Palmer Amaranth In 49 Iowa Counties, Up 10X From 1/16; Glyphosate Effective So Far . . .
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U.S. agriculture agencies are working with ISU, the state and other agencies to determine what actions landowners can take on conservation fields. Owners of Midwestern land where the weed has been introduced through conservation seed mixes have run into complications trying to control it.
While Hartzler's testing isn't conclusive, he was able to kill Palmer amaranth grown from conservation field seeds with glyphosate, the active ingredient in Roundup, the world's mostly widely used herbicide. That gives Iowa an advantage over southern states, where the weed is resistant to several herbicides, including glyphosate. It has forced growers there to frequently till fields or hoe weeds by hand. Some farmers have illegally used a herbicide not designated for spraying crops mid-season in a desperate attempt to control the weed.
The unintended drift damaged crops on thousands of other acres, including peaches, tomatoes and other sensitive produce, said federal officials, who are investigating.
Even if Palmer amaranth can be killed with herbicides in Iowa, it can't be wiped out when the fast-growing plant reaches a certain height, making it extremely hard to control. And using glyphosate would kill more than Palmer amaranth in native prairie fields, planted with sunflower, coneflowers and other forbs that help feed monarch butterflies, bees and other pollinators whose populations are threatened by dramatically reduced forage.
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http://www.desmoinesregister.com/story/money/2016/12/15/invasive-super-weed-spreads-through-iowa/95037406/
