Planting season has come to a close, and with the much needed precipitation, the green shoots of a new crop shall soon emerge. In amongst those tender new beginnings may be the “spawn of Satan”, a noxious weed so prolific it has set off one of the biggest warnings the agricultural world of North Dakota has seen in recent years. The weed is the dreaded Palmer Amaranth, and it’s spreading quickly across the Midwest.
By Melissa Anderson
This “game-changing” weed was declared a noxious weed in North Dakota in January of 2019, but NDSU Extension and weed control agents across the state were already talking about the weed that has caused major havoc already in parts of the United States. Cavalier County Extension Agent Anitha Chirumamilla and Cavalier County Weed Officer Leon Pederson have been working to inform area producers on the dangers this weed can pose to the favored row crops grown here.
Palmer Amaranth has earned the moniker of “spawn of Satan” or “demon plant” because it is so resilient and can come back so easily and quickly. The weed is considered a game changer because of the following characteristics that make it difficult to manage:
• Under optimum conditions Palmer can grow 1-3 inches per day.
• Prolific seed producer with up to 1 million seeds per plant.
• Can germinate throughout the growing season even after post-emergence herbicides have been applied or after crops have been harvested.
• Highly prone to herbicide resistance. It has been found resistant to 5 different modes of action including glyphosate.
“Palmer Amaranth’s prolonged emergence period, rapid growth rate, prolific seed production, and propensity to evolve herbicide resistance quickly makes this the most pernicious, noxious, and serious weed threat that North Dakota farmers have ever faced,” Rich Zollinger, retired NDSU Extension weed scientist, is quoted as saying.
Producers in North Dakota need to heed the warnings that other states are sharing after falling victim to the invasive member of the pigweed family.
Any weaknesses? It thrives very well in row crop situations. Small grains have a competitive advantage as they help in early row closure that suppresses late-season germination.
Palmer Amaranth competes aggressively with crops. It has a fast growth rate of 2-3 inches per day and commonly reaches heights of 6-8 feet, greatly inhibiting crop growth. Yield losses have been up to 91 percent in corn and 79 percent in soybean.
“It’s the only weed I’ve seen that can drive a farmer out of business,” said Bill Johnson, Purdue University Extension weed specialist.
The weed originated in the desert region of the southwest, specifically in New Mexico, Arizona, and northern Mexico, then spread to the Mississippi Delta. Palmer Amaranth is documented in 28 states including neighboring South Dakota, Iowa and Wisconsin. It has been documented in Douglas, Lyon, Todd and Yellow Medicine counties in Minnesota. In 2018, Palmer Amaranth was found in five North Dakota counties, the closest being Benson County.
Like many plants and weeds, seed is the means of spreading it with the female plants of the species being the most prolific seed producers. With both male and female plants, the genetic diversity has given the weed the ability to adapt and quickly spread herbicide resistant genes when selection pressure is applied. Purdue University notes that this most commonly occurs “when producers repeatedly apply single mode of action herbicides”. A study in Missouri documented more than 250,000 seeds produced per plant. Seed can be spread in water movement, by wildlife and via agricultural practices such as plowing, harvesting and spreading manure.
“We believe Palmer was introduced into the state through sunflower screenings, contaminated seed, custom combines, used combines purchased from other states and railroad cars. We know Palmer also can come through other ways, such as contaminated hay, birds, water and more,” Chirumamilla said.
As a member of the pigweed family, Palmer Amaranth can be hard to distinguish from some of its relatives. Three other common Amaranth species are redroot pigweed (Amaranthus Retroflexus), smooth pigweed (Amaranthus Hybridus), and common waterhemp (Amaranthus Rudis). The resemblance is especially strong during the seedling stages of growth which is when the plant is at its most vulnerable. Diligent monitoring and timely intervention are critical for the control of Palmer Amaranth, as cultivation and flaming are most effective on weeds not more than 1 inch tall.
The key identification characteristics are:
1. Smooth stems with no hairs.
2. Long petiole- the petiole of lower leaves are longer than the length of leaf blade.
3. Dioecious Plants- male and female plants are separate. Female plants are wide and robust, male plants are thin.
4. Spiny bracts on female plants.
5. Unbranched long seed heads- male are smooth, female are prickly.
Depending on the source where the seed has come from, it can grow anywhere. Palmer Amaranth can germinate in many places including cropland, pastures, gravel lots and marginal areas. Cavalier County Weed Officer Leon Pederson notes that it is a very prolific noxious weed and will take over a field in two years.
“Currently, North Dakota is in a position where we can minimize the impact of this weed because it is not widespread like it is in other states,” Chirumamilla said. “However, to stay ahead of the weed, we need to control what has been found and be very vigilant to not bring more seeds into the state. Farmers, agronomists, and companies need to ask questions, conduct inspections and do whatever is necessary to avoid bringing in contaminated seed, feed or equipment that will spread Palmer Amaranth, raise productions costs and reduce yields.”
For more information on Palmer Amaranth, including how to identify it, visit the NDSU website www.ag.ndsu.edu/palmeramaranth.
NDSU Exentsion and the North Dakota Department of Ag are asking that residents and producers contact Extension Agent Anitha Chirumamilla at 256-2560 or County Weed Officer Leon Pederson immediately to verify a suspected plant.
Pederson stated emphatically to please be on the look out for these plants and contact your county weed or Extension officer immediately. Do not remove the weed before one of them identify it. After identification is complete, they will help you come up with a control plan.