By Martin Nagelkirk, Michigan State University Extension
Wheat is heading in many parts of Michigan, marking the time for growers to decide whether or not to apply a fungicide to combat Fusarium head scab.
Fusarium head scab continues to be Michigan’s most challenging wheat disease. Michigan State University Extension recommends growers consider using fungicides during wheat’s early flowering stage of development when weather conditions are conducive for its development. A fact sheet on managing Fusarium head blight in wheat is available for learning more about the disease and the use of fungicides.
The disease, in general, is favored by moderate temperatures of 56 to 86 degrees Fahrenheit and high relative humidity (particularly in excess of 90 percent) beginning and ending several days on either side of early flowering. The national Fusarium prediction model is available to give a daily risk assessment for specific locals. The model is correct about 75 percent of the time, but growers are also encouraged to consider their own experience and that of local consultants.
Wheat is considered to be at early flowering and ready for a fungicide application for Fusarium head blight when one or more anthers are visible. This often corresponds to two to four days after the head becomes entirely visible.
The best fungicides for reducing Fusarium’s threat to grain quality include Prosaro and Caramba. However, even these products may only reduce the infection level by 40 percent and the associated mycotoxin (D.O.N.) by less than 50 percent. To optimize the benefit of a fungicide treatment against Fusarium, growers should make sure to apply when wheat is in the early flowering stage, depending on air temperature – this is usually three to five days after half of the heads have fully emerged above the flag leaf collar.
The application timing of early flowering mostly targets Fusarium head scab. In practice, however, the cost-effectiveness of using a fungicide at this time is due to the suppression of Fusarium and to one of several leaf diseases that almost inevitably infect the flag leaf and heads during the grain-fill period in Michigan.