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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Herbicide Drift Injury

This article was published originally on 6/13/2012

Several pictures and samples have been coming into the PIDC showing plants with curling of leaves and tips of growing points. Most of the samples have been tomato plants, but we’ve also seen symptoms on squash, bean, and trees. This kind of injury can be caused by exposure to growth regulator herbicides, such as 2,4-D and dicamba. Growth regulator herbicides are commonly used to control weeds in lawns and landscape areas.
 
During herbicide applications, very fine droplets or vapors can drift to areas where the application was not intended and as a result, vegetables, ornamentals, and urban trees can show herbicide injury symptoms.  It is difficult to determine how far the herbicide will drift as it will depend on several factors like type of herbicide, environmental conditions at the time of application, and sensitivity of surrounding plants.
 
Homeowners can decrease the risk of herbicide injury by avoiding applications during windy days and spraying at low pressures. If possible, avoid applications before highly sensitive plants like tomatoes, peppers, and potatoes are planted. Also, avoid using treated grass clippings as mulch near susceptible crops. It takes a long time for herbicides to break down and some of the chemicals can be picked up by the root system. 
 
Recovery of herbicide-injured plants will depend mostly on the amount of herbicide, persistence of the product in the soil, and sensitivity of the plant. Severely damaged plants may not always recover or be able to produce fruit. However, survival and recovery of the plant can increase by enhancing plant vigor with proper watering practices, pest control, and adequate fertilization.
 

 
Herbicide drift injury on tomato
  Herbicide drift injury on tomato. Photo by: Jenny Pollard

 Herbicide drift injury on pepperHerbicide drift injury on pepper. Photo by: Jenny Pollard