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Northern Illinois Agriculture

University of Illinois Extension
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Herbicide injury starting to show in northern Illinois corn fields


Stephanie Porter sends a weekly summary of diseases and plant injuries diagnosed from samples submitted to the University of Illinois plant clinic. Visit the plant clinic site to learn all that they have to offer

http://web.extension.illinois.edu/plantclinic/

In this week's report several corn seedling samples had been diagnosed as chemical/herbicide injury. I noticed several examples of herbicide injury at the NIARC as well. Dr. Aaron Hager recently shared that the increased observation and inquiries from herbicide injury appears to be statewide.

From Aaron's article; "Many postemergence corn herbicides routinely cause some corn injury," said Hager. "Some growers, however, have the impression that this year there is a bit more injury than usual.

Hager said that several factors can affect the sensitivity of corn to injury from postemergence herbicides, including:

• Hybrid: Hybrids have varying sensitivity to herbicides labeled for use in corn. For example, some corn hybrids are sensitive to specific ALS-inhibiting herbicides and tend to exhibit considerable injury following herbicide application. Many corn herbicide labels (especially labels of postemergence corn herbicides) carry warnings that certain corn hybrids could be sensitive to the active ingredient.

• Environmental conditions: High air temperatures and relative humidity levels favor rapid absorption of foliar-applied herbicides, but some environmental conditions can induce crop stress, slowing the rate at which the crops metabolize the herbicide and leading to increased herbicide-related injury. For example, cool air temperatures and wet soil can induce crop stress.

• Spray additives: Crop response may be enhanced when spray additives are applied with a postemergence herbicide or tankmix combination because of the increased rate of herbicide absorption into the plant. Be sure to read all label suggestions and precautions related to spray additives that should be either included or avoided when applying herbicides postemergence.

• Contamination: Herbicide residues from prior applications may be applied inadvertently with the postemergence corn herbicide. These residues, either alone or in combination with the postemergence corn herbicide, may enhance the amount of corn injury. The type of contaminant and the dose at which it is applied affect the severity of the corn response to spray contamination."

Dr. Hager's article can be read in its entirety here

http://web.extension.illinois.edu/niarc/news/news27443.html


What can producers do when they notice herbicide injury to the crop? Inmost instances the only option is simply to wait and see if the corn successfully metabolizes the herbicide and re-starts its growth. With our recent favorable weather this should happen in most situations but we should keep an eye on those areas of the field and make a mental note to prevent it from recurring in future crops. Careful selection and matching of herbicides and hybrids coupled with pesticide placement should remedy most issues.


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