Preventing Spread of Weed Seeds from Field to Field this Fall

With the weeds observed in some fields throughout the area, preventing weed seed from spreading into clean fields should be an important part of harvest.  An ounce of prevention can keep weed issues in problem fields from spreading into clean fields.  While typically you want to hand pull or hoe weeds out of fields where only a handful of plants exist, this will not be a viable method for many fields this year.  This means the destination for that weed seed is to be run through a combine and potentially spread wherever that combine roams.  Combines can easily carry 150 pounds or more of bio materials (including weed seed) in various locations throughout the machine from field to field. So, it is important to take steps to help prevent that spread from field to field.  To help prevent that spread here are some things to consider when combining this fall. Nathan Drewitz, University of Minnesota Extension, provides the following considerations.

Preventing weed seed spread prior to combining is always preferable. So, where possible remove problem weeds.  For those fields where weeds are too many to hand pull, consider harvesting those fields last to help prevent the flow of weed seed to clean fields.  Also, take time to properly clean your combine between fields especially if you are coming out of a field with weed issues present.  Specific areas to focus on include the header, feederhouse, rocktrap, grain tank, and unload auger.  The following 20 to 30 minute procedure is from a publication by the North Central Extension Agriculture and Natural Resources Academy’s Combine Clean Out series which can be found here:

  1. Run unloading auger empty for at least one minute.
  2. Open the clean grain and tailings elevator doors, rock trap, and unloading auger sump.
  3. Start the combine and separator.
  4. Operate the combine this way for at least two minutes for self-cleaning.
  5. Clean any material left in the rock trap.
  6. Use a leaf blower or air compressor to remove material from exterior of the combine focusing on the header, feederhouse, and axle and straw spreader at the rear of the machine.
  7. Remember to close the doors to the rock trap, clean the grain elevator, and the unloading auger sump.

The recommended tools for cleanout are usually a vacuum or compressed air.  If a pressure washer is used some of the residues may become sticky and harder to remove.  Also, always make sure to use the proper Personal Protective Equipment which includes gloves, protective eyewear, a dust mask with at least an N95 rating, and hearing protection.


Written by: Bill Halfman, Extension Monroe County, Agriculture Agent, email:

For more information, please contact:
Carolyn Ihde, Agriculture Agent, Extension Richland County by email:

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