Foliar Fungicide Application to Corn

July 27, 2009 at 8:00 am

Late July through early August used to be a time when things settled down on most farms. The last of the herbicides had been sprayed on soybeans, and wheat has been baled and stored.  During the past couple of years, however, there has been a push to apply foliar fungicides to corn during the critical corn reproductive stage.  Questions remain as to the efficacy of applying fungicides to corn this time of year, and whether or not this practice is warranted.

In this video clip shot July 23, 2009, I am spraying my corn fungicide trial with Stratego @ 10 oz/acre + NIS @ 0.125% v/v. Volume was 15 GPA at 40 PSI with XR11004 on very early VT corn. I noted less than 1% leaf area had rust, no other diseases were present. Thanks to Brent Neate for application and use of the Walker 44.

I am involved with three studies over the past three years looking at this very issue.  I have data to share for 2007 and 2008, and will be releasing the 2009 data following harvest this fall.  Below, I will summarize the results from 2007 and 2008 studies.

The studies from 2007 and 2008 are similar in design.  In both years the study was set up as three treatments with four replications of each treatment in a randomized complete block design. Plot size was 45 feet wide by 1090 feet long. The treatments tested were: 1) Untreated check, 2) Headline at 6.0 ounces per acre + nonionic surfactant (NIS) at 0.25% v/v, and 3) Stratego at 10.0 ounces per acre + nonionic surfactant (NIS) at 0.125% v/v.  Fungicide applications were made with a high clearance ground sprayer in 15 gallons per acre spray volume at 50 psi using TeeJet XR11004 flat fan nozzles.

Due to differences in growing seasons between 2007 and 2008, the application date was different.  In 2007, both the Headline and Stratego foliar fungicide treatments were applied on July 18 with corn at growth stages VT-tassel emergence to R1- silking.  In 2008, both the Headline and Stratego foliar fungicide treatments were applied on August 8 with corn at growth stage R2-blister.

Results of the studies are similar. Data from the trials indicates there were no statistically significant differences between the treatments for corn yield.  Visual inspections during the growing season did not show any significant disease pressures in any of the plots, but the fungicide treated plots did have greener plants later in the season.  Here are the actual yield numbers for 2007: untreated check = 184.6 bushels/acre, Headline = 183.4 bushels/acre, and Stratego = 188.0 bushels/acre.  Here are the actual yield numbers for 2008: untreated check = 118.2 bushels/acre, Headline = 123.9 bushels/acre, and Stratego = 125.5 bushels/acre.  Variability between the yield means is most likely being caused by other outside influences and cannot be attributed to the fungicide treatments based on the statistical analysis.

The complete studies (which include data on hybrid, planting date, fertility, etc.) are available online at: and  For more information on corn diseases and fungicides recommendations for corn, please stay informed with the weekly updates from the OSU Extension Agronomic Crops Team CORN Newsletter at


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