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Fungicide Application; Silage Harvest; and Impact of the Hazy Skies and Nighttime Temps

BY Dairyland Seed Agronomy Team

Fungicide applications on corn and soybeans are being made across our region. A common question asked as planes fly and sprayers roll is, “when do we stop application of fungicides?”.

Applications of foliar products offer some amount of return on the investment, and application timing is the key to the amount of return.

  • The application window of fungicide on corn is VT (tassel) to R2 (blister or brown silk).
  • The soybean fungicide application window is R3 which is beginning pod. This stage is identified by a 3/16-inch-long pod at one of the four uppermost nodes.

Application at these growth stages have shown the greatest return on investment; thus, our recommendation for cutting off fungicide applications would be R2 (blister or brown silk) in corn and after R3 in soybeans.

Insecticides are a common tank mix partner when applying fungicides, and as the year progresses, it is important to review the PHI or Pre-Harvest Interval of these products to be sure that that harvest will not occur before the PHI expires. Some products can have 3+ week PHI, for example Lorsban® Advanced has a PHI of 21 days for corn and 28 days for soybeans.

If you have questions on fungicide or insecticide application windows or PHI, contact your Dairyland Seed DSM or Regional Agronomist for more information.


 A few weeks ago, we provided a primer to corn silage harvest in our weekly newsletter. Dairyland Seed’s on-farm strip trial data demonstrates the importance of harvest timing with regards to whole plant moisture.  This could prove especially important in a year like 2021 where different geographies are receiving different kinds of moisture stress and silage maturity. More on that in future issues of the newsletter.

Below are data from 2019 and 2020 on-farm silage trials with BMR and HIDF products broken out separately. As a function of harvest moisture, we present milk/acre and milk/ton as a percentage of the overall (BMR and HIDF) average. This allows values to be compared across charts. A quadradic trendline was the best fit for each dataset, and we only included plots over 50 percent moisture.

The first thing that jumps out from the data is the overall variability of the data set. Since on-farm trials generally lack replication, this is quite normal. The main takeaway is that, while moisture is important, forage yield and quality is driven by a complex number of factors that can be very site specific. Watch for more information diving into that topic in the future.

The tradeoff between BMR and HIDF with regards to milk/acre and milk/ton is apparent when we look at the maximum of the trendlines. HIDF offers a large advantage in milk/acre, while BMR edges out HIDF with milk/ton. While we consider that a percentage difference in milk/ton means much more than a percentage difference in milk per acre, we tend to favor the milk/acre advantage of HIDF for most farms. The most important advantage that BMR holds is the slightly flatter milk/ton curve. This means that BMR has a wider harvest window if pure forage quality is your priority.

Our previous newsletter pointed to 64-68 percent as the ideal harvest moistures and our data backs that up nicely, regardless of silage type. Be sure to get started when moistures are near 70-72 percent so that the bulk of your forage is put into storage while in the sweet spot. 


The recent wildfires in the western United States and Canada have caused the sky to be quite hazy. The hazy sky tends to be more noticeable at dawn or dusk with the red or orange hues around the sun which contain dust, but mostly smoke particulates from the wildfires. The dust and smoke particulates block solar radiation or sunlight which plants use for photosynthesis. Photosynthesis is the process of taking sunlight, water and carbon dioxide and converting it into carbohydrates or energy, with oxygen being an additional by product of this process.

When a plant is not actively producing carbohydrates or enough of them, the plant will start to take away or cannibalize its stored carbohydrates to continue to grow and/or reproduce. In corn, at our current or future growth stages, it will start by pulling from the lower leaves, then stalk to help fill kernels on the ear. If you have enough cloudy or hazy days this will affect yield, but also have a big impact on stalk integrity which will lead to standability issues.

Soybeans react differently to reduced sunlight in that the soybean leaves (think solar panels) at that node make up the vast majority of the collection points for solar radiation and subsequent carbohydrate production at that node. If that portion of the plant does not produce enough carbohydrates, that node will reduce its number of pods and seeds per pod. The more time with reduced photosynthesis and carbohydrate production, the fewer pods and seeds you will see on all nodes on the plant.

Yield loss and standability will be of a greater concern if you have had other pathogens, insects or weather conditions that have added additional stress to the crop besides reduced photosynthesis from cloudy or hazy conditions.


 One of the topics that has come up in the last few years has been higher nighttime temperatures during the grain fill period. The old adage that warm nights make the corn grow or mature faster may be more relevant in the vegetative growth stage (VE-V18). However, once corn hits the reproductive growth stage Tassel/Silking (R1) to Dent (R5), you want the corn plant to cool down at night. When nighttime temperatures do not fall below 72°F, the corn plant does not slow down and will keep on metabolizing sugars at a high rate. (I believe this temperature to be closer to 68°F). This rate of high nighttime metabolism which is termed “Dark Respiration”, causes kernels to fill faster, reduces the grain fill time and makes the plant mature quicker. In my experience it can also reduce test weight.

Yield losses of 2 to 3.6 bushel per acre have been documented for every increase of 1° F over 72°F during nighttime hours. If a corn plant cannot produce enough energy from their leaves to fill these kernels properly, they may not fill all kernels on the ear and may start pulling starches from the stalk or cannibalizing the stalk to fill the remaining kernels on the ear.

It has been my experience that corn plants that have adequate nutrients are better suited to handle the stress of Dark Respiration. These healthier plants tend to have better test weight and standability/harvestability.


Signing your fields is a great way to promote Dairyland Seed products in your area. Field signs for corn, soybeans and alfalfa can be ordered by calling the Dairyland Seed headquarters at 800-236-0163 and ask to speak with Stacy Hendricks or Rita Frank.


 All growers with orders for any Corteva Agriscience brand seed product, regardless of crop or trait (including non-GMO products) need to have a signed Corteva Technology Use Agreement in place by September 1. Growers should sign the Corteva Technology Use Agreement electronically at Signing electronically is preferable, however, paper copies are available at or by calling Rita Frank in the Dairyland Seed West Bend office at 800-236-0163.

Brian WellerDan RitterBranden FursethAmanda Goffnett
Brian Weller
Western Region
Dan Ritter
Central Region
Branden Furseth
Northern Region
Mark Gibson
Eastern Region
Amanda Goffnett
Eastern Region
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