How to Tell If a Tree Is Diseased or Dying
Quick answer: A sick or dying tree usually shows several signs at once: thin, small or scorched leaves, dead branches at the top of the crown, cracked or peeling bark, fungi on the trunk or at the base, and sometimes a new lean. A tree that's declining but structurally sound can often be treated. A tree with major decay may need to come down.
Check the leaves
- Smaller, fewer or discolored leaves compared with previous years
- Leaves browning or dropping early in summer
- Spots, blotches or curling that spread year after year
Check the branches
- Dieback: dead twigs and branches at the top and outer edges of the crown
- The scratch test: gently scrape a small twig with a fingernail. Green underneath means it's alive; brown and dry means that part is dead.
- Brittle branches that snap instead of bending
Check the trunk and bark
- Cracks, splits or cankers (sunken, dead patches of bark)
- Oozing sap or wet, dark stains
- Holes, sawdust-like frass, or D-shaped exit holes (a sign of some borers)
- Bark falling away to show bare wood
Check the base and roots
- Mushrooms or shelf-like conks at the base, often a sign of root or trunk decay
- Soil cracking or heaving on one side
- Recent digging, trenching or heavy traffic over the roots
Dying vs dead vs hazardous
A declining tree may recover if the cause, such as drought, pests or root damage, is fixed. A dead tree gets more brittle every season and should come down before it fails. A hazardous tree is one likely to fail onto something that matters. Get it assessed quickly.
What to do next
- If it's still structurally sound, look into tree health care →
- If it's dead or has major decay, see tree removal →
- If it's a street tree, the City of Boise removes dead, diseased or hazardous right-of-way trees at no cost to the adjacent homeowner. Permit rules →
Sources: City of Boise: Tree Care · City of Boise: Tree Removal · University of Idaho Extension BUL 1077