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A Good Way to Kill an Acre of Corn

15:04PM Jul 15, 2013
Isaac Ferrie Photo of Weed Presentation

You can lose $1,000 easily by not cleaning your spray system adequately

In the Roundup world of weed control that most of us use to live in, cleaning out your sprayer and boom was no big deal--if you did, great, but if you didn’t, no harm done. Those days are probably over, according to Isaac Ferrie, agronomist for Crop Tech Consulting, Inc.

The need to use multiple herbicides to control weeds today means you also need to clean your spray system thoroughly between applications and track what product is sprayed where.

Otherwise, Ferrie explains: "Say you don’t clean a 90-foot boom adequately and it still contains herbicide, you have the potential to damage or kill up to an acre of corn." Cost-wise that loss easily adds up to $1,000, based on a 200 bu. per acre yield at a price of $5 per bu.

Ferrie spoke on the topic of herbicide management to improve farmers’ weed-control results during the 2013 Farm Journal Corn College near Heyworth, Ill.

Protect Yield Potential

As part of Ferrie’s discussion, he talked about the differences between herbicide modes of action and sites of action.

He says site of action is a phrase farmers can expect to hear weed-control experts refer to more often in the future. While the industry often uses the terms site of action and modes of action interchangeably, there is a distinct – and important – difference between the two.

"Mode of action tells us what effect the herbicide will have on the plant," Ferrie explains. "Site of action tells us what pathways the herbicide will use to inflict that damage."

Some additional key takeaways from Ferrie’s presentation on herbicides:

  • The goal in preventing weed resistance is to regularly change what pathways are being attacked within the plant by choosing chemicals with different sites of action;
  • By choosing different sites of action, the mutated or resistant plants can be killed before they reproduce, stopping resistance from spreading;\
  • It is important to note that choosing chemicals with different active ingredients is not enough; you must make sure that your rotation of chemicals contains varying sites of action;
  • In an attempt to change up their mode or site of action, applicators and farmers are going to be using products that have not been all that common in the past decade. This could lead to an increased number of herbicide complaints as drift and carryover issues become more of a problem.


Much of the information you need in order to select herbicides with different modes of action and sites of action is readily available online from most state university Extension weed science departments. Find your Extension specialist.


Thank you to the 2013 Corn College sponsors:

AgriGold, BASF, Chevrolet, ESN/Agrium, Great Plains, Honeywell, Koch, Novozymes, Precision Planting, SFP, Top Third Marketing

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