A mom told her daughter to spray weeds around the house and yard. The daughter wanted to please her mom, and she knew her mom wore herself out weeding around trees and other objects in the yard. So the daughter gathered up a backpack sprayer and several bottles of herbicide and started spraying. She sprayed until she ran out of herbicide.

That was last August. This is spring. There is a distinct foot-wide circle of bare soil around every tree and a foot-wide bare strip along the house. Everywhere the daughter sprayed, there is nothing growing.

Her mom is mad! All the daughter can say is she thought her mom was tired of fighting edging and trimming, so she poured on the herbicide.

Indeed, that’s a prime example of what can happen if you follow instincts instead of the label. If the daughter had applied anywhere near the right rate, grass would be growing where she sprayed.

Not in the barn lot
“That’s why I don’t empty what’s left in the [sprayer] lines on the first or second rinse in the barn lot,” says Pete Illingworth, a farm crew member who does the spraying at Purdue University's Throckmorton Agricultural Center near Romney.

He could turn the valve and let the liquid flow out, saving time. As it is, he puts rinse water in the tank and heads back to the field to spray out what is left in the sprayer over a nonsensitive crop.

Related:See for yourself why triple rinsing pays

The Miller sprayer Illingworth drives is equipped with an air system that actually blows out the boom lines. He does that in the field, too. “The unit doesn’t spray until I turn on the nozzles,” he explains. “So I can spread it over the field, as well."

"The problem with emptying rinse water in the barn lot is that there is still too much chemical from the spray left in the booms when you are ready to empty out the first batch of rinse water,” explains Fred Whitford, director of Purdue Pesticide Programs. He estimates that on a 120-foot boom, there could be 40 gallons of spray left when the tank is empty. That’s enough to spray at least 2 acres.

Environmental risk
If that rinse water ends up in the barn lot or in one spot in the field, it puts a lot of chemical in one area, Whitford notes. It’s not an environmentally friendly practice. Depending upon the location and proximity to a waterway, it could allow for easy entry of herbicide into a watercourse.

It’s not the right thing to do, and it’s too much risk to take, Whitford says. Someone who continually follows that practice instead of spraying out the rinse water over the field could subject himself or herself to problems. If someone files a complaint for damage to crops or a garden, an investigator from the Office of the State Chemist will visit the site.

If the investigator discovers a location where an operator continually dumps out rinse water containing lots of herbicide residue during his or her visit, whether it had anything to do with the cause of the original complaint or not, the applicator could be subject to a violation.

By the third rinse, the water is virtually clear of chemical. Weed scientists have demonstrated this by spraying water from the third rinse over sensitive plants and noting virtually no damage.