Custom applicators get paid by the number of acres they cover. If you’re handling your own spraying, you likely have a list of 15 things to do once you finish spraying. There’s just one problem: Two very different chemicals must be applied on two crops in the same day, and that means cleaning out the sprayer before spraying the second chemical.

Time lost cleaning the sprayer could be devoted to covering more acres. The temptation to skimp on clean-out is strong.

It may be strong, but it’s not worth it, says Peter Illingworth. He is a mechanic and also maintains and operates the sprayer at Purdue University’s Throckmorton Agricultural Center.

Illingworth doesn’t feel that way just because he works at a farm where some of the fields are devoted to research plots. He feels that way because he has seen firsthand what happens when a sprayer isn’t cleaned out properly, and he knows it’s not pretty.

CLOSE-UP VIEW: Here’s what individual plants within the same field shown above looked like when examined closely. The damage is from herbicide that wasn’t completely cleaned out of the sprayer. (Fred Whitford, Purdue Pesticide Programs, PPP-108)

“With glyphosate and Liberty around, and now with dicamba herbicides, there is too much risk that you could have enough residual in the tank to damage a sensitive crop if you don’t clean it out properly,” he says. "And if there is enough residue left in the first batch, it won’t be long before you know it. Then all you can do is feel bad about it, because there is no way to reverse it.”

Get it right
The way to avoid that feeling is to follow the proper clean-out procedures in the first place, Illingworth says. He actually goes to extremes to make sure he gets as much residue out as possible. If protocol says add 150 gallons of rinse water, he may add 200 to 300 gallons.

The first important step after the tank is empty is to add water and spray it out in the field, he says. The Miller sprayer he operates is equipped with a reservoir that holds enough water for the first tank rinse. He moves it into the empty spray tank and then drives back over the field, spraying it out.

The second step is to add more water and rinse again, Illingworth says. He also sprays that rinse out in the field.

Finally, he adds water for a third rinse. Anything short of triple-rinsing is asking for problems, he says.

BE THOROUGH: Pete Illingworth takes as much time as necessary to triple-rinse this sprayer when switching from one chemical to another.