John Gricius had only seen pictures of Palmer amaranth. So last July, he decided to take a look for himself by attending a northern Illinois field day held near his farm.
What he found was his worst weed nightmare. "I've never seen weeds that thick," said the Manteno, Ill., farmer. Palmer amaranth towered over corn and smothered soybeans in the plot. University of Illinois and Bayer CropScience weed scientists have been using this piece of land near Kankakee, Ill., as a testing ground to see how Palmer amaranth behaves and what weed control practices work best in the Midwest. The weed population was discovered growing naturally at the site two years ago, about 75 miles southwest of Chicago.
Tough-to-control weeds coupled with their ability to resist popular herbicides dominated the agronomy scene in 2014. Palmer amaranth, the scourge of the South, became well-established in states where growers desperately hoped it would never grow. Purdue University weed scientist Bill Johnson told DTN Palmer amaranth has spread to nearly every corner of Indiana. "We now think we were misidentifying a lot of waterhemp that was really Palmer," Johnson said.
Meanwhile, waterhemp also continued to romp across the landscape. The weed capitalized on gaps in fields hammered by weather in Iowa and Nebraska. Missouri captured the dubious honor of having the first confirmed waterhemp population with resistance to five different classes of herbicides (glyposate, HPPD, PPO-Inhibitors, PS II-Inhibitors, ALS-Inhibitors). More multiple resistance and cross-resistance issues cropped up and the message that no "new" chemistries are coming in the near future intensified from the chemical industry.
To fight back, farmers reached for more residual herbicides and sequential residual applications in an attempt to plant clean and not rely on post-emergence rescue treatments. However, cost-cautious farmers are concerned about this spring as commodity prices leave little cushion for pricey inputs.
University of Tennessee weed scientist Larry Steckel said from 2006 to 2014, growers in his state saw the cost of corn herbicide controls grow to $60 to $70 per acre compared to $30 per acre. Soybean herbicide control has risen to $80 to $100 per acre, compared to $30 per acre during times of Roundup Ready dependence. Cotton farmers are experiencing herbicide costs of $100 to $120 per acre today, versus $60 per acre in 2006. Southern growers are also spending an additional $25 to $30 per acre for hand chopping crews, he said.
Purdue's Johnson polled a crowd of growers and custom applicators about herbicide costs during a meeting in Illinois in mid-December. The average cost for herbicides only in the Midwest was estimated at $60 per acre, compared to $30 to $40 per acre pre-glyphosate resistance.
An intense weed education campaign called "Take Action" (www.takeactiononweeds.com) sponsored by universities, industry and commodity associations identified the "11 to Threaten" weeds in the U.S. as: common waterhemp, Palmer amaranth, marestail (horseweed), giant ragweed, common ragweed, common lambsquarter, Johnsongrass, kochia, Italian ryegrass, barnyard grass and giant foxtail.
Still, it's the rapidly growing Palmer amaranth that seems to be driving the message home to growers such as Gricius. The long-term message for 2014: Farmers must begin once again to understand weed biology and herbicide interactions to manage weeds rather than simply kill them.
Source: www.dtnprogressivefarmer.com