Advanced Agrilytics

Part Two: Protecting the Crop Factory Through Grain Fill

As we discussed last week, this time of year the growing season can feel similar to reading a book, each chapter building more excitement and anticipation until the final plot line is delivered. We worked hard in the beginning to establish the crop and start what we call the Race to Canopy. The story continued as the crop factory was built in the mid- to late vegetative stages. Now, we can choose our own adventure during the critical grain fill period by considering the benefits of fungicide. This week, we’ll continue our discussion around fungicide use and the importance of timing.

While the best single fungicide application timing can be dependent on several factors, most often we can zero in on the VT (full tassel) to R2 (blister stage) window as most likely to provide maximum yield response.

What about making a second fungicide pass? While we historically would say that fungicide response rapidly drops off beyond the R3 stage (milk), in areas experiencing high levels of late season Tar Spot or Southern Rust pressure in 2021, we found second passes of fungicide as late as the R4 stage (dough) proved to be economically beneficial. If one of those diseases is prevalent at high levels in 2022, a second fungicide pass closer to the R3/R4 growth stage could be warranted.

Product selection is also a key consideration given the recent surge in Tar Spot and other more difficult to control diseases. There have been new product innovations introduced by several basic manufacturers of fungicide that provide new levels of disease control, residual activity, and plant health response. While these products do come at an additional cost, protecting bushels in today’s market is critical and makes these newer product entries well worth the investment, especially if disease pressure is expected to be high.

Alongside Mother Nature, we are the co-authors of our crops story, and as we round into the last chapter of grain fill, the pen is in our hands to tell the rest of the story.

We’ve discussed a few of the factors involved in making a fungicide decision, but this isn’t black and white, so we must be prepared for any twists in the plot that could be thrown our way. Our team of agronomists at Advanced Agrilytics is prepared to provide unique insights and an unbiased approach to fungicide, as well as other crop management decisions that can put some of that control back in your hands.

We welcome your questions about fungicide use or any of the challenges you’re experiencing this growing season. Contact us at or reach out to your local precision agronomist.

AJ Woodyard

Lead Agronomist – Illinois