Here is a list of common raspberry pests and diseases and what you can do about them:
Spur blight, Cane blight, and Anthracnose:
These diseases cause various kinds of spotting (reddish blotches where leaves attached; large brownish purple areas; gray spots with reddish margins) that result in withered berries and death of leaves, side shoots, or canes. Control with pruning and good site selection so canes stay drier; do not prune canes when wet; if necessary, spray lime-sulfur in spring just as leaves emerge.
This disease, evidenced by bright orange pustules on the undersides of leaves, affects only black and purple raspberries; there is no cure so remove infected plants, including the roots, as soon as the disease appears to prevent spread from one plant to another.
A soil borne fungus that causes leaves to yellow, wilt, then die; there is no cure so avoid planting where other hosts of this disease, such as tomatoes, peppers, and eggplants, have grown recently; the most resistant raspberries are the reds and yellows.
This disease causes tumorous growths in plant crowns and root systems, and cannot be cured once a plant is infected. Avoid with healthy nursery stock and by inspecting the roots of new plants before you put them in the ground.
This disease, which covers the fruit with a light gray fuzz, is most prevalent in wet weather; avoid it with good site selection and pruning for air circulation, by picking and discarding infected berries, and by harvesting often.
Phytophthera root rot:
Most prevalent on red raspberries although Killarney and Boyne are somewhat resistant; avoid this disease by starting with pest-free plants and planting them in well-drained soil
Look for the tell-tale wilting of canes beginning above where these insects do their boring; the cane may also be swollen where insect entered and have a series of puncture holes; prune out and destroy infected canes as soon as you notice them.
Raspberry crown borer:
This insect causes whole canes to die or break off easily; dig out and destroy infected plants; vigorously growing plants are less likely to be attacked.
These small, spider-like creatures cause white speckles, then discolored blotches, to develop; look closely to see their silken threads; control by keeping soil moist and, if necessary, spraying insecticidal soap or lime sulfur.