Remember Proper Sprayer Cleanout Can Prevent Crop Injury

In 2017, we received a number of phone calls concerning crop damage in peas treated with herbicides containing the active ingredient clethodim. This year, I recently drove past a chickpea field near Pullman with a large portion of the field exhibiting severe crop damage (see photo). It made me think about 2017 and the need to remind people how important proper sprayer cleanout is, especially when switching from spraying one crop to another. Here is the TT from 2017, which is every bit as relevant in 2019 as it was in 2017.

Clethodim is an ACCase inhibitor (Group 1) used to control grass weeds in broadleaf crops. There is no clethodim activity on broadleaf crops like peas or chickpeas. So why do we sometimes see significant crop injury?

Clethodim products containing 26.4% or 2 pounds of clethodim per gallon (for example, Arrow 2 EC, Clethodim 2 EC, and Select 2 EC) contain as much as 70% petroleum distillates. This high level of petroleum distillates, combined with the required crop oil concentrate and liquid fertilizer additives, can act as a sprayer cleaner, dislodging old herbicide residues that are embedded in tank walls or hoses, resulting in unwanted herbicide residue in the sprayer liquid. It is these residues, and not the clethodim, that are causing crop injury.

The worst damage is typically from the first sprayer load. Plants treated with subsequent sprayer loads show little or no injury from the same herbicide treatment. This type of damage, which is not unique to clethodim products, can be avoided by properly cleaning sprayers between applications, particularly when changing what crop is being treated. While proper sprayer cleanouts are time-consuming, it can save a lot of money and misery. Removing Herbicide Residues from Agricultural Application Equipment is an excellent publication by Purdue Extension that can help you do a good job of sprayer cleanout and possibly save you headaches and dollars down the road.

Chickpea Damage Sprayer Cleanout.
Chickpea damage on the outside edge of a field near Pullman that was likely caused by insufficient cleaning of the sprayer. It appears that the first sprayer load caused significant injury to the chickpea, whereas subsequent sprayer loads did not cause crop injury.

For questions or comments, contact Drew Lyon by phone 509-335-2961 or via email drew.lyon@wsu.edu.
Washington State University