Recognizing Herbicide Spray Injury

Every year there are many instances of spray damage to vegetable gardens, flowers, trees and shrubs from lawn weed killers. Can you recognize the symptoms?

The damage happens when lawns are sprayed for weeds, and the herbicide drifts or is oversprayed onto plants that are next to the lawn. The ingredients in the common lawn herbicides, 2,4-D and dicamba, can easily injure garden and landscape plants. In fact, all broadleaf, non-grass plants can be injured. These weed sprays are easily recognized by their distinctive aroma as lawns are being sprayed.

I was taught in weeds class that if you can smell the herbicide in the air, it means there are spray particles in the air, and vegetables plants, flowers and trees in the vicinity are “breathing” that same air that you can smell. They are absorbing molecules of  the herbicide.

Some plants are more sensitive to herbicide than others. Tomatoes, grapes, amur maple, and boxelder are very sensitive. The extent of injury on any plant depends upon how much herbicide drifted onto the non-target plants, or if the plants are directly sprayed.

Spray damage on tomato foliage
Spray damage on linden tree leaves.

Spray injury symptoms can be slightly different on each plant type. But generally symptoms include curled, gnarled, stringy growth. Leaves become weirdly elongated, cupped and often hard-waxy.

Damage on grape vines.

What can be done if herbicide drift damages plants? Not much, and that’s why it’s so important to avoid the problem. If herbicides are accidentally sprayed onto “good” plants, you can immediately wash the plants off. But in most cases spray damage or drift goes undetected until symptoms occur, and then it’s too late to do anything.

Will plants recover? It all depends on the amount of herbicide the plants absorb. Some plants recover, others don’t. Spray damage on trees and shrubs can be cumulative, causing gradual decline if exposed yearly over a number of years. Many farm shelterbelts have suffered and exhibited much dead wood due to continued years of exposure to drift from field weed sprays.

Can vegetables be eaten from gardens that have showed signs of herbicide injury? There is no practical test to determine how much herbicide has been absorbed into the edible portion. So the standard recommendation is to put safety first and don’t eat vegetables from garden that show symptoms.

Many homeowners are re-thinking the ideal lawn. Perhaps spraying a lawn continuously with chemicals that have the potential to harm neighboring plants and vegetables isn’t such a wise idea. There are other methods of encouraging grass while discouraging weeds, but that’s topic for another day.