBLES Leptosphaeria coniothyrium, Elsinoe veneta, and Didymella applanata   F A C T S H E E T

Introduction

Several fungi commonly cause cane diseases on brambles.

CANE BLIGHT is caused by the fungus Leptosphaeria coniothyrium. Although cane blight may occur on all brambles it is most common on black raspberry.

ANTHRACNOSE is sometimes called cane spot, this disease is caused by the fungus Elsinoe veneta. Anthracnose is a serious disease of purple and black raspberries. The anthracnose fungus may also infect blackberries. Red raspberries, however, are not seriously affected by this disease.

SPUR BLIGHT is caused by the fungus Didymella applanata. Al1 raspberries can become diseased, but red raspberries are more prone to infection by the spur blight fungus than other brambles. Blackberries are not affected.

Figure 1: Cane Blight caused by Leptosphaeria coniothyrium (provided by the Plant Disease Diagnostic Clinic, Cornell University) Figure 2: Cane Blight caused by Leptosphaeria coniothyrium (provided by the Plant Disease Diagnostic Clinic, Cornell University)

Symptoms

CANE BLIGHT On new canes, symptoms often do not show up until late in the growing season. Dark brown cankers appear on the canes and are always associated with a wound, pruning cut, or stub (Figures 1 and 2). Fruiting canes that are infected produce weak growth and wilt as fruit begins to ripen. Dark brown cankers may be found on the canes below the weak or wilted growth.

SPUR BLIGHT shows up on new growth in mid to late summer as dark brown or purplish lesions around the buds. Infected buds slowly shrivel and the following spring produce weak shoots or may fail to grow altogether. By this time the brown or purplish lesions around the buds will appear ashy gray. Cracks and splits may form in the bark as the blight progresses.

Disease cycle

The CANE BLIGHT fungus produces spores in numerous tiny, black structures in the bark throughout the cankered areas. These structures release spores during wet weather from spring through summer. Spores may be spread by wind, splashing water and insects. Spores that land on pruning cuts, stubs, broken fruit stems, cracks in bark, or other wounds may be successful in causing new infections.

The ANTHRACNOSE fungus produces spores in tiny, black structures arranged in concentric ring patterns in the loose, grayish diseased bark. These structures release spores during wet weather beginning in early spring. The spread of spores to new growth is favored by rain, wind, and splashing irrigation water.

The SPUR BLIGHT fungus, Didymella applanata, produces spores in tiny, black structures in the diseased bark especially near the bud. These structures release spores during wet weather. The spores are spread by rain, wind, and irrigation water. Spores that land in the moist areas near buds on young canes may be successful in causing new infections.

Management Strategies

The same management practices may be used for spur blight, anthracnose, and cane blight. In March or April before new canes emerge, prune dead, diseased, or weak canes and destroy or trash them. Since these diseases are favored by moist conditions, keep the brambles properly spaced and pruned so they will dry quickly after rain or irrigation.

Red raspberry varieties that are most susceptible to spur blight include Royalty, Titan, Taylor, Canby, Skeena, Matsqui, Williamette, Reveille, and Sentry. Brandywine, Killarney, Latham, Madawaska, Festival, Hilton, and Newburg are less susceptible to the disease.

The most effective way to manage these diseases is with a lime sulfur. Apply according to label directions at bud break when no more than 1/2 inch of green is pushing out of the buds. Sprays applied after the green tips show 3/4" or more may burn the leaves.

Created, KLS, 8/99; Updated, SLJ, 1/05