Q: My Dorman Red raspberries appear to have some sort of disease. These spots started after fruiting in June and just about wiped out the fruiting canes. Now all the new leaves on the new canes are starting to get the same spots. Any thoughts?

A: The disease is raspberry anthracnose. It’s a direct result of the rainy April and May we had this year. You didn’t notice them but there were lots of small purple spots on the canes. As they matured, the fungus infected the raspberry leaves.

Since the anthracnose fungus needs water to infect the plant, anything that promote rapid drying of your plants is good. Avoid overhead irrigation and make sure there is good airflow around your bed.

Prune out diseased canes each fall. You may even have to cut everything to the ground.

Spray liquid lime sulfur when the plants are breaking dormancy; after the leaf buds open, but before the leaves are fully expanded. If you use liquid lime sulfur when the leaves are fully expanded, they will be damaged.

Until dry weather comes in June, apply copper-containing sprays like Dragon Copper
Fungicide, Bonide Liquid Copper or Kop-R-Spray.

If we have a dry spring next year, you may get the disease under control by summer and have a nice crop of berries.

see
http://web.aces.uiuc.edu/vista/pdf_pubs/700.pdf