"We've gotten a lot of questions in this past week from farmers and dealers about the use of fungicides on soybeans, particularly this year given the extremely hot, dry weather situation we've been having," says Tracy Blackmer, director of the On-Farm Network for the Iowa Soybean Association. The questions usually go something like this: "After factoring in the possible influence of this year's weather on yield, does the potential profit of using a fungicide on soybeans increase or decrease?"
Blackmer says, "We've conducted hundreds of fungicide applications trials over the years, all looking at the different factors that might influence a soybean yield increase and/or a profit attributable to using the fungicide. When fungicide is applied to soybeans at the R3 growth stage, the biggest factor has been the price of grain."
The likelihood of a soybean yield response was pretty much the same, no matter what the weather or soil type, or whether the trial was in a high- or low-yielding part of the field, he says. "We have not been able to see big differences in yield based upon rainfall between strips in the same field that received fungicide and those that did not. The average yield response for the R3 applications tended to average between 2 to 3 bushels per acre for most of years."
How to figure fungicide profitability in your decision-making process
To help growers tailor economics into their fungicide decision-making process, the On-Farm Network built a calculator that lets you put in your own price for beans and product and application costs.
"When we began testing fungicides on soybeans, a $6.00 soybean price was reasonable," says Blackmer. "If you plug that price into our fungicide calculator, along with $18 per acre for direct costs, the expected outcome would be a $5.40 per acre loss from using fungicides. But if you put in a bean price of $14 per bushel, and the same $18 per acre for costs, the calculator suggests you could expect an $11.40 per acre profit."
One of the report items generated by the calculator is the number of years you might expect fungicide application to be profitable, based on the bean market price and associated costs you plug into the tool. Many growers are able to keep costs lower by combining a fungicide application with an insecticide application
So, if you've been wondering whether to use a fungicide this year, base your decision not on the weather, but on the probability of a yield increase and your own costs and market price expectations, says Blackmer. You can get that probability number by using the On-Farm Network online fungicide calculator.
Note: If you'd like to dig a little deeper into the research behind the On-Farm Network Fungicide Calculator, you can start with this poster.