Honeysuckle leaf blight is caused by the fungus Insolibasidium deformans. The disease appears in the spring on newly emerging leaves. The first symptom is a yellowing of leaf tissue. This tissue becomes tan brown and finally necrotic and dry with brown areas involving an entire leaf or a large portion of it. The lower surface of infected leaves show a silvery-white coloration, caused by the presence of the fungus. The leaves are often rolled and twisted and drop prematurely. The fungus overwinters in dead leaves.
Plants grown at high densities develop dense foliage that reduces aeration and increases humidity, conditions that favor disease development. Where possible, reduce foliage density or grow seedlings as row crops to improve aeration and reduce humidity. Irrigation should be scheduled so that periods of high moisture and free water in and around foliage and stems are as short as possible. Any cultural practice that removes overwintering foliage will reduce inoculum sources (i.e. raking, burning). Severe outbreaks on valuable plantings can be prevented by an occasional application of a copper fungicide, Fore or clorothalonil (Daconil 2787).
This article originally appeared in the July 26, 1996 issue, p. 131.