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Focus on Fungicides

April 30, 2011
By: Rhonda Brooks, Farm Journal Seeds & Production Editor

Farm Journal Test Plots Examine Application Timing

The benefits of using fungicide in corn aren’t always clear-cut and easy to measure. Field research conducted in 2010 in the Farm Journal Test Plots by Ken Ferrie and Missy Bauer, Farm Journal Field Agronomists, set out to get a handle on application timing.

One of the questions the agronomists wanted to answer was how an early season fungicide treatment in corn at the V5 growth stage would compare to an application at the R1 stage, which is the traditional timing for fungicide applications.

A second question was whether there was any benefit to applying fungicides at both times, compared with making one application at one or the other timing.

Bauer, who is based in southern Michigan, explains that yield potential in corn begins at around the V5 growth stage, so some manufacturers recommend applying a fungicide at that point to provide what the chemical industry calls a plant health response. Fungicide applications made at the R1 corn growth stage are used to shut down disease pressure.

For the studies, she evaluated the performance of Syngenta Quadris and Quilt Xcel fungicides and BASF Headline and Headline AMP fungicides.

All products were applied at labeled rates in southern Michigan irrigated fields owned by North Concord Farms in two different rotational scenarios: corn on corn and corn after soybeans. The test plots ranged in size from 25 acres to 50 acres and each contained one 105-day hybrid and one 106-day hybrid, based on comparative relative maturities. Both hybrids offered low to moderate susceptibility, depending on the disease specified. Each trial was replicated three times. No comparative studies were conducted between the products.

Yearly rainfall levels were average for the 2010 season, but disease pressure in the fields, specifically northern corn leaf blight, was at the heaviest level Bauer has ever experienced in the area.

When Bauer evaluates fungicide treatments, aside from hybrid response, she typically finds that the best response is in irrigated fields that are planted into corn-on-corn rotations.

Ferrie agrees with Bauer, noting that his 2010 fungicide studies also were based on the treatment timing of R1 and V5 but were made only in non-irrigated fields with corn on corn and corn after soybeans.

"High disease pressure from old corn residue, extended periods of leaf wetness and adequate soil moisture allow disease to proliferate," Bauer says. "Agronomically, that’s a tough scenario that should help fungicides have the most positive response."

In ranking the responses to fungicides in Bauer’s three other agronomic scenarios, corn on corn in nonirrigated fields is second best; irrigated corn grown after soybeans is third; and the fourth best scenario is corn grown after soybeans.

"It’s important to not only consider the hybrid disease ratings but also the cultural practices and environment," she explains. "You must respect the disease triangle."

Key take-aways.

Fungicide treatments that were made at V5 were economically advantageous in Bauer’s plots 75% of the time and 100% of the time in applications made at the R1 timing (see charts below).

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FEATURED IN: Farm Journal - Late Spring 2011
RELATED TOPICS: Test Plots, Inputs, Production

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