Herbicide Resistant Weeds

South East Farm Press recently published an article about the damage herbicide resistant weeds can do.  A four year study by Weed Science shows how devastating a single herbicide resistant weed can be to a crop field.

The research covered fours years and four different fields of cotton in Arkansas.  In the study, 20,000 seeds of glyphosate-resistant Palmer amaranth was released into a field and untreated and allowed to escape.

In one of the fields there was a total crop failure.  This shows the need for a zero-tolerance threshold when it comes to weed management.

Seeds can be spread by wind, water, animals and humans.  Seeds such as palmer amaranth can float on top of water causing it to spread rapidly in a field.  Palmer amaranth has prolific seed production rate, rapid dispersal and high competitiveness with crops making it very difficult to control.

In the Arkansas study, only glyphosate herbicide was used.  In the first season, a patch of Palmer amaranth grew 375 feet from the original planting location.  In the second season, the weed reached the field boundaries and infested 20 percent of the field area causing a significant yield decline.  By the third season, the weed had completely covered the field, making it impossible to plant any cotton.

This study easily shows how using only one form of herbicide can be ineffective when it comes to defending your farm from weeds, especially Palmer amaranth.  It also shows the need to keep all resistant weeds in a controlled area.  Weed control based on an economic threshold does not adequately consider the soil seed bank and the risk for herbicide resistance.