Anthracnose, caused by Elsinoe veneta, is a common fungal disease of brambles. It is mainly a problem on black raspberries and some blackberries. It is much less common on red raspberries. Most modern thornless blackberries (Apache, Triple Crown, Osage, Ouachita, etc) are resistant to anthracnose. However, if you grow a susceptible variety, is is important to control this disease. Damage to canes and leaves can reduce vigor and fruit size, and fruit infections are possible. A single application of fungicide is effective at controlling anthracnose, but timing is critical. It must be applied just as the shoots are beginning to grow. Normally we recommend applications at 1/2 to 3/4 inch shoots.
The time for applications is upon us! Brambles have budded out early this year and are at the appropriate stage for treatment now. Apply liquid lime sulfur, Sulforix, or copper hydroxide according to label recommendations. Lime sulfur or Sulforix may burn the leaves if they are beyond 1 inch long, especially on hot, sunny days. If your crop has advanced too far, you may want to apply the lowest recommended rate, or apply on a cool, cloudy day or late in the evening. Copper hydroxide is less likely to cause leaf burning.