Cause Discula sp. and Aureobasidium apocryptum, fungi. They often are found on many different maple species throughout the Pacific Northwest and are favored by warm, wet springs. Not considered an economic problem in the landscape.
The Discula disease can be significant in the Southeastern United States with the sugar maple cultivars Fairview, Gold Spire, Flax Mill Majesty, Seneca Chief, Sugar Queen, and Sweet Shadow developing considerable defoliation. The sugar maple cultivars Autumn Blush, Autumn Faith, Fall Fiesta and Legacy were found to be the most resistant.
Symptoms Symptoms vary depending on the plant and fungus involved. Usually there are vein-associated lesions, discrete necrotic spots, and/or irregular necrotic blotches or blights. Acervuli usually are produced in the necrotic spots, which may or may not be conspicuous. Severely diseased trees can defoliate early. Twig cankers or lesions also can develop where fungi can overwinter.
- Rake up and destroy fallen leaves.
- Remove and destroy twig cankers during dormant pruning.
- Avoid dense plantings in nurseries and time irrigation to minimize the time leaves are wet.
Chemical control If needed, apply early in spring during budbreak and early shoot growth.
- Armada 50 WDG at 3 to 9 oz/100 gal water. Do not use a silicone-based surfactant. Not for nursery or greenhouse use. Group 3 + 11 fungicide. 12-hr reentry.
- Banner MAXX at 5 to 8 fl oz/100 gal water may be effective. Group 3 fungicide. 12-hr reentry.
- Bonide Fung-onil Multi-purpose Fungicide at 2.25 teaspoons/gal water. H
- Daconil Weather Stik at 1.4 pints/100 gal water. Group M5 fungicide. 12-hr reentry.
- Mancozeb-based products. Group M3 fungicides. 24-hr reentry.
- Fore 80 WP at 1.5 lb/100 gal water plus a spreader-sticker.
- Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker.
- Spectro 90 WDG at 1 to 2 lb/100 gal water. Group 1 + M5 fungicide. 12-hr reentry.
- Tebuject 16 is registered for tree injections. The number of capsules used is based on tree size. Group 3 fungicide.
- Thiophanate-methyl-based products. Group 1 fungicide. 12-hr reentry.
- Cleary's 3336 EG at 12 to 16 oz/100 gal water.
- OHP 6672 4.5 F at 10.75 to 20 fl oz/100 gal water.
- Tourney 50 WDG at 1 to 4 oz/100 gal water. Group 3 fungicide. 12-hr reentry.
Note Some registered products offer only suppression of this disease and thus are not recommended for use. These products include Phospho-Jet.
Reference Hagan, A.K., Bowen, K.L., Conner, K., Sibley, J. and Caylor, A. 2016. Reaction of selected cultivars of sugar maple to anthracnose in North Alabama. Plant Health Progress 17:273-278. DOI: 10.1094/PHP-RS-16-0047.