Question 1

My maple leaves have black tar-like spots. What is it and is it harmful?

Accepted Answer

Those raised, shiny black spots are tar spot Rhytisma species, a fungal disease that's very common on maples — especially Norway, silver, and red maples. Despite its alarming appearance, tar spot is almost entirely cosmetic. What you're seeing: - Small yellow spots appear in early summer, then develop into raised, tar-like black blotches up to 3/4 inch across by late summer - The spots are the fungal fruiting structures; they cannot be rubbed off - Heavy infections can cause some early leaf drop

Question 2

My dogwood has brown blotches on the leaves and is dying back. What's wrong?

Accepted Answer

Brown blotches with purple margins on a flowering dogwood, combined with branch dieback, point to dogwood anthracnose Discula destructiva — a serious fungal disease that has devastated native flowering dogwoods, particularly in cool, moist, shaded settings. Signs of dogwood anthracnose: - Tan leaf spots with purple rims, often starting on lower and interior leaves - Blighted leaves that cling to the tree instead of dropping - Dieback of twigs and branches, progressing from the bottom up - Canker

Question 3

My pine/arborvitae is turning brown on the inside. Is it dying?

Accepted Answer

Good news: browning on the inner needles of pines, arborvitae, and other conifers in late summer or fall is usually seasonal needle drop — a completely normal, natural process, not a disease. Why it happens: - Evergreens are not truly "ever green" — each needle lives only 2-5 years depending on species - Older, interior needles closest to the trunk are shed first, turning yellow then brown - This is most noticeable in fall and can appear suddenly, alarming homeowners - White pines are especially

Question 4

My oak tree has brown wilting leaves in July, is it oak wilt?

Accepted Answer

Brown, wilting leaves on an oak in mid-summer are a classic red flag for oak wilt Bretziella fagacearum, one of the most destructive tree diseases in the Midwest. However, several other conditions can mimic these symptoms, so proper diagnosis is critical. Key signs of oak wilt: - Leaves brown from the edges inward margins first, then the whole leaf - Wilting progresses rapidly from the top of the canopy downward - Red oaks can die within 4-6 weeks of first symptoms; white oaks decline more slowl

Question 5

What are the black spots on my spruce needles?

Accepted Answer

Black spots on spruce needles are most commonly caused by Rhizosphaera needle cast Rhizosphaera kalkhoffii, a fungal disease that is extremely prevalent on Colorado blue spruce and occasionally affects other spruce species. How to confirm Rhizosphaera: - Examine the undersides of affected needles with a hand lens 10x magnification - You'll see rows of tiny black fruiting bodies pycnidia emerging from the stomata — they look like fuzzy black dots arranged in neat lines - Infection typically start

Question 6

My tree's leaves are covered in a white powdery substance. What is it?

Accepted Answer

The white powdery coating on your tree's leaves is almost certainly powdery mildew, one of the most common and easily recognized fungal diseases of trees and shrubs. It's caused by various species in the order Erysiphales, and different host trees have their own specific powdery mildew strains. Commonly affected trees: - Dogwood, crabapple, oak, maple, and sycamore are highly susceptible - The fungus thrives in warm days 60-80°F with cool, humid nights - Unlike most fungal diseases, powdery mild

Question 7

There are orange jelly-like blobs growing on my cedar tree. What are they?

Accepted Answer

Those striking orange gelatinous masses are the telial horns of cedar-apple rust Gymnosporangium juniperi-virginianae, a fascinating fungal disease that requires two different host trees to complete its life cycle — junipers/cedars and apple/crabapple trees. How the disease cycle works: - Brown, golf ball-sized galls form on cedar/juniper branches these develop over 18 months - During warm spring rains, bright orange gelatinous tendrils telial horns emerge from the galls — this is what you're se

Question 8

Dark liquid is oozing from my tree's bark. Is my tree dying?

Accepted Answer

Dark liquid oozing from bark — called slime flux or bacterial wetwood — is a common condition caused by bacteria fermenting sap inside the tree. While it looks alarming, it's important to understand the difference between wetwood and more serious oozing. Bacterial wetwood / slime flux: - Foul-smelling, dark liquid seeps from wounds, cracks, or branch crotches - Often leaves a grey-white streak down the bark as it dries - Common in elms, maples, oaks, poplars, and willows - Caused by several anae

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