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Maple Diseases: Anthracnose, Root Rots, and Verticillium Wilt

Disease Reference Table

Disease	Symptoms	Pathogen/Cause	Management
Anthracnose	Norway maple: narrow purple/brown streaks along leaf veins. Sugar maple: large irregular brown/red-brown areas along/between veins (like drought/heat stress). Small brown fruiting structures near affected veins. Wet spring: some defoliation.	Discula (Gloeosporium)	Prune dead twigs/branches. Rake/destroy fallen leaves. Usually little damage; no treatment needed. Nursery: fungicide at bud break and 7–10 day intervals until weather dries and daily avg >65°F.
Bacterial Leaf Scorch (Red Maple)	Leaf margins on localized branches brown mid-late July. Light-brown area separated from green by dark reddish-brown band and narrow distinct yellow halo. Leaves may fall in August.	Xylella fastidiosa	Leafhoppers/spittlebugs carry bacteria. Promote plant vigor by protecting from stresses.
Bleeding Canker	Reddish-brown cankers in inner bark of main trunk/branches. Bark over canker sunken; reddish-brown sap oozes. Leaves wilt; branches die.	Phytophthora cactorum	Remove infected tree; do not replace with woody ornamental until soil fumigated and aerated.
Decline	Growth slows; branch dieback progresses until much of tree dead. Combinations of: poor soil aeration/drainage, deicing salt, high temps, drought, excavation damage, compaction, paving near trees, Verticillium wilt, Armillaria root rot.	Multiple	Protect from stresses, especially insect defoliation.
Fomes Root Rot	Hard, gray-topped, hoof-shaped fruiting structure (6–8" across), enlarges perennially. Underside white with tiny pores. Heart rot and dying limbs may be apparent.	Fomes fomentarius	Remove promptly if in hazardous location (property damage or injury risk).
Ganoderma Root Rot	Annual shelf-like fruiting structures, single/overlapping clusters, brown to reddish-brown with cream/white margin, up to 14" across; upper surface varnished. Branches and eventually entire tree die as root rot progresses.	Ganoderma lucidum	Remove promptly if in hazardous location.
Laetiporus Root Rot	Massive clusters of bright sulfur-yellow to salmon/orange shelves turning white with age. Form summer/autumn, fall off winter; new ones next season. Underside has pores. Bark at fruiting site depressed/cracked.	Laetiporus sulfureus (formerly Polyporus sulfureus)	Fruiting forms long after major damage. Trees prone to wind breakage before fruiting. Remove at first sign.
Leaf Spot	Spots up to ¼" diameter with pronounced purple border, round/irregular. Tiny black fruiting structures on upper spot surface.	Phyllosticta minima	See anthracnose control above.
Powdery Mildew	White fungal growth on upper leaf surfaces in late summer/autumn.	Phyllactinia	No control necessary—disease starts too late for significant damage.
Tar Spot	Oval to irregular shiny black spots up to ½" diameter on silver/red maple leaves.	Rhytisma acerinum or R. punctatum	No control measures necessary.
Verticillium Wilt	Early: heavy seed production, smaller-than-normal leaves, leaf margin browning. Often foliage on only one side wilts. Wood under bark of wilting branches discolored with green/black streaks. Smallest branches may not show discoloration.	Verticillium	Do not replant susceptible species where Verticillium killed a tree. Mild symptoms: prune affected limbs, water to maintain vigor. Some trees recover. Do not fertilize heavily.

Declining maple in mid-summer; Tar spot; Tar spot; Verticillium wilt xylem discoloration; Verticillium wilt.

Plant Disease: Sugar Maple White Spots: Harmless Lichens, Real Issue Likely Planting or Herbicide; Mysterious White Foamy Growth on Maple Trunk: Not Slime Flux; Japanese Maple Sunburn Recovery: Stress Management; Lichens on Trees: Harmless Indicators of Stress, Not Disease; Loquat Sudden Decline: Expert Recommends Local Diagnosis; Troubleshooting a Struggling Sunset Maple: Water, Nutrients, and Herbicide Risks; Maple Spindle Galls: Cosmetic Only, No Treatment Needed; That "Vine" on Your Maple Is Not a Root—Here's How to Remove It Safely; Maple Sunscald: Wrap, Fertilize, Protect from Borers; Maple Borer Infestation in Old Wound: Treatment and Risk

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