How do I treat a sick tree?

Work out what is wrong before you treat anything. A tree that looks sick may be short of water, sitting in soggy ground, buried in mulch or recovering from root damage rather than infected, and treating the wrong problem wastes money. Virginia Cooperative Extension puts it this way: the health of a plant may be affected by soil nutrition and texture, weather conditions, quantity of light, other environmental and cultural conditions, and animals, including humans.^[1]

Start with the tree's story

Identify the species first, because many problems affect only certain species. Then describe the symptoms and where you see them. The Virginia Department of Forestry suggests noting whether there are mushrooms at the base of the tree, exit holes from insects, or spots on the leaves, and taking photos that show the whole plant plus close-ups of the injury.^[2] Write down the date, the location and how many plants are affected.

Where the damage shows up matters. When the tops of plants wilt or die, one can generally infer that there is a problem with the root system.^[1] A problem that spreads gradually can point to a living cause such as an insect or a disease, while one that appears suddenly and stays in one spot points toward a nonliving cause.^[1] Damage across several different kinds of plants in one spot also suggests nonliving factors.^[1]

Check water, soil and mulch

These are the usual culprits, and you can fix them yourself. Drought and waterlogging produce many of the same symptoms on the aboveground parts of the plant, mainly chlorosis (yellowing leaves), abscission (shedding older leaves), and wilt.^[1] So do not guess. The USDA Forest Service's Tree Owner's Manual says the best way to know how often and how much to water is to check the soil moisture at 6 inches below the surface, and to water when dry.^[3] It also warns that watering too much is as dangerous as watering too little, because soil saturated with water for more than 24 hours can prevent roots from getting oxygen.^[3]

Mulch is the other common cause. Do not put mulch in contact with the trunk, and then pile mulch only 2 to 3 inches over the roots.^[4] Pull away any mound against the trunk, and do not put any type of fabric or plastic material under your mulch.^[4] Also look for stacked items, parked equipment or recent digging near the roots, since stacking items atop the roots causes soil compaction.^[4]

What not to do

• Do not fertilize on a hunch. The Tree Owner's Manual says to apply nitrogen fertilizer ONLY if diagnosis by an arborist indicates that it is necessary, and other fertilizers ONLY if a soil test shows that nutrients are lacking.^[3]
• Do not paint or seal wounds. Virginia Cooperative Extension's advice is to not use anything to cover pruning cuts or wounds, because trees seal their own wounds.^[4]
• Do not top the tree or cut flush to the trunk. The same publication says to cut on the outside of the branch bark collar.^[4]
• Do not spray before you know the pest. If it appears insects or pathogens are causing the problem, be sure to positively identify the pest so you can choose the most effective control measure.^[1]

Get a real diagnosis

If watering and mulch do not explain it, get the cause confirmed. The Virginia Department of Forestry lists three routes: consult its Tree and Forest Health Guide, contact your local DOF forester, or submit a sample to the Virginia Tech Plant Disease Clinic and Insect ID Lab.^[2] The Tree Owner's Manual adds that for yellow or brown leaves, sparse leaves, leaf spots, small leaves or wilted leaves, the answer is to call for advice from an arborist or a university plant diagnostic service.^[3] For a boxwood or other shrub, the same approach applies. See why boxwoods turn brown for one common case.

Pruning and pesticides have limits

Removing a dead branch you can reach from the ground is ordinary care. Anything more is not. The manual's rule is blunt: if you cannot prune your tree with both feet on the ground, hire an arborist, and if power equipment is required, hire an arborist.^[3]

Pesticides carry legal limits as well. Virginia says no person may apply or recommend for use any pesticide commercially without a pesticide business license and the employment of a certified commercial applicator.^[5] A homeowner cannot buy their way around a restricted-use product either: no one may use a pesticide classified for restricted use unless they have complied with the Board's certification requirements or are under the direct supervision of a certified applicator on-site.^[6] Read and follow the label on any consumer product you do use.

Stop and call a pro if

• The work is above your head. Anything that needs a ladder, climbing or a chainsaw is arborist work.^[3]
• A power line is near the branches. Never prune trees or branches that are within 10 feet of utility lines; contact your local utility company.^[3] Virginia law separately bars anyone working in a trade or business from placing a person, tool or ladder within 10 feet of an overhead high voltage line.^[7]
• An elm has bright yellow leaves on one or two branches. The manual lists this as Dutch elm disease and says to immediately call the university or an arborist.^[3]
• The trunk is cracked, has cavities or fungi, or the tree has started to lean. The manual lists cracks, fungi and cavities, a flat-sided trunk at the ground level and a recent lean among the dangers to check, and says that if anything is found, or if in doubt, contact an arborist.^[3]
• The treatment you are considering is a spray of a restricted-use product. That is licensed work.^[6]

Getting help in Virginia

If you suspect the tree is past saving, read how to tell if a tree is dead or dangerous. To decide whether to hire someone, see when to call a certified arborist and what an arborist costs in Virginia. Browse lawn and landscaping answers or tree and shrub health services.

When you want a professional look, describe the problem once and local businesses quote it.