Understanding the Importance of Fungicides
Soybeans are often overlooked, specifically during the plant’s reproductive stages. This is unfortunate because a soybean plant doesn’t reach 50% dry matter accumulation until R4, or full pod. At this stage, seeds have just become visible within the pod, so we have a long way to go until maturity.
Unfortunately, this is also a time of year where soybean diseases can be found within the soybean canopy. Usually, if we are expecting good soybean yield due to moderate rain and favorable temperatures, those conditions are also favorable to soybean diseases such as Frogeye Leaf Spot. Frogeye Leaf spot is of significance because it is becoming resistant to strobilurin fungicides, which are used in many common fungicide premixes across the Midwest. If you live in an area where resistance is a concern, Viathon is a fungicide that doesn’t rely on a strobilurin chemistry for its residual control. But, if strobilurin resistance isn’t an issue for you, Avaris 2XS is a great choice that has shown similar benefits when compared to the SDHI carboximide fungicides.
Regardless of the product choice, good coverage is a must because of the dense canopy structure in soybeans. To achieve the best coverage, we recommend high gallons and a quality adjuvant like Cide Winder®. Unless we are talking about managing white mold, when it comes to fungicide timing, the data consistently shows that spraying at the R3 growth stage (3/16” pod in one of four uppermost nodes) gives the greatest return on investment. There is over 20 years of research proving that the R3 application provides the largest yield bump – generally between 5 - 7 Bu/A, if white mold is not present. If that is not possible, we recommend spraying a little later, rather than a little earlier.
Most fungicide passes have an insecticide like Sultrus or Tempest added to it. Additionally, many tissue tests have shown deficiencies in sulfur, boron, manganese and zinc as soybeans start to flower. Putting a foliar fertilizer in the tank can help correct these deficiencies and increase yield in the fungicide pass.
Talk to your local Helena representative for more information about the recommendations in this article and to build out your plan for maximizing your soybean potential this season!
- Written By: Matt Boyer & Bill Verbeten, AGRIntelligence Agronomist