Pesky Palmer pigweed proliferates
The seedlings are susceptible to herbicides, but they must be sprayed early. If spayed late, the weeds escape death.
"It's a serious weed threat and takes serious management," Bradley said. "But it can be controlled with extra work and expense."
Controlling early before seed-set pays off. First priority is to prevent seed production and building a seed bank.
Narrower soybean row-width helps control pigweeds. Drilled beans have fewer pigweeds as shade covers the ground earlier. More weeds are found in 30-inch rows.
Increasing seed planting rates boosts odds in favor of the soybean over pigweed seedlings.
Herbicides give control, but lax management won't work with the rapidly growing Palmer pigweeds. The seedlings quickly accumulate growth, requiring more herbicide. Palmer produces up to 65 percent more dry matter after two weeks than other weed species.
With more foliage, it's hard to get enough ingredient on the plants.
More than one herbicide mode of action is a must. For that, Bradley recommends "overlapping residuals." That leaves less time for the continuation germination of the Palmer pigweed.
Using just one mode leads to resistance. "I visualize how Palmer pigweeds became resistant to glyphosate," Bradley said. "Someone used only that herbicide season after season."
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