Weed Management: Pre-Emergent Control Necessary for Pigweed – Video

Purdue University weed scientists have developed two time-lapse videos capturing the rapid growth of Palmer amaranth and the effect of pre-emergent herbicides used to control the aggressive and destructive weed.

The videos were compiled from footage shot last year at the Purdue weed science research site in Cass County.

“After viewing these videos, the message we want to get across to producers is the utility of using a pre-emergent herbicide,” said Travis Legleiter, Purdue weed science program specialist.

The first video presents a side-by-side view of two soybean plots. One plot was treated with a pre-emergent residual herbicide and the other was untreated.

The video shows Palmer amaranth quickly growing to an unmanageable size and encroaching on the soybeans in the untreated field while the treated field remains mostly clear.

“This shows why using a pre-emergent herbicide is so important to get the weeds at their weakest point,” Legleiter said. “The control of post-emergent herbicides dramatically decreases once the Palmer amaranth plant is taller than 4 inches.”

The second video shows how quickly Palmer amaranth grows and spreads once it is established.

“One thing we don’t talk about a lot is biomass,” Legleiter said. “Palmer amaranth plants get tall, but they also get wide, taking up a lot of light and crowding out other plants.”

Legleiter worked with Bill Johnson, professor of weed science, to produce the videos. The team produced an earlier video showing producers how to identify Palmer amaranth, which was first identified in Indiana in 2012.

Palmer amaranth is most prevalent in the northern part of the state but has been confirmed in 39 counties across the state: LaPorte, Newton, Jasper, Pulaski, Cass, Benton, Porter, St. Joseph, Lake, Starke, Marshall, Fulton, Tippecanoe and White in the northwest; Adams, Kosciusko, Huntington, Elkhart, Wells and Noble in other northern areas; Henry and Shelby in east-central Indiana; Clay, Parke, Boone and Hendricks in the west; Lawrence, Jackson, Washington, Scott, Clark and Switzerland in the southeast; and Posey, Gibson, Pike, Dubois, Daviess, Spencer and Vanderburgh in the extreme southwest.

“Identification is the first, and often critical, step in an intensive management program farmers need to have in place if they are dealing with Palmer amaranth,” Legleiter said. “The next step is to apply a pre-emergent residual herbicide as close to planting as possible.”

Legleiter said he and Johnson plan to expand their test plot and set up cameras in the field again this year.

“We learned from our experience, and we hope to keep learning,” he said.

For more resources on Palmer amaranth biology, identification and management, visit the weed science home page.

University of Arkansas, Photo by Jeff Ingram

University of Arkansas, Photo by Jeff Ingram


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