Plant Disorders on Raspberry Leaves

Anthracnose

• Anthracnose is a fungal disease that usually affects the canes on raspberry plants, but it also causes discoloration on the leaves and fruit. Look for small, brownish-purple lesions on the canes and gray spots on the leaves. Anthracnose is most common during damp spring weather. Control anthracnose by pruning out infected growth, keeping the area around the plant clear of debris and spraying with a fungicide approved for use on food crops.

Spur Blight

• Another fungal disease, spur blight is more common on red raspberries than on black varieties. It causes premature leaf drop. Brown, blue or purple spots form on the canes and leaf petioles, the small stem that attaches the leaf to the cane. Infected leaves typically show brown, wedge-shaped lesions. Control spur blight with regular fungicide applications.

Root Rot

• While Phytophthora root rot is a disease of raspberry stems and roots, it causes the leaf margins to yellow, wilt and scorch. This fungus lives in the soil for many years, so never plant raspberries where other plants have succumbed to the disease, as there is no chemical control for it. Overwatering increases the plant's susceptibility.

Other Fungal Diseases

• Tan, gray or white spots on the upper leaf surfaces indicate the presence of raspberry leaf spot disease. Sometimes the center of the spot drops out. Powdery mildew looks like a white or gray powdery coating on the leaves and is rarely serious. It's most common in the spring. Rust appears as orange-yellow spots on both sides of the leaves. Orange rust infects black raspberries but not red ones. Treat all these fungal diseases with fungicides.

Viral Diseases

• Three types of viral disease are common on raspberry leaves. Raspberry mosaic disease causes the green leaves to develop yellow splotches or mottling, blisters, brown tips and stunted growth. It's transmitted by aphids. Raspberry leaf curl virus causes the leaves to curl and distort, and the plant dies within a few years. Dig up infected plants and destroy them; don't add them to your compost pile. The tomato ringspot virus shows up as yellow rings and lines on the leaves, as well as chlorosis or yellowing near the leaf veins. Control viral disease outbreaks by using only resistant varieties, controlling aphid infestations and practicing good garden hygiene.