Reports of Goss’s wilt in corn are early, but not surprising, according to Holly Derksen, field crop pathologist with Manitoba Agriculture.
One infection was reported near Austin, followed by reports of the disease near Morden.
“Which is not surprising at all,” Derksen said. “We have it everywhere every year, but especially in the Morden, Altona, Carman area, it’s usually quite evident.”
The pathogen commonly presents as tan or grey, often shiny, discolourations on leaf edges, according to the July 26 Manitoba Insect and Disease Update. Lesion edges may appear water soaked or display freckling.
“This sheen is a result of the exudate (exuded fluid) released by the bacterial causal agent. Fungicides are not effective against Goss’s wilt as it is caused by a bacterium,” the update read.
Manitoba Agriculture recommends that producers control Goss’s wilt through crop rotation, variety resistance and residue treatment, although Derksen noted that the latter is difficult.
“I don’t think it’s anything that they aren’t already doing, honestly, for corn,” she said. “Corn residue is hard to deal with. Corn growers are typically using tillage already and things like that.”
The wilt may have yield implications, she noted, but added that total yield loss would depend on the severity of the infection.
“We have had a few years in Manitoba where we definitely have had fields where we have seen, probably, a yield impact and those are often fields that have often had hail damage,” she said.
Hail, sand blasting, wind damage, insect feeding or any other wounds allow the bacteria easier access to the plant and increases susceptibility, she added.
The pathogen is typically observed along edges of the field.
Root rot
Suspected Phytophthora root rot (PRR) continues to be on the list of pathogens causing problems in Manitoba fields this year.
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The disease may cause symptoms in up to 50 per cent of soybean plants and eliminate yield from those plants, the Aug. 2 Manitoba Insect and Disease Update said.
Infections may cause problems for years to come in an infected field and rotations may be insufficient to manage the disease as spores can survive in the soil for years, Manitoba Agriculture notes.
“Seed treatments can be used to manage disease early in the season, and resistant varieties are key to managing PRR,” the province’s website says.
Four distinct races of PRR have been identified in Manitoba and the provincial government has published a list of associated resistant varieties in the Aug. 2 insect and disease update.
