Bill Curran has devoted 18 years to a mystery that’s new to many of us. As lead scientist for Pioneer’s LaSalle, CO, Goss’s wilt hybrid development and screening program, he preaches prevention because there is no remedy.
“Hybrid resistance is the key defense strategy for Goss’s wilt,” Curran advises.He urges growers to scout fields for unusual lesions, and randomly stunted or wilted plants. “Send suspicious leaf samples to a certified university or seed-company laboratory to verify what you have,” he says.
“That part is key because there has sometimes been an overblown assumption that any leaf damage is Goss’s wilt,” says University of Minnesota associate professor â€¨of plant pathology Dean Malvick. These days he spends a lot of time advising crop consultants and growers on Goss’s wilt. “Everyone wants to know how it became so widespread in two years.
Why has it finally crossed the Missouri River and headed east after first being found in Nebraska in the 1960s? Found in Iowa in the early 1980s, why has it re-emerged in the central Corn Belt after a 30-year hiatus?
For Goss’s wilt to explode the way it has in the Corn Belt, “either something brought it in a big way or we’ve had it at low levels for a few years, and weather conditions and increased corn on corn production now fuel its development,” Malvick says.
“Clearly, our farming practices have played a role in the recent outbreak of Goss’s wilt,” says Alison Robertson, Iowa State University Extension plant pathologist.
She describes the perfect storm for Goss’s wilt: Hundreds of thousands of acres of susceptible germplasm. “Add to that warmer temperatures, more continuous corn and high-residue environments hospitable to overwintering inoculum. We’ve done a lot less tillage the past two years,” Robertson says.
“It’s getting wetter in our part of the world, which is more favorable for bacterial production and infection,” Robertson says. “Rain spreads those pathogens. We’ve also had more severe weather. Goss’s wilt requires plant injuries to inoculate the plant with disease.
The earlier in the growing season the disease occurs, the greater effect it will have on yield. Generally, the earlier the infection the greater the risk of a significant yield loss. The bacteria grow inside the plant once the infection has occurred. It doesn’t matter when in the growing season plant injury occurs: “Anytime we get injury, we can get infection if the bacteria is present, Robertson says. “In Nebraska young seedlings can get Goss’s wilt from sandblasting. If we have a hailstorm come through mid-grainfill, we could get Goss’s wilt."
The Goss bacteria (Clavibacter michiganensis subsp. nebraskensis, or Cmn) can spread from field to field in rain droplets or on windborne soil particles and residue, Robertson says.