Aggressive weed causes headaches for Midwest farmers

By Ryan Carpe rcarpe@civitasmedia.com

March 29, 2014

DARKE COUNTY - Palmer amaranth. No, it’s not a tongue twister, but an invasive, agressive pigweed that is slowly creeping across the Midwest.

Originally native to desert regions of the southwest United States, the plant has slowly taken a major foothold in the southeast and has plagued cotton and soybean farmers ever since.

Recently, Palmer amaranth has been confirmed in Ohio, Indiana, Michigan and Illinois, signalling a bad omen for local farmers.

“We do have several confirmed patches of it in the state already, so its just a matter of time if we can’t get ahead of it,” said Sam Custer, Extension Educator for Agriculture and Natural Resources in Darke County.

Specifically, Palmer amaranth has been identified near Washington Court House and as close as Mercer County. In the case of Mercer County, only one plant was found and confirmed, and it has since been incinerated.

Currently there are no confirmed cases in Darke County.

Palmer amaranth is thought to have migrated through the transportation of farm equipment and feed sources, which can be transported throughout the entire country.

If Palmer amaranth did gain a major foothold in Darke County, farmers would potentially have to triple their herbicide costs to try and control the outbreaks. If those costs become frequent, it could easily account for a farmer’s already slim profit margins.

Farmers in Darke County and nearby regions are used to fighting breakouts of common mare’s tail or ragweed in their fields, but according to the Darke County OSU Office, palmer amaranth is much more severe.

“(Mare’s tail and ragweed) are a real challenge. A lot of times they’ll affect the yield some. But they’re not anything like this palmer amaranth,” said Custer.

For one, palmer amaranth can have more than half a million seeds per plant, whereas mare’s tail may have 5,000 seeds per plant.

“It could be a neighbor’s problem this year and next year it could be your problem, because of birds, wind and other factors moving it,” said Custer.

Not only does the weed propogate at an alarming rate, but Palmer amaranth is highly resistant to many common forms of herbicide, including ALS inhibitors, triazines, HPPD inhibitors, dinitroanilines, and glyphosate.

“There’s farmers that have abandoned whole fields because its resistant to so many herbicides. It grows so fast, and its just really terrible to control,” said Sam Custer.

According to the Purdue University Extension Office, the majority of populations in the South are ALS-inhibitor- and glyphosate-resistant.

But that’s not all.

Palmer exhibits aggressive growth and competitiveness with crops.

Under ideal conditions, Palmer amaranth plants can grow two or three inches per day, while causing potential yield losses of more than 90 percent in corn and up to 79 percent in soybean according to recent studies.

The first step to stopping an outbreak is early detection, which often requires visual knowledge of the aggressive weed.

Palmer amaranth leaves are wider and ovate to diamond-shaped, they have no hairs on their stems and leaf surfaces, and its petioles will be as long then the leaf blade itself.

Palmer amaranth is also often confused with three other similar-looking amaranth species: redroot pigweed, smooth pigweed, and common waterhemp.

As soon as the weed is identified, the Ohio State University and extension offices would collaborate on an all-out effort to remove the invasive species as quickly and efficiently as possible. Initially an OSU weed specialist would arrive to identify and confirm the plants and collect samples for testing.

From there, OSU specialists would either dig up the targeted plants and incinerate them or develop an herbide plan to bring it under control.

“The farm community is watching for it,” said Custer. “Anybody that’s out needs to keep their eyes open for it.”

For additional questions about palmer amaranth or to report an outbreak, readers can contact the Darke County OSU Extension Office at 937-548-5215.