Paul says there is a likelihood of problems in Ohio with the excessive rain, and if that has been an issue for your farm, he says look for lesions on the leaves, “If your hybrid is susceptible, a fungicide is usually recommended when lesions are observed on the ear leaf and the leaves below the ear on 50 percent of the plants - 50 plants with lesions out of 100 plants examined across the entire field.”
At Purdue, Plant Pathologist Kiersten Wise agrees with Robertson at Iowa State and says, “Many fields across Indiana are currently at a younger growth stage than normal due to delayed planting, and therefore may be at greater risk for yield loss due to disease development. “
And she says don’t delay in scouting for fungal problems, “Research in Indiana indicates that fungicides are most effective at preventing yield loss due to disease when applied at the tasseling to early silking (VT-R1) growth stage. Scouting fields around V14, or just prior to tassel emergence, can help determine the level of disease pressure in a field.”
Wise is most concerned about gray leaf spot, and says if your corn is susceptible, take precautions now:
- Consider a fungicide application if the hybrid is rated as susceptible or moderately susceptible AND 50 percent of the plants in a field have disease lesions present on the third leaf below the ear leaf or higher prior to tasseling. (watch her video).
- Consider a fungicide application if the hybrid is rated as moderately resistant AND 50 percent of the plants in a field have disease lesions present on the third leaf below the ear leaf or higher prior to tasseling AND additional factors or conditions that favor disease development are present (residue present, favorable weather conditions)
If northern corn leaf blight is your issue, Wise says there are no treatment thresholds, but apply the same recommendations for gray leaf spot. And she says use the fungicide efficacy table for treatment recommendations.
Another issue that may have escaped you is any damage to corn from wind or hail. Those can open wounds in corn, and soybeans as well, and allow fungal spores to begin multiplying. Iowa State University plant pathologists say they do not require such wounds, but based on 2012 research, there were some conclusions that were drawn:
- Non injured plots yielded more than those injured by simulated hail.
- For soybeans there was more damage from hail at the R1 stage than at the R4 stage.
- For corn hail at R2 was more serious than hail at the VT state.
- Fungicides applied 7 days after a hail event recorded better yields than fungicides applied 2 days after a hail event.
- Fungicide application on corn usually resulted in better yields over corn that did not have a fungicide applied.
While university-based researchers may not be ready yet to endorse crop fungicide application “as a precaution,” this year does get their nod due to the likelihood of seeing fungal issues develop from the environmental issues impacting crops this year. Cool and wet problems can create leaf blights and scouting for them should be a priority.
Source: FarmGate blog