Goss’s wilt, a bacterial corn disease new to Manitoba that can’t be controlled with a fungicide, is widespread throughout the province’s corn belt this year.
Farmers will have to grow tolerant varieties, plant corn less often and step up tillage to keep the potentially devastating disease at bay, Wilt Billing, Pioneer Hi-Bred’s Manitoba agronomist, said in an interview Friday.
“One of the things to corn growers’ benefit this year is that the infection came in about the same time as it did last year (during the first week of August), however the corn (this year) is much more developed so you’re… going to have very little affect on grain fill,” he said.
“If you’re seeing a small patch and damage now, we’re far enough along that the yield hit is not going to be dramatic. But for those fields infected in early August with susceptible varieties those yield penalties could be quite expensive.”
Goss’s wilt can cut yields 50 per cent, according to Vikram Bisht, a plant pathologist with Manitoba Agriculture, Food and Rural Initiatives (MAFRI). The disease has been attacking Nebraska cornfields for 40 years. It was identified for the first the time in Manitoba last year in the Roland area.
The disease gets into corn plants through injuries caused by hail, wind, blowing dirt (sandblasting) or insect feeding. It’s spread through soil, rain splash and infected corn residue that blows to other fields.
Billing said he surveyed 150 Manitoba cornfields recently and detected Goss’s wilt in about half of them.
“The results have been quite surprising,” he said.
“The worst areas we’re finding is Morden to Altona – a little bit south of where we found it last year, although we suspect it was in fields in those areas last year too,” Billing said. “We have found it out near Steinbach in quite a few fields as well as in the traditional area around Carman and Roland.”
Although it’s believed the initial infection blew in from the United States, now that Goss’s wilt is here, future infections will be homegrown, Billing said.
“With Goss’s once you have it, it’s here to stay,” he said. “It’s something producers are going to have to start managing for.”
The bacterium that causes corn leaves to wilt, dry up and die can overwinter in the soil. But the main source for future infection is corn residue, including stubble.
“Looking back at the last couple of winters we’ve had the perfect scenario for the spread of the disease, having so much standing corn or stubble remaining in the field over winter,” Billing said. “It has created an ideal situation for the disease to develop and spread.”
Nebraska corn farmers had some early success in controlling the disease through intensive deep tillage, but now rely more on hybrid selection and rotation.
“One trend is we’re finding it in, or adjacent to, very heavy corn-rotation fields whether it’s corn-on-corn or minimum till with corn every other year – that’s where the worst-infected fields are popping up,” he said.
Pioneer Hi-Bred is screening its corn lines for those tolerant to Goss’s Wilt.
“We’ve got a fairly good grasp on what the disease is and how to create hybrids with good resistance to this disease,” Billing said.
“We’re sitting good, it’s just a matter of getting those hybrids developed for our market and we’re going to do that as fast as we can.”
Other corn companies are doing the same, Bisht said on MAFRI’s website.
Goss’s wilt symptoms include large gray to light yellow lesions with water-soaked margins. Bacterial exudates on diseased leaves dry up on the leaf surfaces and appear shiny in sunlight and appear as dark-coloured “freckles,” Bisht wrote.
Most Manitoba cornfields are looking good thanks to warmer temperatures this year than last or in 2008, Billing said.
“What didn’t handle the early water is generally gone and what is still remaining looks tremendous,” he said.
“From this point on everyday we get (frost-free) is going to be a benefit. A small percentage of the crop you can say has made it. We want to get the majority of the crop to that stage.” [email protected]
“Onetrendiswe’refindingitin,or adjacentto,veryheavycorn-rotationfields whetherit’scorn-on-cornorminimum tillwithcorneveryotheryear.”
– WI LT BILLING, PIONEER HI-BRED