Glyphosate contributes the biggest slice to feed resistance

Without looking at a field, one could predict that too much of one thing can’t be good. Glyphosate-resistant weeds in the U.S. did not exist before 1996. By looking at the herbicide chart demonstrating the use of various chemicals used in 1996 vs. today, diversity was a much bigger part of managing weed populations. By altering chemistries and keeping the herbicide portfolio diverse, weeds had much less of a chance to develop resistance to one particular herbicide.

In 2007, the chart to the right, tells us a very different story. Growers have changed management practices due to the simplicity and economics of glyphosate-tolerant systems. An increased number of soybean fields are only sprayed with glyphosate, and reliance on other chemistries has become negligible. In comparison, the number of glyphosate-resistance weeds that have developed as reliance shifted to one herbicide has increased dramatically. Marestail (horseweed) was the first glyphosate-resistant weed in soybeans in 2000. Today, there are 9 resistant species confirmed in 20 states.

In order to protect glyphosate technology and curb the spread of resistant weeds, the right management practices must be implemented.

What do you do on your farm to manage resistance? How will the increased cost of glyphosate this season affect your herbicide choices, and as a result, your resistance management tactics?