Tree problems: how to know if something is wrong with your tree? Insects, Mites & Diseases Tree & Shrub Care Submitted by Elisa Edelstein Reviewed by Expert Patrick Parker, Director of Plant Health Care Most tree conditions don't develop overnight. They often begin with subtle changes, such as discolored leaves, a crack in the bark, or a branch that looks thinner than it did last season. Recognizing these early warning signs gives you more time to act, and early intervention often leads to more effective treatment and better long-term outcomes. This guide explains some of the most common tree diseases and symptoms, from leaf discoloration to structural concerns, so you know what to watch for and when it's time to bring in a professional. How to tell if your tree has a condition Trees communicate stress in relatively few ways. Once you know what to look for, you can perform a quick visual inspection and get a general sense of your tree's health. Start with the canopy. Is it full and evenly leafed out, or are sections thin or sparse? Compare one side of the tree to the other, since uneven growth can be an early sign of stress. Next, examine the leaves. Healthy leaves should have the expected color, size, and shape for the species and season. Yellowing, spotting, curling, or premature leaf drop outside the normal fall season may indicate an underlying issue. Move down to the branches. If you can safely reach a small twig, gently bend it. Living twigs are typically flexible with green tissue beneath the bark, while dead twigs are dry and brittle. Finally, inspect the trunk and root flare. Look for cracks, oozing sap, mushrooms or fungal growth, missing bark, or soil that appears lifted or disturbed around the base of the tree. These can all point to concerns below the surface. A single symptom doesn't always mean there's a serious problem. However, when several symptoms appear together or continue to worsen, it's time to have the tree evaluated by an experienced ISA Certified Arborist to identify the underlying cause and recommend appropriate treatment. Leaf conditions: What discolored or dropping leaves are telling you Leaves are often the first part of a tree to show signs of stress, making them one of the best early indicators of declining health. Yellow, brown, or spotted leaves Yellowing leaves, also known as chlorosis, may indicate nutrient deficiencies, poor soil drainage, compacted soil, or root stress. Brown spots or irregular blotches are often associated with fungal or bacterial leaf diseases. The pattern of discoloration can provide helpful clues. Yellowing between the leaf veins across much of the canopy often indicates nutrient or soil issues, whereas scattered spots on individual branches are more commonly associated with localized disease. Early leaf drop and wilting Leaves that fall well before autumn or wilt despite adequate soil moisture may indicate root damage, drought stress, or vascular diseases that interfere with the tree's ability to move water. Because these symptoms often affect the tree's internal water transport system, they should be evaluated promptly. Curled or distorted leaves Leaves that curl, cup, or become misshapen are commonly caused by sap-feeding insects, herbicide injury, environmental stress, or certain diseases. Since several different conditions can produce similar symptoms, an in-person evaluation is often the best way to determine the cause. Bark and trunk conditions: Damage you shouldn't ignore The trunk provides structural support and protection from insects, decay, and disease. Problems affecting the trunk are often more significant than cosmetic leaf issues. Peeling, falling, or missing bark Some trees, including sycamores and birches, naturally shed bark as they grow. However, bark that peels away in large sections, falls off in chunks, or exposes bare wood may leave the tree vulnerable to decay, insects, sunscald, and disease. It often signals an underlying health issue or previous injury. Cracks, splits, and seams in the trunk Vertical cracks or splits that develop suddenly or continue to widen may result from frost damage, storm stress, internal decay, or structural weakness. Deep cracks that extend into the wood, rather than affecting only the outer bark, warrant prompt evaluation because they may reduce the tree's structural stability. Soft wood or fungal growth at the base Mushrooms, conks, and other fungal growth at the base of a tree often indicate internal decay. Likewise, bark that feels soft or spongy near the base can signal advanced wood decay. These symptoms suggest the tree's structural integrity may already be compromised. Branch and canopy issues: When limbs and leaves decline together When symptoms appear throughout the canopy rather than on a single branch, they often indicate a more widespread health issue. Dead or dying branches (dieback) Branch dieback occurs when the ends of branches gradually die back toward the trunk. It may result from root problems, drought stress, insect activity, disease, or natural aging. Dead branches also create safety hazards because they can fall without warning. Thin or sparse canopy A canopy that appears thinner than in previous years often signals long-term stress from drought, compacted soil, root damage, insects, or disease. Since canopy decline typically develops gradually, comparing current photos with older ones can help identify changes early. Sudden branch drop Some tree species occasionally shed large, seemingly healthy limbs without warning, particularly during periods of hot, calm weather. Regular inspections and structural pruning can help reduce risk, especially for mature trees located near homes, driveways, sidewalks, or outdoor living spaces. Structural conditions: Signs a tree may become hazardous Some tree problems affect more than health. Structural defects can increase the likelihood of branch or tree failure, particularly during storms. A leaning tree: When should you be concerned? Not every leaning tree is dangerous. Many trees naturally develop a slight lean as they grow toward available sunlight. However, a lean that develops suddenly or is accompanied by exposed roots, cracking soil, or soil heaving around the base should be evaluated as soon as possible. In general, sudden changes deserve more attention than long-standing ones. Co-dominant stems and weak branch unions When two stems of similar size grow from the same point on the trunk, they may develop included bark instead of a strong branch connection. These co-dominant stems are more likely to split apart during high winds, heavy snow, or ice storms and are a common contributor to storm damage. Exposed or damaged roots Construction, excavation, grading, soil compaction, or root cutting can reduce a tree's ability to absorb water and nutrients and affect its stability. Because root damage often goes unnoticed until symptoms appear elsewhere in the tree, changes in the surrounding landscape or new construction should always prompt a closer inspection. When to get a professional opinion Many tree troubles can be spotted during a visual inspection, but determining whether they're cosmetic, temporary, or potentially hazardous requires experience. An ISA Certified Arborist can evaluate your tree's canopy, trunk, branch structure, root flare, and surrounding site conditions to identify the underlying cause and recommend appropriate treatment. They can also recommend tree and shrub care best practices. Depending on the issue, recommendations may include soil care, fertilization, pruning, cabling or bracing, insect or disease management, or, when necessary, tree removal. You can also learn more about your specific type of tree, or what may be affecting it, in our tree care resource center. Tree problems rarely improve by themselves. Nutrient deficiencies can weaken a tree's natural defenses against insects and diseases, insect damage can create entry points for decay organisms, and structural defects often become more severe over time. It’s important to address these issues right away for the best results for the long-term health of your trees. If you've noticed yellowing leaves, cracked bark, dead branches, mushrooms growing near the trunk, or a tree that's leaning more than it once did, it's worth having the tree evaluated before the problem progresses. Contact us today to schedule a consultation with an expert arborist.