Cause Apiognomonia veneta (asexual: Discula platani), a fungus that overwinters on infected sycamore twigs and dead leaves. Anthracnose is a common disease of the western sycamore, Platanus racemosa; the American plane tree, P. occidentalis, and the London plane tree, P. acerifolia. On sycamore, the disease is most severe in spring if the average daily temperature at leafing-out and for the next 2 weeks is below 55°F. In spring, fungus in diseased tissue produces spores, which spread by rain or wind to cause new infections. Cultivars and seedlings vary widely in susceptibility. 'Bloodgood,' and 'Liberty' are reported to be resistant while 'Columbia' and 'Yarwood' are susceptible in western Oregon.
Symptoms Blight is noticeable early in spring as leaves expand. Young leaves turn brown and die as they emerge from buds, or infection may be later as brown blotches or irregular spots on either side of the main leaf vein. Blotches enlarge and coalesce, ultimately covering much of the leaf surface. If the disease is severe, infected leaves fall; in some cases, almost the entire tree is defoliated except for terminal leaves. Newer infections are more rapid in moist weather, so the disease is more severe in wet springs.
If the disease goes back into older twig growth, cankers may form at the twig base; growth originating from that point is girdled and dies. A bushy growth often is in diseased trees due to death of terminal buds and the resultant stimulation of dormant lateral buds, giving the tree a willowy, broom-like appearance.
- Prune out and destroy infected twigs and branches. This may be difficult if affected twigs and branches are small and numerous and the tree too large for detailed pruning.
- Rake and destroy fallen leaves and twigs.
- Maintain tree vigor with adequate water and fertilizer.
- Space trees out in nursery production for good air circulation.
- Avoid overhead irrigation that keeps plants wet for an extended period of time.
- Spray a fungicide when buds swell and bud caps begin to break. Spray again 10 days later.
- Armada 50 WDG at 3 to 9 oz/100 gal water. Do not use a silicone-based surfactant. Not for nursery or greenhouse use. A Group 3 + 11 fungicide. 12-hr reentry.
- Banner MAXX at 5 to 8 fl oz/100 gal water may be effective. 12-hr reentry.
- Bonide Fung-onil Multi-purpose Fungicide at 2.25 teaspoons/gal water. H
- Champ WG at 2 to 4 lb/100 gal water. 48-hr reentry.
- Copper-Count-N at 2 to 3 quarts/A. 12-hr reentry.
- Cuprofix Ultra 40 Disperss at 1.25 to 2 lb/A. 48-hr reentry.
- Daconil Weather Stik at 1.4 pints/100 gal water. 12-hr reentry.
- Kocide 3000 at 0.75 to 1.25 lb/A. 48-hr reentry.
- Nordox 75 WG at 1.5 to 2 lb/A. 12-hr reentry. O
- Nu-Cop 50DF at 2 to 3 lb/100 gal water. Nu-Cop 50 WP can be used for organic production. 24-hr reentry. O
- Ortho MAX Garden Disease Control at 2 teaspoons/gal water. H
- Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker. 24-hr reentry.
- Spectracide Immunox at 1 fl oz/gal water is registered for powdery mildew and be effective on this disease. H
- Spectro 90 WDG at 1 to 2 lb/100 gal water. Group 1 and M5 fungicide. 12-hr reentry.
- Thiophanate-methyl-based products. Tank-mix or alternate with another product. 12-hr reentry.
- AllBan Flo at 10.75 to 20 fl oz/100 gal water.
- Cleary's 3336 WP at 12 to 16 oz/100 gal water.
- Halt (by ferti-lome) at 2.5 teaspoons/gal water is registered for home use. H
- 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. 12-hr reentry.
- Zyban WSB at 24 oz/100 gal water. Not to be confused with the smoking cessation drug. 12-hr reentry.
- Tree injections.
- Arbotect 20-S at 4 fl oz for each 5 inches of trunk diameter, diluted with 80 to 160 fl oz water. Gave excellent control over multiple field-trial seasons.
- Fungisol for spring application only.
- PhosphoJet is registered; rates are based on tree size. 4-hr reentry.
- Phyton 27 is registered; rates are based on tree size. Ineffective to poor control. 24-hr reentry.
Reference Himelick, E.B. and D. Neely. 1988. Systemic chemical control of sycamore anthracnose. Journal of Arboriculture 14:137-141.