Honeysuckle samples showing a fungal leaf blight disease have been arriving in the Plant Disease Clinic during the past few weeks. The disease, caused by the fungus Insolibasidium deformans, first appears in the spring. Initially, the undersides of infected leaves show a silvery- white discoloration, usually in spots bound by the leaf veins. As the disease progresses, brown areas develop, often involving large portions of the leaves. Infected leaves eventually become entirely brown and distorted and fall prematurely.
Because the fungus overwinters in dead leaves, removing and destroying infected foliage will help control the disease. High humidity, poor air circulation, and moisture on leaves favor disease development. Pruning to improve air movement and avoiding wetting the leaves if irrigating are also important disease control measures. Finally, a protective spray program will minimize disease damage. Protectant fungicides (such as Daconil 2787) can be applied the newly developing foliage in the spring. Read and follow label instructions.
This article originally appeared in the July 14, 1995 issue, p. 103.