What is the Correct Time to Apply Foliar Fungicides to Soybeans?

Spraying soybeans with a foliar fungicide has not been common practice in Ontario. Over the last 10 years there has been increased interest in applying foliar fungicides to soybeans. Many trials have been conducted in Ontario to assess the yield and seed quality benefits. Averaged across 5 years of trials the average response has been 2.3 bu/ac. Seed size and quality can be improved, especially when there is significant disease pressure. In 2012 Dr. David Hooker (University of Guelph, Ridgetown) conducted trials to evaluate the correct timing for maximum economic return. The trial results were surprising in that soybeans responded more when sprayed relatively early. An application at the R2.5 growth stage (full flower) provided more yield than at later growth stages. Refer to Figure 1.

Timing of Foliar Fungicide

Although the economic return on fields with no disease is questionable, it does appear that earlier application timing may be necessary to maximize yield response. More trials are being conducted in 2014 to assess the best timing, including in-furrow applications. Stay tuned for the results.

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