Unintended Consequences

Herbicide phytotoxicity – whew!  That’s a mouthful!  What is it? Phytotoxicity is injury to plants caused by chemicals like air pollutants, fertilizers, and pesticides.  Herbicides aka weed killers, are designed specifically to kill plants, posing a significant risk of damaging desirable plants that are exposed these weed killers. 

Landscapes can be injured as a result of herbicide application and movement (e.g., drift) from nearby properties, rights-of-way, or turf, and when tree roots grow in treated soil.

Herbicide damage is usually most severe on plants nearest to where it was applied. Unlike with most diseases and insects, when an herbicide is the cause, often more than one plant species is damaged. Each type of herbicide or chemical family produces characteristic damage symptoms, including:

  • malformed, distorted leaves and shoots
  • stunted shoots and roots
  • chlorotic, necrotic, or spotted leaves

In some cases, plants will be stunted, growth will be atypically slow. In the worst cases, desirable plants will die. If herbicide damage is suspected, closely examine adjacent plants for similar symptoms, as herbicide overspray or drift rarely affects just one plant. Light herbicide damage to trees and other healthy, well-established landscape plants may not cause plant death. If symptoms of herbicide damage are already seen, it is too late to remove an herbicide; however, root damage by an absorbed herbicide may be limited by thoroughly irrigating the area to reduce plant moisture stress, as well as to flush loosely soil-bound herbicides through the soil. Rinse exposed foliage of desirable plants with clean water immediately after application to aid in the removal of spray residue and limit the absorption of the herbicide. However, be aware that roots may still take up some herbicides.

Learn more about herbicide phytotoxicity.  If you have additional questions about this or other plant problems, contact the Marin Master Gardener’s Help Desk at helpdesk@marinmg.org

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