“For known cases of Goss’s we do have products that will perform and don’t exhibit the symptomology of the disease.”
– WI LT BILLINGS
Manitoba farmers normally have few disease worries with corn, but not anymore.
Last year Goss’s Wilt, a new bacterial disease to Manitoba with the potential to substantially reduce yields and quality, was confirmed in two Rolandarea cornfields. But officials with Pioneer Hi-Bred suspect the disease, better known in Nebraska, has been in the province for a couple of years.
Because Goss’s Wilt is a bacterial disease, fungicides won’t control it. The good news is a combination of deep tillage, crop rotation and disease-resistant hybrids should keep it in check, Scott Heuchelin, a field pathologist with Pioneer Hi-Bred from Johnston, Iowa told farmers Feb. 10 at the Manitoba Special Crops Symposium.
“The hot spot right now (in Manitoba) is Roland and it’s probably going to move to southeast with the wind, but at the same time it can move any direction the wind wants to move the debris, or where man moves it,” he said.
“It’s basically here and we need to manage it. The bacteria are everywhere out there if you have infected fields.”
Goss’s Wilt bacteria survive on infected corn debris and in soil where infected corn was grown. The disease has to enter a plant through a wound, which could be caused by wind battering leaves, blowing dirt (sandblasting) or hail damage.
The disease spreads when infected corn debris or soil is moved by humans with equipment or stover, or by winds blowing infected debris or soil.
Once the disease is in a field future corn crops are likely to become infected too if they are genetically susceptible, Heuchelin said. However, some hybrids are less susceptible than others and Pioneer Hi-Bred has identified some varieties suited to Manitoba that have some tolerance, Pioneer’s area agronomist Wilt Billings said in an interview.
“We have a good grasp on it,” he said. “For known cases of Goss’s we do have products that will perform and don’t exhibit the symptomology of the disease.
“To bury that residue is critical. What we found down in Nebraska where they had over 10 years’ experience with this, cultural
NEW DISEASE: Foliar symptoms caused by Goss’s Wilt. Although its
presence here wasn’t confirmed until last year, officials suspect the bacterial disease, more common to Nebraska, has been in the province for a couple of years.
NEW THREAT: Goss’s Wilt is a corn disease new to Manitoba. Although it can severely reduce
yields and quality, it can be managed, says Scott Heuchelin, a
field pathologist with Pioneer Hi-Bred.
practices will help – covering the debris so the soil can break down that bacteria. But incorporating resistant genetics into your rotation is critical.”
Yields of susceptible corn hybrids can be cut 30 to 40 per cent by Goss’s Wilt, Heuchelin said. If seedlings are infected they can die or become sterile.
If the disease strikes later, it affects the leaves reducing the plant’s capacity to feed itself. The infection can affect the plant’s vascular system, weakening the stock, making it more likely to break in the fall before harvest.
Once a plant becomes infected the lesions produced on leaf surfaces produce bacteria, which in turn can spread to other plants in the field via wind and rain.
Leaf lesions are wide and are brown, yellow, or grey in colour. They may be elliptical or V-shaped and usually extend down a leaf vein.
Where leaves are dying, it’s common to see white freckles and small blotches, Heuchelin said. That’s bacteria oozing from the stomates and drying on the leaf surface. It’s happening during a wet period; it looks glossy, like egg white.
“This bacteria is fairly specific to corn so the longer you can stay away from corn in that particular field the better off you’re going to be at lowering inoculum,” he said. “But that’s not going to be a cure-all because if it’s in your field it’s probably in the neighbour’s field.”
Although deep tillage increases the risk of soil erosion, it is more effective than no or minimum till in reducing the disease, Heuchelin said. The deeper infected corn debris is buried, the more likely it is that soil organisms will destroy it.
“We’re currently screening our shorter-season material,” he said. “Just be aware when you are choosing a hybrid there is such a thing as genetic resistance and it will go a long ways to helping manage this. But you don’t want to rely on that solely. You also want to do best practices as far as your crop management. Along with genetic resistance you want to work in crop rotation.”