Iowa State University has warned that Palmer amaranth will wreak havoc on Iowa agriculture. The weed was inadvertently introduced to Greene County by the USDA.
Iowa State University has warned that Palmer amaranth will wreak havoc on Iowa agriculture. The weed was inadvertently introduced to Greene County by the USDA.

December 8, 2016

The effort to slow the growth in Iowa of a weed that devastated the Southern cotton industry took a setback this fall when it became apparent the U.S. Department of Agriculture itself inadvertently spread Palmer amaranth across the state.

Greene County is now one of at least 35 Iowa counties where Palmer amaranth has taken root after landowners enrolled in USDA’s Conservation Reserve Program this spring planted what they thought would be an ideal mix of flowers and milkweed for bees and butterflies.

Instead, it appears the seed was contaminated with Palmer amaranth, the invasive weed native to the southwestern U.S. that could have dire consequences for Iowa agriculture, according to Mark Johnson, a field agronomist for Iowa State University Extension and Outreach.

“Somehow,” Johnson said, “it just inadvertently got in there.”

Johnson said the outbreak can be traced to the native-seed mixes provided to farmers by their local Farm Service Agency, which administers the 30-year-old program in which ag producers agree to take land out of production in order to restore wildlife habitat and help prevent erosion.

The weed isn’t believed to be present in cover-crop seed, according to ISU Extension.

The Greene County Farm Service Agency this week declined to comment on the scope of the contamination.

But even though farmers who got it are hesitant to even be identified, Johnson said it’s not yet a crisis.

If detected early, Johnson said, “They can eradicate it well before it goes to seed.”

Even if a landowner doesn’t manage to eradicate it, the majority of seeds that drop will be contained to acres off limits to farming.

“The majority will stay in that field,” he said. “It hasn’t evolved to spread by wind.”

The concern is that the seeds could find their way to crop fields.

“Then it’s very competitive with the crops,” Johnson said. “It’s way more competitive than any weed we’re used to.”

Now that it’s here, identification is the next line of defense.

Johnson was expected to be in Jefferson on Thursday morning to help farmers identify Palmer amaranth and establish best-management practices for it.

Greene County Extension had been approached by the FSA about hosting an informational meeting at Clover Hall, said Lori Mannel, county Extension director.

She wasn’t sure what to do last week with the sample of Palmer amaranth in her office that a local farmer brought in for the meeting.

“It’s duct-taped and double-bagged,” Mannel said, describing something akin to ebola. “I just put it in the corner and haven’t touched it.”

A summer annual, Palmer amaranth has been in Iowa since 2013, when it first was detected in five counties.

Harrison County was Iowa’s ground zero.

It most likely arrived via out-of-state farm equipment, according to ISU Extension.

There were no additional reports in Iowa of the weed until this year, Johnson said, when it began showing up in newly seeded conservation plantings in more than 30 counties.

Even before the extent of the contamination was known, ISU Extension in August warned that a spread of Palmer amaranth across Iowa “will have a huge negative economic impact.”

Johnson said he’s gone on three or four calls in Greene County to identify Palmer amaranth.

One Carroll County farm he visited where the farmer hadn’t mowed his CRP acres, per the agreement with FSA, had a lot of it.

And it was huge.

“He’s going to have way more next year,” Johnson said.

There are reports of the weed in Minnesota as well, he said.

It’s difficult to trace the source of the contaminated seed, he said.

“I’ve been teaching about Palmer amaranth for five or six years, saying it’s not if we get it but when we get it,” Johnson explained.

Johnson said he never thought it would arrive in Iowa this way.

“I thought it would be a county this year, then a county or two next year,” he said.

It’s unknown if the Palmer amaranth in Iowa is resistant to chemicals, Johnson said.

In the South, where the weed can result in yield losses of 80 percent, it’s evolved to be resistant to herbicides.

Johnson’s recommendation is to eliminate it one plant at a time.

“You have to walk the field,” he said.

Johnson said Iowa State’s advice this summer for removing mature plants was to dig them out with a shovel, then drive them off the property and burn them.

Palmer amaranth is related to waterhemp — which already is common in local corn and soybean fields — but is more aggressive and grows faster.

Greene County farmer Pete Bardole, a newly elected county supervisor, has been at war with waterhemp since the early 1990s.

“One plant makes thousands and thousands of seeds,” Bardole said, “and they’re tiny.”

In November, he planted 45 pounds of CRP seed on 5 or 6 acres.

By then, the seed was supposed to be free of Palmer amaranth.

Still, he won’t know for sure until spring.