While the good news for Illinois wheat growers is that fusarium head blight (FHB) has not been a significant issue the last three years, challenges remain to its management in the future.
Nathan Kleczewski, University of Illinois Extension field crop pathologist, speaking during the first session of the 2021 Double-Crop Farmers Forum sponsored by ISA, the Illinois Wheat Association and others, says no new fungicides are available today, but new moderately resistant varieties are coming.
Kleczewski says the fusarium pathogen that causes the fungal disease overwinters in crop residues, primarily corn and wheat residues. Wheat behind corn raises the highest risk, while planting after soybeans helps keep the disease at bay.
The thing to watch for every season is wet, warm weather. That combination wakes up the pathogen, which will launch spores into the atmosphere at night that end up raining on wheat heads. Other spores can attach via rain splash and colonize on the wheat head.
“During heading and flowering, wheat is susceptible to the disease. FHB chokes off water and nutrients, which ultimately reduces test weight and yield and can create vomitoxin,” he says. Vomitoxin, if consumed in affected grain, can threaten human and animal health.
FHB is a tough one to treat. Wheat doesn’t flower at the same time in a field. Plants may develop secondary tillers right away or several days after primary tillers. So, if a fungicide is applied, it won’t hit all plants at the most susceptible stage. Generally, farmers may only see 50 percent FHB suppression. Likewise, there may only be 40-45 percent reduction in vomitoxin levels.
“It’s a tool (fungicides). It’s part of the answer but it is not the answer,” he says. “So, it is best to use a combination of moderately resistant varieties and fungicides.”
Kleczewski has performed research looking at timing and rates of fungicide applications. His work confirms not to expect any differences in efficacy with different rates during the labeled application window for such products as Prosaro, Caramba and Miravis Ace. Yields also appear to be unaffected. He recommends scouting for fusarium about 18 days after flowering begins. First signs of disease will be premature bleaching and salmon-colored structures on the glumes.
“You will see things popping out and be able to see if you are going to have a severe FHB issue,” he says. “It takes a few days for the disease to really take off.”
Feekes growth stage 10.5.1 may be a good time to treat via air or a ground rig. Kleczewski says treatment costs vary, so consult a dealer about any offers they may have. He adds that farmers should be on the lookout for leaf and glume blotch, too, where there is lots of residue in a field. It also can reduce yield and test weights, and fungicides used for FHB may be the best option.
“New fungicides are a couple of years away. They look promising and I am encouraged more tools are coming that can be used with moderately resistant varieties,” he says.
Click here to watch the recorded session of the Double Crop Farmers Forum.