Pesticide destroys vegetable garden

Q. My husband used Ortho Weed B Gon Crabgrass control on the tops of some of the weeds in the garden. Based on this, can we plant vegetables in this garden area this year?

Name omitted for obvious reasons!

A. The first thing I did was find the label for this product to review the active ingredients. This information is listed on the front of the product in the bottom left corner. Unfortunately, this product has the following active ingredients: 0.10% Quinclorac, 0.22% MCPP-p, 0.12% 2,4-D, 0.05% Dicamba. In general, these products control broadleaf weeds. Nearly every vegetable plant, excluding sweet corn would qualify as a broadleaf weed.

The research shows the half-life of 2,4-D in the soil is about seven days. So, half of the product will be broken down every seven days. But – the Dicamba has a half-life of 7-42 days. This would be most of the growing season. Quinclorac has a half-life of 122-162 days (based on a Cornell study). Based on the research, you’ll need to leave the site barren and wait until next year to attempt to plant a vegetable garden. Any vegetables planted into this area will stunt and twist.

I get lots of questions like this, but the questions usually come in July and August when a neighbor has sprayed a similar product on a lawn next to the other neighbor’s vegetable garden. In the heat of the summer, the result is heavily twisted (and somewhat brittle) tomato plants.

The lesson here is to read the label before using any pesticide. Generally, the word pesticide is used to define an herbicide, insecticide or fungicide. The label in this case states, “For use on lawns.” Thus, it is not approved for use on vegetable garden areas. As for the summertime applications, the label states, “apply when daytime temperatures are between 45 and 90‚ó¶F.” This is because the product is volatile in hot, dry weather, meaning it can easily drift to non-target plants. Thus, avoid using these products in the summer.

Better options for controlling weeds before planting the vegetable garden include using a cover crop, covering the garden with a dark tarp or plastic or using a mulch like newspapers at planting time.

Here are some resources to determine what is wrong and other details for future planting in the area:

Herbicide persistence and half-life: http://go.osu.edu/herbicidesincompost

Effects on yield and quality: http://go.osu.edu/yieldandquality

What does injury look like? http://go.osu.edu/determininginjury

Eric Barrett is OSU Extension educator for agriculture and natural resources in Mahoning County. Call the office hot line at 330-533-5538 to submit your questions. Clinic hours are Mondays and Thursday from 9am-12pm, through October.