Many preemergence and postemergence corn herbicide combination products are formulated with a safener, such as isoxadifen or cyprosulfamide. These additives increase the activity of enzymes within the corn plant that detoxifies the herbicide for improved crop safety.
Without safeners, some corn herbicide combinations would not be available to help farmers save valuable yield during the most critical period when weeds compete with the crop.
“For example, our Group 15 preemergence herbicides could definitely lead to corn injury without safeners," points out Erin Burns, Michigan State University Extension weed scientist.
"By helping corn withstand the herbicides, safeners opened the door to better residual chemistries to reduce weed competition in those critical first three to four weeks of corn growth."
Safeners also have another benefit. “The most interesting aspect of these safeners is that they only protect monocot crops like corn, rice, sorghum and wheat, but not weeds,” she says.
In years like 2022 with high input costs and variable weather across many corn-growing regions, Burns recommends making sure your choice of herbicides won't unintentionally injure your corn crop. “Safeners are just a good added layer of insurance to protect yield, especially when dealing with cool and wet springs.”
Growers who try to pinch costs and don't apply a preemergence herbicide can run into issues, continues Burns, “if the weather is cool and wet by the time you apply postemergence products, that layer of yield protection insurance from safeners might not be there. Check with your weed control advisor and product labels to determine crop safety as some postemergence products like Realm® Q or Resolve® Q herbicides contain safeners.”
Burns also cautions farmers against reducing label rates of preemergence herbicides to cut costs. The risk is more significant in diminishing weed control effectiveness and reducing the amount of safener applied. “I haven’t heard of any research on the potential impact of reduced safener levels, but I would guess the potential exists for added crop injury,” she says.
It's always important to consult herbicide labels for precautions that may impact crop safety and weed control efficacy. The label will describe soil characteristics like texture, organic matter and pH that might affect corn injury potential. Adverse weather, like extended periods of cool or cold, and wet conditions during crop germination can also cause temporary injury symptoms.
The herbicide label may also suggest possible sensitivity to corn hybrid genetics, so it’s wise to contact your seed provider for further details.
Finally, Burns studied herbicide-resistant weeds to determine if safeners played a role in reduced weed control. “They did not boost the enzymes in resistant weeds, so we found no change in the control efficacy against weeds,” she says.
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Realm® Q and Resolve® Q are not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions.
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