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Proper Sprayer Cleanout Can Prevent Crop Injury

Posted by Blythe Howell | June 20, 2017
The strip of winter peas in the middle of this picture were sprayed with Clethodim 2 EC, but the observed injury was from the previous products in the sprayer: Huskie + Osprey. A water rinse is never adequate when using a tank-cleaning herbicide like clethodim. This injury could have been avoided by carefully cleaning the sprayer before switching from spraying wheat to spraying peas.
The strip of winter peas in the middle of this picture were sprayed with Clethodim 2 EC, but the observed injury was from the previous products in the sprayer: Huskie + Osprey. A water rinse is never adequate when using a tank-cleaning herbicide like clethodim. This injury could have been avoided by carefully cleaning the sprayer before switching from spraying wheat to spraying peas.

We have received a number of phone calls recently concerning crop damage in peas treated with herbicides containing the active ingredient clethodim. 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. So why is there sometimes injury to peas?

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 injuring the peas.

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.


For questions, contact Drew Lyon (509-335-2961 or drew.lyon@wsu.edu) or Ian Burke (509-335-2858 or icburke@wsu.edu).

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