Herbicide injury to trees: what extension services describe

This page describes what the named extension services and the Missouri Botanical Garden say. It does not diagnose a tree, say whether any tree is safe or unsafe, name a product or a rate, or tell anyone to treat, replace or remove a tree. It is not advice on who may apply a herbicide: the guide to pesticide licences covers that.

What the sources call it

Utah State University Extension (Ornamental Pest Guide) says herbicides are designed to kill plants, and that misuse, volatilization, drift or root uptake can cause wide-ranging deformities, leaf and branch dieback and plant death. The Missouri Botanical Garden says herbicide damage can be hard to diagnose: a trained person can usually tell when a herbicide is a possible cause, but confirming it takes a laboratory test of plant tissue or soil while the chemical is still present, with a separate test for each suspected herbicide and no test available for some. More often, Missouri says, a circumstantial case is built from the damaged plants, the surrounding plants, the pattern of damage, the chance of damage given where the herbicide was applied, and the history of symptoms.

What it looks like

Utah State lists leaf deformation, twisting, cupping, yellowing, wilting, browning, scorching, brown spotting or speckling, narrowing, strapping and dieback. Missouri gives a similar list: curled or cupped leaves, stunted growth, discolored leaves or leaves with dead spots, and notes the same herbicide can cause different symptoms in different species. South Dakota State University Extension (Tree Pest Alert, South Dakota Department of Agriculture and Natural Resources forest health specialist John Ball) describes curled and cupped leaves on ash trees standing in dandelion-filled lawns as common symptoms of injury from lawn sprays containing growth-regulator herbicides. A later alert (September 30, 2026) describes a different picture from a burn-down herbicide with a high concentration of 2,4-D near a windbreak: foliage burned off with no twisting or curling at all. The same alert reports that another site's trees showed little of the usual curling at the tips, the most common sign of 2,4-D exposure.

How the sources say trees are exposed

Utah State names spray drift, volatilization (the herbicide turning to a gas), misuse and root uptake. South Dakota (May 27, 2026) says trees that are leafing out just before or during a lawn herbicide application are the most sensitive to injury, names ash, hackberry and lilac as the species most affected in its region and says maples and lindens, which leaf out earlier and have hardened leaves, are less affected. In a July 8, 2026 case South Dakota traced dieback and sprouting in a row of ash to a three-way herbicide with 2,4-D, MCPP and dicamba used along a fence line within a tree's height of the trees. It says roots can reach out as far as the tree is tall, and that the drip line is not the full extent of the root system. It quotes the product label as warning against use on or near desirable plants because injury may result. Missouri adds that dicamba applied to lawn that washes down to roots can leave trees and shrubs showing damage for several years as they slowly recover, and that weed-and-feed lawn products can be a source. A further South Dakota report describes a rangeland herbicide containing aminopyralid associated with dead hackberry and honeylocust, and says the label lists control of many tree species.

South Dakota (September 30, 2026) also says that farm herbicides carry higher concentrations of active ingredient than lawn products and that applying them off label to lawns can kill or injure woody plants in a neighborhood.

Look-alikes the sources name

Missouri says herbicides leave no calling card like mites, insects and diseases, so those should be ruled out first, and lists virus diseases, adverse weather, salt damage, drought, soil compaction, misapplied fertilizer, root stress and nutrient deficiencies as disorders that can resemble herbicide damage. It suggests asking whether the pattern fits drifting spray, whether more than one kind of plant is affected and whether symptoms appeared within one or two days of the suspected application. South Dakota (September 30, 2026) gives a boxelder case where herbicide was suspected after a neighbor's spraying: the trees lacked the common 2,4-D signs, and the white patches on the leaves were from a mite, which it says does not stop the leaves photosynthesizing. For a yellowing that can be confused with herbicide see iron chlorosis, where Colorado State University Extension notes soil-sterilant weed killers can leave tissue along the veins green.

Recovery, as the sources describe it

Missouri says recovery depends on the amount of damage and which herbicide was involved. It says trees and shrubs with minor damage from a broadleaf herbicide such as 2,4-D are likely to recover or show only minor damage, plants showing signs of growing out of the problem will likely recover, plants that lose vigor may not, and plants damaged by soil sterilants are the least likely to recover. South Dakota describes waiting to see whether buds are healthy and inner bark of twigs is green before judging a windbreak damaged by 2,4-D.

The other pages in this group are listed on the weather, soil and chemical damage page.