Foliar Soybean Fungicides

Thinking of using a fungicide on soybeans this season? When will you apply it and is it likely to work this year?

I have had several local producers ask if they should “waste their money on soybean fungicide this year?” My reply is that first off you’re not wasting your money, you are investing in your crop, and with foliar fungicides you are protecting your yield potential. With foliar fungicides it’s all about reducing the stress the soybean plant has at key times during its development.

When is the best time to apply foliar fungicides? The sweet spot for an application of foliar fungicide is at the R3 stage (pod set). Why R3? Temperature or moisture stress at R3 can affect yield through total pod number, bean number per pod or seed size. Approximately 60% – 75% of most flowers typically abort, and any stress that increases abortion will greatly influence yield. An application of a good foliar fungicide at R3 should get you at least 20 days of residual control. Any stress during the time from R4 to R6 can cause more yield reduction than at any other time. Late pod formation at R4.5 to early seed fill at R5.5 is when it is most critical to limit stress on soybeans. But to protect the plants at R4 to R5, you have to spray a fungicide at R3 to prevent an infection from occurring.

Data from 2014 studies conducted by Syngenta showed a 5.2-bushel advantage per acre when Quadris Top® SB was applied vs untreated fields.

Applying foliar fungicides with a post-herbicide application to simply save a trip across the field is not recommended because the timing is off. Application of an herbicide is based on weed height and pressure, not on the growth stage of the soybean crop. Timing is critical for a foliar fungicide application. Producers will be disappointed with the results if application timing is not correct and they apply too early.

It is also suggested that you add an insecticide to the fungicide application. It’s a minimal cost addition and could show huge returns. Studies have shown that when you apply foliar fungicides, in many cases insect pressures will increase due to the healthier soybean field.

With all the stress this current crop has been under and the stress-mitigating capabilities of foliar fungicides, I believe we will see a huge benefit from R3 applications this year.

I would be glad to hear your comments or address your concerns. Please contact me at wade.meteer@syngenta.com.