Bramble (blackberry and raspberry) Anthracnose (Elsinoe veneta)
Bruce Bordelon, Professor, Horticulture & Landscape Architecture, Purdue University
Anthracnose is a common and widespread disease of brambles. It can infect red, black, and purple raspberries, blackberries, dewberries and loganberries. The disease is very destructive on black and purple raspberries. Red raspberries tend to be more resistant to this disease.
Anthracnose can cause symptoms on canes, leaves, fruit, and berry stems. The most striking symptoms are on the canes. A few days after the fungus invades the succulent tissue of young primocanes, minute purplish spots appear. These spots enlarge in diameter and become oval shaped. The centers become somewhat sunken and are pale buff to ash gray in color. Margins tend to be purple to brown. When numerous, lesions may merge and cover large portions of the cane, often causing girdling. By the end of the season, the tissue in the lesions become dry and crack. These lesions are very noticeable the next season during pruning (Picture 1). Severely infected canes should be pruned out if practical. Fruit produced on severely infected canes may fail to develop normal size and may shrivel and dry, especially in a dry growing season. Severely infected canes often lack winter hardiness and may die during a harsh winter.
Control of anthracnose in brambles can be relatively easy. The use of fungicides and cultural practices such as sanitation (removal of old and infected canes) are key control methods. When the disease is a problem, the best control is a delayed-dormant application of liquid lime sulfur or Sulforix (calcium polysulfide). This fungicide effectively kills the developing spores (primary inoculum) at the beginning of the season and prevents the disease from becoming established. If this spray is missed and the disease becomes established, control is much more difficult. Lime sulfur will burn tender foliage so it must be applied just as new growth begins, but before the leaves are exposed more than ½ to ¾ inch (Picture 2). The single application of lime sulfur usually provides nearly complete control. That’s why it’s important for growers with a significant problem last season to plan for an early season fungicide application this year.
Click image to enlarge
Picture 1. Lesions on black raspberry
Picture 2. Apply lime sulfur just as new growth begins