Red Leaf Spot on Cranberry

CRANBERRIES

Red Leaf Spot
(Exobasidium rostrupii Nannfeldt)

Symptoms:
Red leaf spot is characterized by the presence of circular, bright red spots on the upper sides of leaves and occasionally on young green berries. The undersides of the leaf spots are paler and eventually become covered with a dense, white, powdery deposit. When several spots develop on a single leaf, they often grow together. Infected leaves are usually shed prematurely. Leaf infections may spread through the petiole (leaf stem) to the young growing vine, causing reddening and death of the stem. The part of the vine above the infected area may continue its normal growth or wither and die, depending on the amount of distortion of the stem tissue. Use of a lot of nitrogen will favor the onset of this disease. [Ben Lear variety is especially prone to this disease. Stevens variety is more immune to it than any other variety in Maine.]

Control:
The early stage of this disease is no cause for panic, and generally sprays for fruit rot will also control this disease. Kocide or Echo will offer protection against further infection. Injured plants will not be cured, but the infection will be prevented from spreading.

If you have comments or questions about this page,
contact Charles Armstrong at: charlesa@umext.maine.edu

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These pages are currently being maintained by the Pest Management Office, University of Maine Cooperative Extension. Page Last Modified: 04/11/08