Wisconsin winter wheat disease update – May 30, 2018

Damon Smith
UW-Extension Field Crops Pathologist
Damon Smith

Warm weather last week, which continued into this week, has pushed the winter wheat crop in Wisconsin toward heading. Most varieties planted in the southern or south-central region of Wisconsin are heading, with full emergence and anthesis (flowering) beginning by the end of the week. We suspect that winter wheat in the northern and northeastern portions of the Wisconsin wheat belt to not be far behind.

Now is the time to consider your Fusarium head blight (FHB; scab) management strategy. Weather late last week had driven the FHB risk on the Fusarium Head Blight Prediction Center to a high level for susceptible varieties. Extremely hot and dry weather has forced the risk back to “low” today.

Fusarium Head Blight 72-hour forecast for May 30, 2018.

However, 72 hour forecasts show risk increasing to medium in much of the wheat belt with high risk in isolated pockets on susceptible varieties (see figure). Rain today, with continued humidity and temperatures in the 80s F for the rest of the week, will keep risk elevated. Areas near the Lake Michigan shore will likely be at high risk.

A fungicide may be needed especially on susceptible cultivars to control FHB and reduce DON (vomitoxin) contamination. The fungicides Prosaro or Caramba have both performed well on FHB in Wisconsin.

Timing of application of these products is critical. I would urge you to wait until anthesis has begun in your field before applying. We have observed poor control where application of these effective fungicides were made before anthesis. In fact, we have observed improved control of FHB and lower levels of DON in finished grain where fungicide application was delayed four to five days after the beginning of anthesis, compared to applications at the start of anthesis.

Data from a fungicide efficacy trial to support this observation can be found by clicking here and scrolling down to pages 16 and 17. Also, remember that application of fungicides should be made no later than six to seven days after the start of anthesis. After this time, fungicide efficacy on FHB and DON control is much reduced.

Get out there and SCOUT, SCOUT, SCOUT and monitor the FHB Prediction Center!