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.
In Mississippi, 90-plus percent of rice is grown in rotation with soybeans.
“We have some real opportunities in rice to manage pigweeds. My favorite herbicide combination is propanil plus Grandstand. But you also have the flood — and you can’t beat a flood for managing Palmer pigweed” as it is native to an arid climate.
However, Bond cautioned about one big drawback for managing pigweed populations in rice: preventing seed production on levees. Pigweeds may not survive a flood but they can thrive on a levee throughout the summer.
How can Palmer amaranth control work with a general rice weed control program targeting grass and broadleaf weeds?
“SuperWham plus Grandstand applied at a mid-post timing (three- to four-leaf rice) provided 98 percent control.”
Another option is Broadhead, a pre-mix of quinclorac plus Aim. “Broadhead, in the limited experience I’ve had with it, has done a very good job on very small pigweeds. It has done a poor job on larger pigweeds because one of its components — the one doing the major effort to control pigweeds — is Aim. Aim is a contact herbicide that needs excellent coverage and, obviously, works better on smaller weeds.”
Because of the ALS-resistant pigweeds in fields around Stoneville, “we only get around 65 percent control with Aim plus Permit. But if we can injure those plants and then get water on them within 10 days or two weeks, it seems that even though they don’t die from the herbicide application they’ll melt down and die quicker if they were at least injured.”
Bonds said it’s too common for growers to “wait for the pre-flood timing to treat most broadleaf weeds in rice. At that point, the weeds are just too big. Even though the flood will control the pigweed you have endured four or five weeks of competition. If the pigweed population is thick enough, you can incur some real yield losses before the field is flooded.”