To Prevent Weed Seed Spread With Your Combine

On October 05, 2020

To Prevent Weed Seed Spread With Your Combine


An ounce of prevention is worth a pound of cure when it comes to weed management—especially for herbicide resistant weeds. Resistant weeds cause significant yield loss and increased production costs and are becoming a bigger problem every year in Pennsylvania.


Our most problematic herbicide resistant weeds, like marestail, waterhemp, and Palmer amaranth, can easily spread from one field or one farm to the next, as seeds get trapped in the combine and hitch a ride field-to-field at harvest. So Extension Agronomists Heidi Reed and John Wallace explain it is important to be proactive to prevent this seed spread. You should have a plan going into the harvest season, including the appropriate order to harvest fields, and equipment-cleaning protocols. GROW, a publicly-led network that provides resources and tools for implementing integrated weed management (IWM), suggests a few simple ways to prevent the spread of weeds with equipment.


The first step is to scout fields before harvest, and identify which fields have noxious weeds. Then harvest and/or till herbicide-resistant weed-infested fields, or portions of fields last. If the combine or tillage equipment entering a field has recently been in a field with herbicide-resistant weeds, clean the equipment, or use different equipment if it is available. Carefully and completely clean used equipment upon purchase. Start cleaning the combine from the top, and moving from the header backward. Use an air compressor to remove as many weed seeds from the combine as possible, including the rock trap, grain auger and tailings processor. Deep clean the combine following the Straw Bale Methodology: (  when moving from fields infested with herbicide resistant weeds, and at the end of the year.

You can read more, including a case study about waterhemp movement in southeastern Pennsylvania, here:


Once harvested, fields should not be abandoned until next spring. Marestail, a winter annual weed, will thrive in the fall after corn or soybean harvest; fall burndown in marestail-infested fields is essential.


And, although waterhemp and Palmer are summer annuals, they can still potentially set seed with favorable weather, even if the cutter-bar knocked them back to only a few inches tall. It is important to continue to scout fields and take action if necessary.


Lastly, planting cover crops after any necessary burndown this fall can substantially improve weed management. Research shows that high-biomass cover crops, like cereal rye, can not only reduce the number of weeds that emerge from seed in the spring, but delay weed germination and growth, making it easier to spray while weeds are smaller and more susceptible to herbicides. A thick cover crop mat can extend this weed suppression well into the growing season.


Preventing weed spread is an important tool in the integrated weed management (IWM) toolbox, and cleaning equipment is worth the time and effort today to prevent a serious management challenge in the future.


To Prepare Grain Storages For Harvest


As we approach corn grain harvest, Extension Agronomist Anna Busch and Extension Entomologist John Tooker remind us to properly prepare grain storages. Several species of beetles and moth caterpillars can attack stored grain. Once insect infestations are established, they are difficult to control, so a good mindset is “start clean to stay clean.”

Sanitation is the most effective way to prevent stored grain pests. Before adding new grain to a storage, remove all old grain, which may be a source of insect populations that can rapidly infest the new grain. Clean the walls and floor by sweeping, vacuuming, or washing. Inspect and clean dust around doors, seams, vents, and false floors. Repair any cracks or holes in bins.

Do not forget about inspecting the areas around grain bins. Remove any old grain that has collected around the outside of the storage. Mow or remove any grass and weeds around the storage structure. Harvest equipment should also be inspected for lingering, old grain and cleaned before being used.

After bins have been properly cleaned, storages can be sprayed with a residual insecticide. Bins should be sprayed at least 2-3 weeks before being filled with grain. For long-term storage, grain protectants can also be added to the grain as the bin is being filled. Refer to the Penn State Agronomy Guide for details.

Because corn cribs are open, insects are especially difficult to control and fumigation is not an option. Corn cribs should be cleaned properly each year. Never add new grain on top of old grain. Residual sprays and grain protectants may provide some control if corn is being stored long-term.

Remember pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams, or ponds.


Here are more resources from Penn State:

Management of Stored Grain Pests in Organic Systems:,

Managing Stored Grain on the Farm: and Preventing Stored Grain Pests:


Quote Of The Week: “Children are natural imitators. They act just like their parents in spite of the effort to teach them good manners.” Amish Proverb by Suzanne Woods Fisher