Resistant Pigweed populations present new obstacles

When managing resistant Palmer pigweed in your fields this season, the density of populations are more important than you may have thought. A recent article in the Delta Farm Press called “High incidence of glyphosate resistance in Arkansas pigweeds” highlights research at the University of Arkansas by researchers Ken Smith and Ryan Doherty.

Smith says there are often distinct patterns of Palmer pigweed populations in fields. When the plant populations are scatted through the field, some plants may show some affects to glyphosate, but not enough to eliminate them.

When plant populations are very dense, (over 100 per square yard), regardless of the glyphosate rate, even up to eight times the recommended amount, the population will not be damaged. Dense populations in small portions of the field point to a single resistant female plant from the previous season. Smith advises to do what ever you can to eliminate this population, even if you have to do it by hand.  

The good news is Palmer pigweed is that the seed rarely exists for more than two years; the bad news is the large amount of seed one plant can produce. With the severe yield impact Palmer pigweed can have, using and implementing existing management tactics becomes increasingly important, especially with no new chemistries or techniques on the horizon. Click here for more information about selecting the best management practices for your field. For more information about managing glyphosate resistant pigweed in the South click here. For corn and soybean growers, visit the RF solutions model to easily find a management plant for your farm.