Last Winter Won’t Chill 2014 Fungal Disease

Remember last winter’s chill that cut through your Carhartts? Unfortunately, it didn’t chill the fungal disease pathogens that threaten your corn and soybeans in 2014. Pathogens that cause diseases like Gray Leaf Spot in corn and white mold in soybeans have structures that allow them to overwinter. 

These pathogens can survive even the most bone-chilling temperatures. “When we store pathogens in the lab, we put them in a freezer at -80 degrees Celsius (-176 degrees Fahrenheit),” says Carl Bradley, University of Illinois Extension plant pathologist. “So in most cases, last winter’s cold temperatures won’t have that big of an impact.”

One exception is rust. “Rust pathogens generally don’t overwinter in northern states,” says Bradley. “In corn, southern rust and common rust blow up from southern states. They overwinter on something else than the crop, just as soybean rust overwinters on kudzu. Those states also were cold last winter. So there might be some impact on those diseases.” 

Stewart’s Wilt

One disease where there may be some impact is a bacterial corn disease called Stewart’s Wilt. This disease, which overwinters in the gut of corn flea beetles, is vectored by these beetles on corn the following year.  

There’s a model that correlates the incidence of Stewart’s Wilt on flea beetles survival based on overwinter temperatures, says Bradley. The model shows that cold winter temperatures can dent flea beetle survival. This can translate into less Stewart’s Wilt the following year.