Should you be applying fungicides to your soybeans? Should you be adding insecticide into as well? You won't find a consistent answer from most Purdue data. You will find anecdotal evidence where farmers think it helped, but most don't even have test plots to compare to when the product or products were applied.
One farmer in central Indiana said last week that he tried a fungicide application a year ago on one very later field of soybeans. Since he didn't have a true plot, he can't say for sure that the application actually paid off. What he noticed and normally what has been observed in other trials is that spraying tends to keep plants healthier longer. There may be as much as a two-week delay in those sprayed soybeans before they're ready to harvest,
The farmer plans to apply some more fungicide on some soybeans this year. But he's still not ready to spray the whole farm. The applications cost money, and he says he' still not sure if there is an economic payoff in every situation.
The fact that the soybeans stayed cleaner and healthier longer confirms what was observed several years ago in plots conducted by Indiana Prairie Farmer and the Tippecanoe County Extension Service. The plots were conducted at the Throckmorton Research Center near Romney. The seed was also of better quality. However, the yield itself was almost the same. Under current methods for marketing, where a premium is not paid for quality soybeans, it becomes harder to justify the extra expenses.
Purdue's results so far indicate that sometimes treatment pays, and sometimes it doesn't pay in terms of dollars and cents, yet sometimes does. Purdue diseases specialists are still trying to learn what happens when fields are sprayed at various stages of reproductive development.
Whether it makes sense to add an insecticide if you're spraying for a fungus may depend on whether insects are present, or not, he says. If the insect is there, it may work. Based on the theory that the bug must be present, sometimes fungicides may need to go on before the insecticide needs to go.