Critical Period Of Weed Control

Keep the crop clean through the first weeks to maintain peanut yield.

palmer pigweed

Palmer pigweed

Weed management is truly a year-round process. It may begin in planning before the crop is planted, but it really never ends.

The harvesting of the crop may only signal the start of field record keeping, where weed problems and successes are documented. Since this is the start of planning for the next season, it’s easy to see how this circle doesn’t end. Even so, there is a critical time for weed management.

The critical period of weed control — says Jason Bond, Mississippi State University research and Extension weed specialist — that’s the time that you’ve got to control weeds to keep from losing yield is right after that crop comes out of the ground.

Clean Field=Maximum Yield

“Those first few days or weeks after the crop emerges is when you have got to keep the crop clean to maintain yield,” Bond says. “It varies by crop and other variables, but the point is the critical time to have a clean field — for all crops — is the first few weeks after the crop comes out of the ground.”

Bond says for about the last 10 to 12 years, Palmer amaranth has driven the train.

“If you’ve got Palmer and can’t control it, then it doesn’t matter about the morningglories or prickly sida. It matters whether you can control Palmer amaranth or not.”

Bond says the best time to get weeds is before they germinate. “Target the seedbank with residual herbicides, which are the cornerstone of our recommendations,” he says. “You can’t afford to have Palmer amaranth ahead of your crop.”

But eventually, residual herbicides will wear out and weeds will start popping up.

Control The Competition

“Early season weed control is essential for reducing competition for water, nutrients and light between the peanut plant and weeds,” says Emi Kimura, Texas A&M University Extension peanut specialist. “In addition, the soil seed bank will be reduced by controlling weeds before they make seed with timely applications of postemergence herbicides.”

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Early post applications are made at 10 to 20 days after planting and postemergence applications at 30 to 45 days. In an article,

“Early Season Weed Control Options for Peanut,” Kimura, along with TAMU’s Josh McGinty, Extension agronomist, James Grichar, Senior Research Scientist at Yoakum, and Pete Dotray, Extension weed specialist, reminds producers to consider the following factors.

Apply In Good Soil Moisture

Weeds must be actively growing to absorb and translocate the herbicide for maximum efficacy. When herbicides are applied to weeds growing under stressed conditions, such as drought, high temperatures, disease or insect damage, reduced efficacy is often observed.

Consider Coverage And Spray Volume

Always use enough spray volume to achieve good coverage for improved weed control. Often, weed control failures after the application of POST herbicides are due to low spray volumes and insufficient spray coverage.

Use Appropriate Adjuvants

Adjuvants such as non-ionic surfactants and crop oil concentrates reduce the surface tension of the spray solution and help dissolve or soften cuticular waxes on the leaf, improving uptake of the herbicide. Additionally, many product labels recommend the addition of ammonium sulfate or urea ammonium nitrate to improve efficacy. Always check the product label to see what adjuvants to include.