What is in this article?:
- Crop rotation to manage glyphosate-resistant pigweeds.
- Also in the mix: rotation considerations for rice and levees.
- Report from the Pigposium.
The biggest problem spot with rice and pigweeds is the levees.
“If you leave a pigweed on a levee and it makes seed, it’s just like allowing Palmer pigweed to go to seed after corn harvest. (Almost) every effort you’ve made to manage that population will go out the window. Because once you’ve swiped that levee down (in preparation) for next year’s soybeans, you’ll do a good job of evenly spreading those pigweed seeds from the levee across the field.”
Data from work done by Jason Norsworthy, weed scientist with the University of Arkansas Division of Agriculture, showed that “no herbicide or combination does an excellent job of controlling pigweed on levees. Plants are probably 18, 24, or even 30 inches tall at time of application because we normally spray levees later in the season.
“Propanil and 2,4-D was the best treatment they had in (the test). In my opinion, the major goal of pigweed control on levees is preventing seed production. That’s particularly true if you haven’t seeded the levees to supplement your per-acre grain yield. Do what you must to keep it from making seed.”
There are other benefits of crop rotation including breaking disease, insect and nematode cycles and improving soil conditions. But from a weed control standpoint, “if the appropriate herbicides are chosen and applied correctly, then rotation can be a big tool we can use to manage pigweed populations.
“Again, rotate herbicide chemistries and exploit cultural tactics available in (each) rotational crop. If you’re going to grow a rotational crop with an eye towards managing resistant pigweeds, then you must target 100 percent control.”