Southern farmers have met their enemy and it is Palmer amaranth. “Palmer pigweed is diabolical,” says Chuck Foresman, Syngenta’s manager of weed resistance strategies. “It’s hard to believe, but 54% of the cotton in Georgia was hand weeded in 2009.”
Midwestern growers now know Palmer amaranth’s ugly cousin, waterhemp, all too well. This summer, the troublemaker was found resistant to the fifth class of chemistry. Waterhemp resistance to a post-emergence HPPD inhibitor herbicide was confirmed in a seed corn production field.
“The case was isolated, but it is a good example of how these weeds can evolve,” says Foresman. “It was caused by a lack of diversity in use of herbicide modes of action, crop rotation and method—we can no longer depend solely on post emergence products.”
Watch those wet spots. Foresman says drowned out spots throughout the Midwest are filled with waterhemp. Resistant marestail and ragweed are already causing issues in many parts of the country. Johnsongrass, barnyardgrass, common lambsquarters and Russian thistle are other weeds on his weed resistance radar.
Foresman points to a survey of farm managers, rural appraisers and crop consultants in August of 2010 that estimates yield losses to glyphosate resistance at 5.5%. The same group estimated the problem required $16.90 per acre in additional management and herbicide costs.
“Glyphosate is the most important herbicide ever invented. Of the 170 different weeds it controls, 11 now have resistance issues. It’s time we start doing what we can to extend the life of this valuable tool. The key to that is developing an integrated weed management program includes a preemergence product with residual that keeps those weeds from emerging in the spring,” Foresman adds.
Listen in as Chuck Foresman talks weeds and weed control.
Find more information on specific products at www.resistancefighter.com. Find a complete list of resistant weeds at www.weedscience.org.
