FMC launched a series of “explainers” in last month’s Byline covering basic concepts in pest or weed control. Last month’s topic was “How a herbicide works.” This month’s explainer is “The biology of Palmer pigweed.”
The Biology of Palmer Pigweed
There are many hard-to-control weeds, especially in soybeans, but one of the worst is Palmer pigweed, a weed indigenous to the South that is moving north with lightning speed.
“Palmer pigweed is hard to control because of its biology,” explains Brent Neuberger, weed scientist and senior technical sales manager with FMC. “It’s a broadleaf weed with multiple growing points. Post herbicides can get to the top growing points, but the bottom ones are harder to reach especially as they become larger.”
He says the same is true of waterhemp, which comes from the same weed family.
Palmer amaranth can be identified by its wide leaf with wavy edges and long petiole, the stalk that attaches the leaf blade to the stem. It has no hairs except in the leaf notch, and a portion of the population may have a watermark. Photo from: Purdue Weed Science.
“Palmer pigweed is like waterhemp on steroids,” Neuberger says referencing its growth rate. “It can go from 1 inch to 4 inches in a couple of days, and it germinates throughout the season; first in the spring and then multiple flushes throughout the summer.”
As a result, you might end up having to spray multiple times to stay ahead of it, which leads to an even bigger problem.
When you excessively spray a single class of herbicides, weeds start to develop resistance. It’s a problem plaguing the treatment of Palmer pigweed and waterhemp.
“Both Palmer pigweed and waterhemp are prolific seed producers,” Neuberger says. “Just one resistant weed that survives treatment can produce 200,000 – 500,000 seeds. What may have started out as a small patch of weeds can turn into a big mess in a couple of years.”
So, how do you kill Palmer pigweed and other tough weed species? The best first step is to keep them from emerging in the first place by putting down preemergent residual herbicides, such as Authority® brand herbicides from FMC. Preemergent herbicides prevent the establishment of a high weed population that can be difficult to control with post herbicides. It’s about managing the weed seed bank to keep numbers low, as explained in last month’s column on “How a herbicide works.”
“You need to get it early,” Neuberger says. “A weed that doesn’t emerge will never develop resistance to a postemergent herbicide.
For more information on how to control Palmer pigweed or any other weed species, go to FMCcrop.com or contact Jodie Wehrspann at [email protected], who can arrange an interview.
Brent Neuberger is a weed scientist and senior technical sales manager with FMC.
Always read and follow label directions. Authority brand herbicides are not registered for sale or use in California. FMC and Authority are trademarks of FMC Corporation or an affiliate. ©2017 FMC Corporation. All rights reserved. 17-FMC-1068 10/17