If you live in the Southwest United States and have a farm, you are probably familiar with Palmer amaranth (Amaranthus palmerii), one of the most aggressive and competitively successful pigweed species in the world.
In today’s New York Times, H. Claire Brown’s article, Attack of the Superweeds, offers insight into the devastating potential of this plant and the undeniable resilience of nature.
“Superweeds — that is, weeds that have evolved characteristics that make them more difficult to control as a result of repeatedly using the same management tactic — are rapidly overtaking American commodity farms, and Palmer amaranth is their king.”
Even after applications of incredibly dangerous herbicides such as dicamba or the more deadly paraquat, which can kill humans, this weed will re-establish and grow again. Pulling them out of the ground is not necessarily a successful eradication method either. Seeds from the previous year’s plants may be dormant in the ground and will emerge.
Palmer amaranth, unlike most commodity crops, is genetically diverse and may produce random mutations in its offspring, which is key to its success. Consequently, genetically resistant plants survive. Consider that a single plant generates approximately 250,000 seeds and you’ll begin to understand how this plant can quickly dominate a landscape.
Additionally, according to the Minnesota Department of Agriculture, this weed will grow 2 to 3 inches per day to a height of 6 to 8 feet. As a result, farmers have reported yield losses of up to a staggering 91% of their planted corn and 79% of their soybeans.
Farmers and scientists now believe that most herbicides will be useless against this and other superweeds in approximately 10 years. If current farming practices continue, superweeds will ultimately overrun many domestic crops.
In February 2021, a related paper was published in the journal, Weed Research which focused on understanding this plant’s phenology cycle. The research describes the air and soil warmth patterns to determine when the plant would first emerge, then begin to flower, and begin to produce seed, as well as other stages within its life. Clues to the weed’s vulnerabilities may be identified, reducing the need for increasingly toxic herbicides.
The NYT article mentions that the farmer portrayed in the story is attempting to plant the crop rows closer together to block out the sun from the palmer amaranth seedlings. I don’t know if this will work, but it is an interesting idea that acknowledges how the weeds function.
Perhaps more new farming ideas could be tested as well. Maybe it is time to move beyond monoculture. We need to at least try.
To read the excellent article, Attack of the Superweeds by H. Claire Brown here is the link: https://www.nytimes.com/2021/08/18/magazine/superweeds-monsanto.html
If you can’t get behind the paywall, check with your local library to see if they can help you access a copy in print or digitally.
Minnesota Agriculture report on Palmer amaranth — https://www.mda.state.mn.us/plants/pestmanagement/weedcontrol/noxiouslist/palmeramaranthAn
An abstract of the phenology model of this weed — https://onlinelibrary.wiley.com/doi/10.1111/wre.12470