Two years ago Chuck Mansfield thought it was just a fluke when wheat plots at the Southwest Purdue Ag Center near Vincennes that were treated with a fungicide yielded more than varieties which were not treated. But for the third time in a row, yields for varieties treated with a fungicide were better in 2011. And he's talking up to 15 bushels per acre better. Farmer reports for those who have used fungicides applied a the proper time also indicate that the response is consistent, he notes.
The disease that the fungicide is thwarting is head scab. Wheat scab has been a major player in limiting yields during the past two seasons. With the right fungicide applied, most of the disease loss can apparently be eliminated.
However, it's not as simple as just spraying a fungicide anytime you want in the spring, Mansfield observes. It requires a high level of management to know when to spray to prevent scab. "You need to apply within about a four-day window when the plants are flowering," he says. "In this area of the state that is around the last days of April or first few days of May."
Wheat heads tend to start flowering in the center and work their way up and down the head to the ends, he notes. The fungicide must be applied during this period to be effective, he says. If the choice is to be a bit early compared to being a bit late, he prefers going on the early side. The fungicide he applies has two active ingredients to provide good control.
There are resistant varieties to wheat scab on the market, but the varieties that perform best to fungicide are counter-intuitive, he notes. You would expect that susceptible varieties would be helped the most by applying a fungicide. In reality, he's discovered that resistant varieties applied with a fungicide at the proper time make for the best yield combination.
It's an additive effect, Mansfield notes. Resistance is relative, and no varieties currently sold are 100% resistant. But with the addition of the fungicide, the overall control may be about 90%. When applied to susceptible varieties that aren't helping provide any control, it's much tougher to reach anywhere near that level of control, he adds.Farmers can apply the fungicide aerially, leave tram lines and apply by ground, or just run over wheat if they don't have tram lines.