Monday, March 21, 2011

Herbicide resistance

Herbicide resistance in weed species
By Mark Watson, Panhandle No-Till Educator
The Fence Post
March, 21 2011

A growing concern across the country is the development of herbicide resistance in weed species to glyphosphate herbicide more commonly referred to as Roundup. This herbicide has grown in popularity in crop production since it first came on the market years ago. With advanced technology we now have crops such as soybeans, corn, sugar beets, and alfalfa which tolerate the herbicide. These genetically modified crops can be planted and the glyphosphate herbicide applied on them to control weeds in the crop.

The widespread use of glyphosphate herbicides has in some incidences led to development of weed species that have developed resistance to its use. I listened to Neil Harker, a weed specialist from Canada who gave a presentation at the No Till On The Plains winter conference on this topic.

Mr. Harker showed the areas around our country where resistance to glyphosphate has developed in certain weed species. As you would guess, the biggest concerns are in the corn and soybean growing regions where producers are using a Roundup ready corn/roundup ready soybean rotation on their farms. In this region of the country there are now several weed species that are resistant the glyphosphate herbicide.

We are at risk here in the Panhandle to developing weed resistance to glyphosphate herbicide on our farms. We have widespread use of Roundup ready corn and sugar beets. Many of us also use Roundup as a burndown prior to planting crops which aren’t Roundup resistant such as edible beans, winter wheat, field peas, sunflower, millet, etc. There is also widespread use of Roundup with producers who are using chemical fallow in place of tillage fallow in winter wheat production.

I think it is in our best interest if we develop management strategies to combat the overuse of this herbicide so glyphosphate remains a viable herbicide in our crop production practices. I think the best management practice we can use is proper crop rotations which allow us to vary the herbicide, timing, and mode of action in the herbicides we use to produce our crops. Proper crop rotations with the use of pre-plant and post-emergence herbicides with residual activity will allow us to reduce the number of applications of Roundup or glyphosphate we use in our crop production systems.

On our farm we are developing herbicide programs which will limit the use of glyphosphate in our no-till crop production system to no more than one application of glyphosphate per year on any field. We plan to incorporate herbicides in our program that have enough residual to reduce the spraying of glyphosphate to no more than once a year and in some cases we can go even longer without the use of this herbicide. I think this strategy will greatly reduce the risk of developing weed resistance.

If you are using Roundup ready crops such as corn or sugar beets try to develop herbicide programs which also reduce the amount of times you apply the glyphosphate herbicide. For those producers who are using glyphosphate herbicides rather than tillage in their wheat/fallow systems I would encourage you to change your herbicide program or cropping system. Possibly replace this long fallow period with a crop rotation or a cover crop which would reduce the amount of glyphosphate herbicide you are applying on your fields.

We need to pay close attention to our herbicide programs that include the use of glyphosphate herbicide and reduce the amount of times we apply this herbicide as much as possible. Glyphosphate herbicides have proven to be excellent herbicides for our crop production systems, but we need to use this herbicide in a prudent manner which will insure the effectiveness of this herbicide for the future.

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