Spur Blight or Purple Blotch (Didymella Applanata)
Spur blight (Didymella applanata) is a dangerous fungal disease of blackberry
Spur blight (Didymella applanata) is a fungal disease of blackberry. The disease is caused by a fungus Mycosphaerella rubina.
The winter spores are developed during the fall and early spring in the little black pustules. These spores remain immature over winter, but mature early in the spring. They are discharged in the early part of May and, falling on the young shoots, start a new infection. The summer spores bring about infection later in the season.
The first appearance of the disease is a brown or purplish-brown discoloration on the young canes just below the leaf stems. This appears about the middle of July and is observed only on the lower part of the cane. During the remainder of the season the lesion spreads up and down the stem, so that the stem is· discolored for a distance of several inches above and below the node, or leaf junction. Usually the bark splits longitudinally and becomes dry and brown. As the lesions become older they turn to a tan-gray color. In September small black pustules appear on the surface of some of the lesions. These are not always found near the center of the diseased area but may be near the outer edge in isolated patches. As a result, emerging lateral shoots are weak, fruit production is reduced, and canes wilt. Leaves can become infected. Brown wedge-shaped lesions develop. Infected leaves fall while petioles remain intact.
Use DiseaseEx, Mancozeb, Immunox and fixed copper (Bordeaux mixture) and sulfur fungicides to prevent spur blight disease on blackberries. Also remove any canes with suspicion on spur blight.
Affected plants should be removed and destroyed.
The winter spores are developed during the fall and early spring in the little black pustules. These spores remain immature over winter, but mature early in the spring. They are discharged in the early part of May and, falling on the young shoots, start a new infection. The summer spores bring about infection later in the season.
The first appearance of the disease is a brown or purplish-brown discoloration on the young canes just below the leaf stems. This appears about the middle of July and is observed only on the lower part of the cane. During the remainder of the season the lesion spreads up and down the stem, so that the stem is· discolored for a distance of several inches above and below the node, or leaf junction. Usually the bark splits longitudinally and becomes dry and brown. As the lesions become older they turn to a tan-gray color. In September small black pustules appear on the surface of some of the lesions. These are not always found near the center of the diseased area but may be near the outer edge in isolated patches. As a result, emerging lateral shoots are weak, fruit production is reduced, and canes wilt. Leaves can become infected. Brown wedge-shaped lesions develop. Infected leaves fall while petioles remain intact.
Use DiseaseEx, Mancozeb, Immunox and fixed copper (Bordeaux mixture) and sulfur fungicides to prevent spur blight disease on blackberries. Also remove any canes with suspicion on spur blight.
Affected plants should be removed and destroyed.
