Weed resistance to chemical herbicides is big topic getting bigger among farmers this year in the Dakotas and Minnesota. Officials are urging people buying seed mixttures for pollinator or wildlife habitat to know the source, and whether it can can carry “pernicious and devastating” weeds including Palmer amaranth.”
“It is apparent that glyphosate-resistant waterhemp and ragweed continues to spread in North Dakota, despite the conscientious efforts by growers, industry and academia, said Richard Zollinger, a North Dakota State University Extension Service weed specialist, in a Sept. 16 e-mail warning.
Farmers and their advocates are wondering how it’s possible for the weeds — primarily waterhemp — to expand so fast, and wondering how they’re spreading so fast.
Zollinger notes that Bob Hartzler, a weed scientist at Iowa State University, has seen Palmer amaranth infestations have increased from “five counties to 30 counties!!!” this summer.
“The pollinator habitat is probably the most common seed source with contamination, but it has also shown up in feed plots (or whatever hunters call the habitat they establish for bird cover),” Hartzler says. “I think any mix of native species is a potential culprit.”
Weed-contaminated seed mixes have come from “numerous” seed suppliers, Hartzler says. “Some of the seed tags stated 0.00% weed seed. In our studies we have found pigweed seed in the process of determining if Palmer seed is in the mix. Support to determine who planted this type of seed mix has been variable. Some counties have been very supportive; others are not.”
Zollinger says that the infestations in the northern tier of counties are very close to Minnesota, which “supports the likelihood of Palmer amaranth infestations from mail order seed sources.”
Greg LaPlante, a Wahpeton, N.D., crop consultant who has advocated techniques to stop the spread of herbicide-resistant weeds, said he had talked to an Ames, Iowa, farmer who had confirmed Hartzleer’s report. “Wildlife and pollinators habitat groundd showed up with alarming levels of Palmer,” LaPlante said. “He planted 100 acres and he never had Palmer and that is the field he has infested.”