Goss’s wilt can be tackled through good management practices, but it may take genetic resistance to subdue the disease
It’s been four years since Goss’s wilt made its first appearance in Manitoba corn crops, and the disease shows no signs of abating.
“It seems to have spread to most of the grain corn-growing regions of Manitoba,” said Holly Derksen, who spoke about the problem at a recent Special Crops Symposium in Winnipeg.
Derksen, a plant pathologist with Manitoba Agriculture, Food and Rural Initiatives, said at least one producer she’s spoken with lost more than 40 bushels per acre to the disease last summer.
That scenario sounds familiar to Wilt Billing, who has spent the last three years conducting an extensive field survey of Manitoba corn crops.
“The primary purpose was to identify where this disease was and if it was moving,” said DuPont Pioneer area agronomist for eastern Manitoba, adding Goss’s wilt has moved both north and west in the province during that period. It was first detected near Roland.
And although those moves were not substantial, Billing said there is no turning back the clock on Goss’s wilt.
“Once you get it, it’s a bacterial disease and the bacteria doesn’t go away,” he said.
But there are ways to manage the disease, even if there aren’t ways to treat for it in crop.
One method is to reduce the amount of stubble left on fields.
“Anything growers can do to reduce stubble will help, the bacteria thrives on the stubble,” said Billing. “So by leaving it on the field you are basically providing a perfect scenario for the bacteria to multiply.”
Removing stubble won’t eradicate the disease, but can help reduce the severity of an outbreak the following year, he said.
Billing said the only way to truly guard against Goss’s wilt is to use a corn hybrid with resistance to the bacterial infection.
Several seed companies provide varieties with varying levels of resistance to Goss’s wilt, including DuPont Pioneer.
“The best management strategy is selecting genetic resistance to plant in those fields, or fields surrounding areas of known Goss’s wilt,” Billing said.
If producers do go with a resistant variety, Derksen said they should read the fine print carefully, noting there are several different scales used by seed companies to quantify resistance.
“Unfortunately, there isn’t a universal system and there is no third-party data,” she said. “So any data on hybrid resistance can only be compared within a single company, you can’t compare company to company, because they aren’t tested at the same location against each other.”
Derksen added that crop rotation and weed control are important components of reducing the virulence of Goss’s wilt.
Both green and yellow foxtail, and barnyard grass are hosts for Goss’s wilt, so keeping them under control is important, Derksen said.
In order for a corn plant to become infected with Goss’s wilt, it must also have a wound through which the pathogen can enter the plant.
“Often you’ll see it after a storm, if there’s been hail or wind damage,” she said, adding a few weeks after hail is a good time to scout for the disease.
Drier weather has helped lessen the severity of Goss’s wilt in some situations, but won’t prevent an outbreak or the spread of the bacteria from one area to another.
“I would say if you grow grain corn in this province, there is a good chance you are going to see it eventually,” said Derksen. “It’s hard to control.”