News release: Herbicide Injury in Horticultural Crops, Part II

Tim Baker, MU Extension Horticulture Specialist
102 N. Main, Suite 1, Gallatin, MO 64640

Release Date: April 26, 2018
Headline: Herbicide Injury in Horticultural Crops, Part II

In my last column, I mentioned the types of herbicide damage that I have seen on horticultural crops through the years. This week, I would like to mention measures and resources that both growers and applicators might want to consider to avoid these situations.

The first resource that I will mention is good for both growers and applicators. It is a web-based map of sensitive crops called DriftWatch. You can find this site at There are also two related web sites, FieldWatch and BeeCheck.  The latter site is for beekeepers who are concerned about insecticide drift. 

The grower or beekeeper uses these sites by identifying the location of their farm on an aerial map on the web. Applicators who might be concerned about damaging nearby crops can consult the map to see if there are any sensitive crops or bees nearby.

Another great resource for applicators is a web site that predicts the likelihood of thermal inversions. This is especially important for herbicides that are subject to volatility problems.  It can be found at:

For growers, a great way to help avoid problems is simply to talk to your neighbors who may need to spray chemicals that could drift and cause damage to your crops. Some applicators are simply not aware of how sensitive and valuable many horticultural crops are.

So what do you do if your crop is damaged by a non-labeled, off-target herbicide?  First, be sure that it really is chemical damage. And, if there is damage, whether the herbicide is capable of the extent of damage which occurred. Sometimes, while there may or may not be herbicide damage symptoms, the actual damage of the crop was caused by something else, such as disease.

You might also look around.  Have other species of plants been damaged? Look at nearby weeds.  Are they showing similar symptoms?

If the damage is truly caused by the herbicide, you might want to consider calling the Missouri Department of Agriculture, Bureau of Pesticide Control. They have trained inspectors all around the state who can come to your farm to see what might have occurred. They will take samples to send to a lab. You do have to be willing to sign a letter of complaint.

There is one precaution about samples. I recently gave a presentation at the Indiana Horticulture Congress, a meeting similar to our Great Plains Growers Conference. One of the sessions that I attended was a workshop on herbicide injury. One speaker mentioned that while a positive lab result will prove that a herbicide was present on the damaged sample, a negative result will not be conclusive. 

In other words, just because the lab could not find a herbicide residue on your crop doesn’t mean it wasn’t there at some point. Some herbicides break down very quickly, sometimes in a matter of hours. Synthetic auxins are particularly bad for this, and by the time you see the damage, the herbicide has broken down and is gone.