Stop weeds in their tracks

Weed seeds can be moved from location to location in a variety of ways — by animals, wind, and water. The most common, however, is by catching a ride on equipment that travels among fields. 

One way to slow the spread of weeds is to perform regular combine cleaning, says Dan Smith, southwest regional agronomist at the University of Wisconsin-Madison. 

“I know it can be hard to justify taking 30 minutes out of a harvest day to stop and clean your combine,” he says. “But our research shows that you can spend up to $80 per acre controlling troublesome weeds like Palmer amaranth. You can quickly see the benefit.”

While a thorough top-to-bottom cleaning of the combine is important on occasion, Smith found that good weed seed control can be achieved by focusing on a few key areas. 

“We most commonly saw weed seeds on the grain platform or head, moving into the feeder house, and the rock trap. Most weed seed doesn’t make it into the clean grain system unless (the seeds are) really large,” he says. 

His tool of choice is a cordless leaf blower. Most major tool manufacturers offer one. Gas powered leaf blowers also work, and if you have the option of an air compressor, “that’s the Cadillac,” he says.

He recommends cleaning in the spot where the weeds are. If there are only a few weedy spots in the field, he suggests stopping to clean there after you go through them. 

“Those weed seeds are going to spread to other parts of the field, so if you just have areas of weeds you might consider cleaning as you go,” he says. 

The cleaning process should take around 30 minutes or less, Smith says. After putting on an N95 or P100 respirator, safety goggles, and following your machine’s safety guidelines for locking the head and other precautions, start by cleaning the head with your leaf blower. Then dump the rock trap, which is where most weed seeds end up. 

“If you’re moving to a new field, and can take off the head, clean out the feeder house by blowing air in through the access panels,” he said. “The feeder house is the only area on a combine where we’ve actually seen weed seeds germinate and grow. Seed trapped in the feeder house is why we often see weedy patches at the entrance of the field, when they get bounced around and sent back out.”

Smith says you don’t need to take the extra time in the field to clean the rotors and clean grain elevator system, as his research showed fewer weed seeds in those areas. If it is critical to clean the entire machine, he says running wood shavings through the combine is a quick and safe way to accomplish that. 

“If you stick to the front sections of the combine, in about 30 minutes you can knock off an estimated 80 to 95% of weed seeds,” Smith says. 

Cleaning regularly also helps with safety, as there is less residue to become a potential fire hazard.