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Screening for HR Weeds

I direct your attention to a Sep. 1, 2023 article titled “Arkansas rice: 8 tips to collect herbicide-resistant weed samples” by Whitney Haigwood that appears in Delta FarmPress. The contents of the article deal with the details of a herbicide resistance screening program at the Univ. of Arkansas that is available to the state’s rice producers.

This article got me to thinking about the following points.

•    Herbicide resistant [HR] weeds have become commonplace in all Midsouth crops that include soybean, corn, rice, and cotton.

•    If a soybean producer suspects a particular weed species has developed resistance to a class of herbicides, he/she needs verification of that occurrence in order to 1) select a herbicide in a different class that may control the HR weed, or 2) select a variety that has tolerance to a class of herbicides that will control the HR weed when a herbicide in that class is applied post-emergence.

•    This then leads to the following questions. 1) Why don’t the Midsouth states have programs that offer screenings for suspected HR weeds that occur in soybean fields within their boundaries? 2) Better yet, why can’t there be a regional screening program that is available to all soybean producers in the Midsouth states?

•    Such programs could be 1) funded within each state using checkoff monies that are allotted to researchers who submit proposals for the funding of such a project, or 2) on a regional basis, where such a program could be funded as has been done in the past where each state contributes a certain amount of funds for an approved regional project.

•    Since the states of Arkansas, Louisiana, Mississippi, Missouri, and Tennessee all have a sizeable acreage of corn, cotton, and soybeans, and all except Tennessee have a significant acreage planted to rice, it seems plausible that such a regional project should be considered for funding using checkoff monies collected from those crop producers.

•    Since soybeans comprise the largest acreage of any of the above crops in each of the above states, it seems plausible that such a program to identify HR weeds in soybean fields could be funded with soybean checkoff monies.

It is unlikely that a crop producer can definitively identify an HR weed based on that weed not being killed by a particular herbicide that was applied to it. Only by having a program that uses a valid and consistent research approach to verifying herbicide resistance in a particular weed from a particular location can that weed be verified as being resistant to a particular class or classes of herbicides. Now seems the time to initiate such a screening program in the Midsouth so that soybean producers in that region can verify herbicide resistance in uncontrolled weeds. This would certainly be an important step in the fight against increasing HR weed development.

Composed by Larry G. Heatherly, Sep. 2023,