In 2020, corn foliar fungicide trials were conducted at six locations in Iowa to help farmers determine if a foliar fungicide was necessary. The objectives were to assess the effect of application timing on disease, evaluate the yield response of hybrid corn to foliar applications and discern differences, if any, between products.

The six locations were:

Six products at various application timings were evaluated (Table 1). Fungicides were applied at growth stage V12 and/or R1 based on the company's suggestions. No surfactant was included in applications made at V12.

Disease control

Below are results on the effect of product and timing on foliar disease:

Yield outcome

Management recommendations

All fungicides in these trials were effective against gray leaf spot. For a list of fungicides effective against GLS and all diseases on corn, check out Fungicide efficacy for corn diseases at the Crop Protection Network. This publication is updated annually by corn pathologists across the U.S. and Canada.

Applications at V12 reduced GLS severity more than applications made at R1. These data are similar to what we reported in 2017,where V12 applications also reduced GLS more than applications at R1. Remember GLS always starts in the lower canopy. With applications at V12, fungicides are more likely to reach the lower canopy and protect the lower leaves.

More results include:

To limit resistance developing to fungicide chemistries, reserve fungicide applications for fields that are more likely to have disease, such as those planted to susceptible hybrids, low-lying fields where morning fogs often occur, or fields with a history of disease.

Follow local Extension pathologists and agronomists on social media to stay informed on diseases prevalent in your area, the risk of disease, and the need for a fungicide application.

Robertson is an associate professor of plant pathology and microbiology at Iowa State University.

Source: Integrated Crop Management News and Iowa State University Extension, which are responsible for the information provided and is wholly owned by the source. Informa Business Media and its subsidiaries aren't responsible for any of the content contained in this information asset.