Arkansas and Resistant Palmer Pigweed

In a recent trip to Arkansas, renowned weed resistance expert Dr. Paul Neve, along with University of Arkansas Extension weed scientists and Syngenta weed resistance experts, attempted to study the growing threat of glyphosate-resistant Palmer pigweed plaguing Arkansas corn, soybean and cotton growers.

As more weeds in Arkansas develop resistance to glyphosate, management changes must be made.  Although Neve believes growers can still manage and find new ways to produce healthy yields, the process undoubtedly becomes more difficult once weed resistance enters the picture.  This is where it pays to practice resistance management before the problem exists.  For instance, one of the findings in Arkansas was that the worst glyphosate-resistant Palmer pigweed areas are those that first began using glyphosate technology.  Using this logic, areas that began using glyphosate shortly after have a high risk of developing resistance due to the prolonged use of glyphosate herbicides on those acres.

In addition to rotating both crops and chemicals on the fields, it is recommended to use full, labeled rates in order to reduce the chance of weeds to develop resistance.  For many years, a large majority of Arkansas growers have been using reduced rates to save time and, most importantly, money.  Due to the rising number of glyphosate-resistant weeds spreading across the state, extension scientists have taken reduced rate program recommendations out of their literature and now tell growers to use full rates to guard against resistance.

Using reduced rates may save time in the moment, but the cost of dealing with resistant weeds can be far more expensive.  Reduced rates may kill the weeds at first, but it is easier for a weed with a resistant gene to survive the low dose, grow, germinate, and produce resistant seed. Even if the probability for resistance in a population is low, if a plant produces a high number of seeds and conditions are conducive to resistance development, it doesn’t take long for it to become a real problem.

Sometimes, however, weeds can develop resistance even when these practices are implemented.  Do you think it is worth the extra money and time to start following these recommendations now, or do you think weed resistance is something that shouldn’t be a concern unless you are experiencing it already?  What reasons support your thinking?

For the full Arkansas weed resistance article in the Delta Farm Press, click here.