Herbicide Injury by Mary Small

We have been blessed by an abundance of rain this spring.  It’s been great, not only for our gardens, but also for those pesky weeds.  Just as there are a variety of weeds, there are a variety of ways to manage them.  One of the most common methods is spraying them with herbicides (weed killers).  When used according to label directions, herbicides are quite successful.  However, some users fail to read the directions and that’s when problems occur.
We’ve started to see herbicide injury to garden plants in the CSU/Jefferson County Extension plant clinic.  Growing tips are twisted and curled; leaves may appear twisted, cupped or narrower than normal.  Leaf stems (petioles) may be twisted or curled.  Garden plants such as tomatoes, beans and lilacs are very sensitive.  Unfortunately, herbicides don’t “know” the difference between a desirable and an undesirable plant.   And it doesn’t have to be you that applied the product; herbicides can move from their target area (ie, a lawn) under the right conditions.
What can you do to avoid problems with herbicide injury? 

Watch the air temperature.  High temperatures (85 degrees or higher) during or right after application can cause some products to vaporize and move elsewhere (called “drift”).
Watch the wind speed.  Don’t apply products when it is windy or breezy.  Early day applications are often best to avoid “drift” from wind movement.
Use lower pressures or sprayer nozzles with larger openings that will increase the droplet size and make it more difficult for the product to move elsewhere.
Hold the sprayer nozzle as close to the plant as the product suggests so it doesn’t have a chance to become airborne.
Distortions or weird growths you find are not always  the result of herbicide injury.  Weather, soil problems, root stress, diseases, insects, mites and mutations can also cause these problems.  Have the problem checked out by the CSU/Jefferson County plant clinic.  We can’t test for herbicides in plants, but we can look for other problems.  The clinic is located on the Jefferson County fairgrounds in the Extension office.  There is a $7 fee for Jefferson County residents and a $10 fee for non-county residents.