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  • Writer's pictureRachel

Soybean Fungicide Applications, 2018 Results and 4 year summary

Sometimes its just hard to believe how fast the time goes. Believe it or not, its time to talk soybean fungicides again. Before you hit the back arrow and skip this article, hang in there: WE HAVE NEW INFORMATION. This blog will hit the high notes of what you need to know about soybean diseases, the results from our 2018 studies, and the economics of ground vs aerial application.

The Background

For a more complete discussion of foliar fungicides in soybeans, check out last summers blog post entitled Foliar Fungicides: Take 2. Soybeans. I’ll take a few minutes to highlight some of the important info before before we head into our results.

1. You can only control fungal diseases with a fungicide. Bacterial diseases like bacterial blight or viral diseases like soybean vein necrosis will not be controlled. We can control diseases like cercospora, frogeye, Septoria, and soybean rust.

2. If the fungal disease is in the roots, like charcoal rot or SDS, it won’t be controlled by a fungicide.

3. Diseases can cause a yield reduction by reducing the amount of leaf surface area for photosynthesis.

4. Infection depends largely on the weather. Wet humid= more likely infection will occur. Hot and dry=not as likely.

5. Foliar fungicides can increase plant health and provide physiological benefits including increased flowering, pod fill and delay in leaf loss.

6. Pioneer trials show an increased yield of 2.6 bushels per acre when using a fungicide. The combined effect of fungicide and insecticide was 5.3 bushels per acre.

7. Local results from 2015, 2016, and 2017 showed a yield increase between 2.4-10.9 bushels per acre by using both fungicide and insecticide at R3. The average across those three years was 5.9 bushels per acre.

8. Breakeven yield is around 3.5 bushels. In the past we have been able to meet and exceed that mark.

9. This a good opportunity to use your CortevaCash and TruChoice programs! Approach Prima works excellent for control of a broad range of soybean fungal diseases.

2018 Results

I’m going to just start with saying 2018 was not a good year to test ANYTHING. Due to high variability in yields across fields we really didn’t see a defined difference in treatments across fields. Specific fields did show higher yields when fungicide was applied but overall, results were mixed. There was a $32 per acre increase in the Marginal Net Return, however extraneous noise prevents us from knowing if this was from the treatment or other factors such as weather, soil, or other management practices.

Across All Years


When we include 2018 with our prior years of study we can see that our fungicide treatment averaged 63.35 bushels while our no fungicide treatment averaged 56.7 bushels. This is an 8.6 bushel yield difference. This average return would easily cover the cost of application. Statistically, we are 99% confident that the difference in these results is due to the treatment and not any other variability in field conditions, management practices, or environmental variation.

Marginal Net Return

Marginal Net Return of treatments was calculated based on $22.50 product and application cost, assuming an average of $12 for fungicide treatment and $6 for insecticide treatment. Additionally, a $4.50 application fee was assumed to account for the average of aerial vs ground application costs. Application costs for no treatment were assumed to be $0.

The marginal net return for the treated groups were $496.99 while the marginal net return for the untreated control group was $464.77. To pay for the cost of treatment, approximately 2.7 bushels are needed. The average yield of the treatment group was 4 bushels above the breakeven bushels and resulted in an additional $32.22 in marginal net return.

Application Method

The two methods of application each have staunch supporters, and when it comes right down to it, do the method that will get the product on the field and that you are most comfortable with. But since we get this question frequently, here is some summaries from K-State and Pioneer about different application methods.

Both methods have their advantages. Aerial application can cover a lot of acres quickly. Additionally, there is no damage from tracks through the field. With ground application, there is less change of spray drifting off target and perhaps greater control over when applications occur.

A large concern with ground application is wheel tracks. Table 1 shows the percent portion of the field impacted by wheel tracks with varying tire and boom widths. K-State points out that area trafficked doesn’t equal amount of yield loss. The plants next to the wheel track may set more pods or have heavier test weight in compensation, and some of the plants in the track will survive and contribute to yield.

When calculating out the costs between aerial application and ground application, often times no cost will be assigned to the cost of operating your own sprayer, both to the machine and labor costs for the operator. Be sure to include the value for a true cost comparison.

Table from KState Agronomy:

If you are interested in comparing the various application methods, let us know and we can set up a field study to test it out!


When we look at an aggregate of all the years, we have a yield increase of over 6.5 bushels per acre. Similarly, we have an increase in marginal net return of over $32 per acre. However, when we look year by year, the results are a little different, likely due to influence of weather and pest pressures from year to year. In three of the four years analyzed there was a difference in yield between treatments. Only in 2018 was there no difference in yield between treatments. Concerning marginal net return, there was no difference in treatments in three of the years. Only in 2016 did we see a difference in marginal net return between treatments of over $67 per acre.

In the long run, it appears that the yield between treatments is fairly consistent. With this in mind, applying fungicide yearly should be a priority. When considering return on investment, keep in mind that while totaling all four years resulted in an increase in marginal net return, year by year results only showed that it paid to apply in a single year. It is important to consider your fungicide a long term investment.

Any questions? Read our Soybean Fungicide Summary Results or get a hold of a Pederson Seed Agronomist to find out what fungicides can do for you!


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