Two common disease problems on raspberries are cane blight and verticillium wilt. CANE BLIGHT causes canes to wilt and die while loaded with fruit. Late in the season, brownish-purple areas appear on cut or injured parts of the cane. These discolored areas spread down the cane and encircle it. Cane blight cannot be cured. Remove and burn all affected stalks.
The second disease is VERTICILLIUM WILT. This disease causes lower leaves to develop an off-green or yellowish-bronze tinge in June or early July. The leaves curl upward, then turn brown and fall off, beginning at the base of canes and progressing upward. Sometimes a sudden wilt occurs in hot, dry weather. Canes show blue or purple streaks. Red raspberry is more resistant, symptoms show up later in the season, and discolored leaves turn upward. It is difficult to see cane streaks in red raspberries because of the natural color in them. Infected plants eventually die. Remove and destroy infected and surrounding plants. For future plantings, avoid heavy, poorly drained soils, and buy disease-free stock. Avoid planting new plants in soils which were formerly planted to other plant hosts of verticillium wilt.
References: