Farm Horizons, June 2014

Value of foliar fungicides for corn production

By Dave Schwartz
Certified crop advisor,Gold Country Seed

Corn fields normally go through a strong growth spurt in late June and early July. Warm temperatures, typically associated with the Fourth of July, trigger this response. Green snap is always a concern during this period of rapid growth.

Corn goes from knee-high to tasseling in just a few days, so if corn growers plan to use a foliar fungicide, pollination is the time period foliar fungicides need to be applied.

Foliar fungicides are effective at controlling fungal diseases, such as anthracnose, gray leaf spot, eyespot, northern leaf blight, rust, etc.

From what I know, growers in states to the south and east of us usually see more yield response from foliar fungicides, because they have more disease pressure. These states have more rainfall and humidity; necessary ingredients for fungi to thrive.

States to the northwest that are normally dryer see less disease pressure in their corn. So, is it economical for corn growers in Wright County to apply fungicides?

The answer, as is often the case is, maybe.

If growers do test strips on their farms, they most likely will find one of three things – no yield response, positive yield response, and, occasionally, a negative yield response.

Where growers are most likely to get an economic return is in fields that have been continuously corn, because these fields have more disease pressure. Fields with very high yield environments are also good candidates, such as fields under irrigation. Corn hybrids have different disease tolerance, so this is an important factor, too. Growers may see more disease pressure if they are in a reduced tillage system, where more crop residue is left on the surface.

One important thing to remember is that fungicides are not effective on bacterial diseases, such as Goss’s Wilt. Fungicides control fungal diseases, but have little effect on bacterial diseases or virus. Crop rotation and hybrid selection are the best control methods to manage Goss’s Wilt.

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