We recently received a sample in the Plant Disease Clinic of a strawberry plant with spots on the leaves. Strawberries in this region are commonly affected by three fungal leaf diseases--leaf spot, leaf scorch, and leaf blight. These diseases typically do not cause serious damage, but when they are particularly severe, they may reduce yield and make the plants more susceptible to devastating root diseases.
Leaf spot is the most common disease on strawberry. Symptoms at first appear as small, round purple spots on the upper surface of leaves. As the spots enlarge, the centers turn pale tan to white, with a purple or rust-colored border.
Leaf scorch appears as small, irregular purple spots or blotches on the upper surface of leaves. The spots enlarge and coalesce, often covering a large portion of the leaf. As they grow, the centers of the spots turn brown.
Leaf blight begins as small, purple spots. These spots enlarge into large, triangular-shaped lesions bounded by leaf veins. The centers of the lesions turn pale brown, with dark brown margins.
Management of all three of these diseases is similar. Some varieties are resistant to leaf spot and leaf scorch. Resistant varieties include the junebearing varieties Allstar, Canoga, Cardinal, Delite, Earliglow, Honeoye, Jewell, Lester, Midway, and Redchief, and the ever bearing varieties, Tribute and Tristar. Maintaining adequate spacing between plants, and managing weeds, helps to increase aeration and reduce leaf wetness. Infected leaves should be removed after harvest to reduce inoculum levels. Fungicide sprays may also be used to prevent infection by leaf diseases.
This article originally appeared in the 4/6/2005 issue.