A pair of time-lapse videos showing rapid growth of Palmer amaranth in research fields last summer might be enough to make some growers reconsider the weed's threat in 2015.
Purdue University weed scientists developed the videos, which also show the effect of pre-emergent herbicides used to control Palmer amaranth.
"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."
First step: Palmer amaranth identification
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.
"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.
In the coffee shop, it is known as Palmer pigweed. In university circles, it is referred to as Palmer amaranth. Whatever you want to call it, this weed is the No. 1 weed to watch. Stay on top of your control plan with our new free report, Palmer Amaranth: Understanding the Profit Siphon in your Field.