Leaves on Akami Maple

Asked May 27, 2014, 2:36 PM EDT

The leaves on my Japanese maple show brown spots and unhealthy dark colorations. Can you give me any idea of what this might be?

Hood River County Oregon

1 Response

There is more than one thing this could be and a digital picture would help.
Please read the description of this problem and see if it fits your tree.

PNW Plant Disease Management Handbook
Printed page URL: pnwhandbooks.org/plantdisease/node/3528

Maple (Acer spp.)-Phyllosticta Leaf Spot

Cause Phyllosticta minutissima, a fungus, has been reported from Oregon and Washington. Not considered an economic landscape problem. Spores are thought to be rain splashed. Symptoms On different maple species, spots vary considerably in shape, size, and color. Usually they are small, irregularly circular, and reddish brown with narrow to broad purplish borders. Small, black, fruiting bodies (pycnidia) may be seen in the necrotic areas and may be arranged in a circular pattern. On Japanese maple, which the disease may severely damage, spots are a straw to tan color with a definite margin. The spot's center may be transparent. On sugar and Rocky Mountain maples, spots commonly have a narrow, purplish border. Diseased tissue often falls out, leaving holes in the leaf. Cultural control
  • Rake and destroy fallen leaves.
  • Avoid overhead irrigation for short trees in the landscape.
Chemical control Spray when leaf buds are opening and twice more at 10-day intervals if season is wet. Many of the same fungicides that control anthracnose will most likely control this leaf disease as well.
  • Bordeaux 8-8-100. O
  • 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.
  • Pentathlon DF at 1.5 lb/A 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 can be used for tree injections. The number of capsules used is based on tree size.
Reference Mayer, J.S. 1987. Triforine controls Phyllosticta leaf spot on silver maple. F&N Tests 42:173-174.
Pscheidt, J.W., and Ocamb, C.M. (Senior Eds.). 2014. Pacific Northwest Plant Disease Management Handbook.
© Oregon State University.

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