Herbicide injury

About

Weed killers can twist, cup and stunt garden plants that were never meant to be sprayed. Lawn herbicides like 2,4-D and dicamba drift or vaporize onto gardens, and a few long-lasting herbicides survive in manure and compost.

Also called herbicide injury, herbicide drift, herbicide damage

How to recognize it

Symptoms

Growth-regulator herbicides (2,4-D, dicamba, triclopyr) make new leaves narrow, cupped, twisted or strap-like with odd, parallel veins, and stems twist or split; tomato fruit may be misshapen. Glyphosate yellows or whitens new growth between the veins. Symptoms often take a few days to 2 weeks to show.

Often confused with

Nutrient shortages and other stresses can look similar, so a professional diagnosis may be needed, especially before a formal complaint.

Worse when

Spraying on windy days or very still days (under 3 mph), hot weather that makes some herbicides vaporize, and garden inputs from treated pastures or lawns.

How it spreads

Drift and vapor move through the air during and after spraying; persistent herbicides (aminopyralid, clopyralid, picloram, aminocyclopyrachlor) pass through livestock into manure and can stay active in compost and soil for a year or more.

When

Spring and early summer, when lawns and fields are sprayed; any time contaminated compost or manure is used.

What to do, gentlest first

This is not an infection, so sprays for diseases won't help. Fix the cause below.

1. Keep weed killers away from the garden Prevent

   Avoid broadleaf lawn sprays near the garden, never spray on windy, dead-calm or hot days, and do not mulch with clippings from treated lawns (UMN suggests waiting four to six mowings after treatment).

   Tomatoes, peppers, eggplant, beans and grapes are very sensitive; grapes have been damaged by as little as 1/800th of a labeled rate.

2. Test manure and compost before using it Prevent

   Ask suppliers whether manure, hay, straw or compost could contain persistent herbicides. To check, mix the material 1:1 with potting mix, plant three pea or bean seeds per pot, and watch 2 to 3 weeks for twisted, cupped growth.

3. Document it and report drift By hand

   Take dated photos, note the weather and any nearby spraying, and talk with the neighbor or applicator. To file an official complaint, contact your state department of agriculture (the state pesticide regulator), which investigates at no cost to you.

   An official complaint starts a process you cannot stop, and investigations can take a year or more.

4. Care for injured plants By hand

   Plants that were drifted on, not directly sprayed, often outgrow the damage after several weeks with regular watering, though harvest may be delayed.

   Do not overfeed. Plants grown in soil or compost with persistent herbicide residues are unlikely to produce a usable crop.

Plants it affects

Apple (backyard tree), Beet, Carrot, Eggplant, Grape, Green beans (snap beans), Lettuce, Peach, Peas, Pepper (sweet and chili), Potato, Raspberry, Spinach, Strawberry, Tomato