Slowing Herbicide Resistance Evolution

ifr150508–60
Slowing Herbicide Resistance Evolution
Aaron Hager, Extension Weed Scientist - University of Illinois

Weed scientists from the Univesity of Illinois have been trying help farmers manage the inevitable development of herbicide resistance for more than two decades. Todd Gleason reports there is now proof which advice actually works.

Plants are quite capable of evolving…
2:40 radio
2:54 radio self contained

Plants are quite capable of evolving. Weeds like waterhemp have evolved. These weeds are resistant to some of the herbicides used to control them. It was thought, by many weed scientists, this evolution would take place much more quickly with the overuse of any particular active ingredient. So, extension specialists like Aaron Hager from the University of Illinois promoted the rotation of herbicides and modes of action. They didn’t have proof this would work, but now they do with qualifications.

Hager :47 …tank mixed herbicides every time an application is made.

Quote Summary - We realized we didn’t have emperical data to describe the efficacy of the recommendations on a large landscape wide level. A project was started to determine which may be the best methods to slow the evolution of herbicide resistance. For example is it more effective for a farmer to rotate herbicides within a given year or between years? Or is it even more effective to use tank mixed herbicides every time an application is made.

Using the records of a retail applicator the scientist poured through more than 500 site years worth of field level data. The final analysis included 66 variables for each of the fields surveyed for the presence or absence of glyphosate resistant waterhemp.

Hager :14 …present in any particular field, was the management.

Quote Summary - To make a long story short, the analysis showed the most important determination, as to whether or not glyphosate resistance was present in any particular field, was the management.

The management of the field as a whole, not just as it related to glyphosate.

Hager :35 …were made to control a particular population.

Quote Summary - Really the thing that was a bit surprising was that simply rotating herbicides within a year, or perhaps even between years didn’t have any positive affect of slowing the evolution of herbicide resistance. Factually, rotating herbicides year to year showed a higher incidence of resistance compared to areas where multiple tank mixtures were made to control a particular population.

Aaron Hager concludes the best way to slow evolution of glyphosate resistant waterhemp is to expose any given population to more than one effective herbicide every time an application is made.