Don’t let herbicides, insecticides cross paths
Q: I sprayed my lawn for weeds, and now my vegetables don’t look so good. Could the weed killer somehow have gotten onto my vegetables even though I didn’t spray in the garden?
— Ayan from Youngstown
A: Yes, there are ways that lawn spray (herbicide) can get on your vegetables even though you didn’t spray them. You didn’t say, but I’ll assume you were spraying for broadleaf weeds, as this is a common practice for many home lawns across our area. Many products for these weeds contain the herbicides Dicamba and or 2,4-D.
We have had several questions in the clinic this year about herbicide damage to vegetables and ornamental plants. One symptom of herbicide damage is the twisting, curling and cupping of the leaves a few days after spraying in the area. Some diseases and nutrient deficiencies can also cause these symptoms, but if you know a herbicide has been sprayed recently, it is the most likely cause.
The two main ways herbicide can move from a sprayed area onto other plants are drift and volatilization.
Drift happens during spraying. Small droplets of the spray are picked up by the wind and blown onto unintended plants. Anytime the wind speed is above five miles per hour drift can happen.
Volatilization refers to the ability of an herbicide to vaporize, mix with air and then land on other plants. This happens after spraying. How much volatility happens depends on the type of herbicide and the temperature. Usually, 85 degrees is used as the threshold where herbicides are most likely to vaporize.
Both Dicamba and 2,4-D can drift or volatize. There is a common label warning not to spray these products once a certain air temperature is reached.
There are two other less common ways for herbicides to move to where you don’t want them — using the same sprayer for insecticides and herbicides, as well as by mulch or compost.
To avoid the first, do not use the same sprayer for insecticides and herbicides. Residual herbicides in a sprayer can still harm plants if the sprayer is not properly cleaned. If the material you use for mulch was previously treated with herbicide, those herbicides can still be present and can damage your plants.
The same applies to compost that may have material that was sprayed with herbicide. Since it’s hard to know if mulch or compost has contaminants, get it from reliable sources to be sure.
Your vegetables may recover; it depends on how much herbicide they absorbed. If you think a herbicide has accidentally gotten onto a plant, wash the plant off with water as soon as you can to minimize the damage. But, when it comes to edible plants, when in doubt — throw it out.
At our clinic in Canfield, we cannot test for herbicides. That kind of testing can get quite expensive. Thus, it is best to do what you can to reduce or eliminate herbicide use near sensitive and desirable plants. Alternatives to herbicides for lawns can be found at http://go.osu.edu/organiclawn.
For more information on herbicide injury, go to http://go.osu.edu/herbicideinjury. To learn about herbicide carryover in compost, go to: http://go.osu.edu/herbicidesincompost.