At a recent agAcademy at the Monsanto research farm in West Lafayette many growers got their first look at Palmer Amaranth, or Palmer pigweed. It is a weed than has migrated from the south and is becoming more prevalent in Indiana.
In a special HAT video (below) Dan Childs, Technology Development Representative at Monsanto describes the most recent threat to Indiana soybeans.
“It is a glyphosate resistant weed. It is in the pigweed family. It is very prolific and probably the most competitive of any of the pigweeds, more competitive than even waterhemp which is another pigweed. Very characteristic of Palmer is a very long spike that can reach 4 feet in length. The total plant height can get 7 feet or taller. We had a Palmer pigweed in that corner of the field this year. We have since cut it down with a chainsaw it got so big.”
Childs says that plant was growing 2-3 inches each day and the female can produce up to a million seeds per plant. Is there control for the weed?
“Fortunately we still have tools that can help control Palmer today. The residual herbicides Warrant, Valor, Authority, those will give you pretty decent control, but once they get above 4 or 5 inches tall it’s really hard to control them.
Becca Holt says Palmer that is cut down then needs to be destroyed. If it is left lying in the field it will go to seed. She is now getting more and more inquiries about the weed and stories about how hard it is to control.
“I had one story last week and another one this morning where individuals used residuals up front and came back in with Roundup and another residual, but they had some wet spots in the field that they didn’t get to. They now have patches of this growing in those wet spots. I’ve been getting text messages asking what is this weed, so we need to identify it and get it under control.”
Childs says one of the best control methods for Palmer pigweed in a soybean field is to switch the field to corn for several years and let the corn herbicides kill it off. The most recent report from Purdue’s Bill Johnson says as of Thursday afternoon the weed has been located in 20 Indiana counties.