Disease Descriptions and Management
The diseases discussed below are common to all brambles; however, susceptibility to these diseases varies within the bramble groups. See basic cultural guidelines for the control of plant diseases under Pest Management. Table 2.4 lists pesticides available for the control of diseases on various fruit crops. Pictures of fruit diseases can be found in the Fruit Pathology Fact Sheets.
Anthracnose, commonly called "cane spot" or "gray bark," occurs in several species of Rubus. It is considered an extremely serious disease of black, purple, and susceptible varieties of red raspberry. Severe yield loss can result due to defoliation, wilting of lateral shoots, death of fruiting canes, and reduction in fruit size and quality.
Botrytis fruit rot or gray mold is the most common and most serious disease of Rubus species worldwide.
Cane blight usually affects only canes that have been wounded in their vegetative year. It sporadically attacks canes of all Rubus species. Black raspberry is more susceptible to this disease than the other brambles.
Crown and cane gall are bacterial diseases that seriously limit raspberry production in Pennsylvania. Crown gall is the more widespread of the two diseases and affects all brambles as well as apples, grapes, peaches, and roses.
Orange rust is a fungal disease that occurs only on brambles, particularly blackberries, dewberries, and black raspberries.
Late leaf rust can be a problem on fall-bearing raspberries.
Phytophthora root rot is now regarded as a major cause of declining red raspberry plantings. Blackberries and black raspberries appear to be less susceptible than red or purple raspberries.
Blackberries are seldom severely infected by powdery mildew. It is occasionally a serious problem on susceptible varieties of red and black raspberries, especially the Black Hawk and Latham varieties. Infected plants may be stunted and less productive.
Red and purple raspberries are more affected by spur blight than black raspberries. Blackberries appear to be immune.
Verticillium wilt is caused by two common soilborne fungi. These fungi have a wide host range and attack more than 300 woody and herbaceous plants.
Virus diseases can seriously damage brambles, especially raspberries, and can affect the lifetime of a planting. Once the plant is infected with the virus, the entire plant will be infected for the remainder of its life.
Mosaic affects all raspberries but seldom affects blackberries. The mosaic virus complex overwinters in infected plants and is spread by aphids.
Raspberries are affected more severely by leaf curl than are blackberries. Many blackberry varieties remain symptomless when infected. Symptoms of infection by the leaf curl virus gave rise to the disease name.
Crumbly berry is the most common bramble virus in the Mid-Atlantic region. This is a red raspberry disease caused by the tomato ringspot virus and spread by the dagger nematode.
In the Mid-Atlantic region Tomato Ringspot Virus is vectored by dagger nematodes (Xiphinema spp.) and possibly pollen. This virus has a wide host range, including many weeds such as dandelion and chickweed.
Inconspicuous purple streaks less than 1 inch long form during warm periods on the lower part of infected canes. Infected plants usually are vigorous, sometimes with no symptoms of virus infection.
Control measures are aimed mainly at removing sources of the virus particles from within and around the raspberry planting.