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 cultivars of red raspberry. Severe yield loss may result due to defoliation, wilting of lateral shoots, death of fruiting canes, and reduction in fruit size and quality.
Gray mold or Botrytis fruit rot is the most common and most serious disease of the Rubus species worldwide and is usually found on overripe and bruised fruit. The pathogen has a wide host range and overwinters in dead leaves and plant debris. The fungus rots fruit in the field before harvest, especially if rain occurs during blossoming. Most overripe and bruised fruit are susceptible, especially red raspberries. Aging leaves are also attacked, giving rise to cane infections.
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 including apples, grapes, peaches, and roses. Only grasslike plants seem to be immune to crown gall.
Orange rust is a fungal disease that occurs only on brambles, particularly blackberries, dewberries, and black raspberries. This disease is not known to affect red or purple 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. Wet soil conditions favor the development of the disease and it can often be observed in low-lying areas of a field. Declining plants previously diagnosed as suffering from "wet feet" or winter injury are usually infected by this root rot.
Brambles are seldom severely infected by powdery mildew. Occasionally, it is a serious problem on susceptible cultivars of red and black raspberries, especially the varieties Latham and Black Hawk. Infected plants may be stunted and less productive
Virus diseases can seriously damage brambles, especially the raspberry, 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. Virus infections cause decreased productivity, so it is important to start a planting with healthy plant stock obtained from a reputable nursery.