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Plant diseases to look for in 2014

Provincial officials say the story for 2013 was of extremely localized disease 
outbreaks and the one for this coming year could be the arrival of new threats

Last year underscored the need for timely scouting for crop diseases.

“Disease patterns matched the weather,” provincial pathology researcher Mike Harding said at last month’s 2014 Irrigation Update conference. “Different conditions led to serious disease issues in one area and virtually none just 20 miles away.”

For example, cereal leaf spot diseases were widespread especially in spring wheats, less common in winter wheat, but most cases were not severe. In central Alberta, foliar diseases occurred in most barley and wheat crops, and was serious in some fields. The key to control is checking early, said Harding.

“If you see any of the leaf spot symptoms early, before flag leaf or before the canopy is completely closed, you want to protect that flag leaf with a fungicide,” he said.

Ergot was also quite common last year, but not as bad as 2012, said Harding. It was another problem that happened in limited situations. The best protection is the old standby, rotation. But producers who spot the problem can leave grain standing so the wind shakes the ergot bodies out of the heads before combining. They can then mow grass around fields as it heads or combine and bin grain from headlands and other areas close to wild grasses separately from the rest of the field. If all else fails, colour sorting the infested grain can up the grade.

Root rot in pulses, especially peas, came up in both Harding’s presentation and one from Ron Howard, another plant pathology researcher with Alberta Agriculture and Rural Development. The Lethbridge Research Centre surveyed 145 fields and found root rots in 98 per cent of them. Many affected plants had no above-ground symptoms, but others showed yellowing. Affected roots are discoloured, with no nodules and secondary roots are pruned off.

“Some crops were hammered,” said Harding. “Symptoms were the worst in east-central Alberta and lowest in the south. Around the perimeters of waterlogged spots were the worst areas.”

Fusarium head blight is established in the irrigation area, but there was a big increase in grain samples downgraded by Canadian Grain Commission for fusarium-damaged kernels in central Alberta and along the Highway 16 corridor. Howard and Harding worked with seed-testing labs to establish how much of this was actually caused by Fusarium graminearum and found increased levels of the fungus on grain and seed from central Alberta.

“Fusarium head blight isn’t a new disease,” said Howard. “It affects most cereals, cutting yield and quality, and causes stalk and ear rot in corn. We’ve had it all over Alberta. But it’s becoming more common — partly because it thrives in warm, moist conditions, but (also because) the new 15A-DON strain is more aggressive and more toxic.”

Stripe rust was less of a problem than might have been expected, especially after 2012 when it spread all the way to Manitoba, possibly from spores that overwintered in winter wheat rather than blowing directly from the Pacific Northwest. Stripe rust thrives with cool nights and 2013 had relatively few of those.

Clubroot is spreading fast. A province-wide survey identified 418 new infections for a cumulative total of more than 1,500 infected fields found since 2004. But the number is likely significantly higher, Howard and Harding said. In a wet spring such as 2013, the germinating spores can swim in the soil moisture to infect new plants, including weeds. It’s still spreading south, north and east from the Edmonton area. The good news is that there are no reports that clubroot resistance in canola is breaking down.

Blackleg in canola is present in most fields, but often goes unrecognized or misdiagnosed, said Harding.

“Many people aren’t looking for it,” he said. “Get a good set of clippers and check. You could be losing yield.”

Howard warned of diseases that could spread or be accidentally imported into Alberta. The province is developing a real-time database to alert producers to both new diseases and established ones that are on the upswing.

Dwarf bunt has been found in the south Okanagan where it’s quarantined. The bunt has the characteristic oily fish smell, but the spores are highly allergenic and flammable — so much so that smut dust is explosive.

Verticillium wilt is a disease of canola and other broadleaf crops that Howard described as “scary.” The Verticillium fungus that attacks canola is a very aggressive species that’s endemic in Europe.

“Other species of this fungus do well in our environment and we have no resistant canola varieties,” he said.

Pulse crops’ honeymoon could be over. They are susceptible to fungal foliage blights that have become quite prevalent in Saskatchewan. Howard advised to watch for them as well as root rots.

A new insect to Alberta, the potato psyllid, could have a dramatic impact on the potato industry. The psyllid carries ‘zebra chip’ bacteria, which causes dark stripes in the flesh of tubers rendering them unsalable. Zebra chip has spread from Mexico to the southern U.S. and is slowly moving northward. Dan Johnston of the University of Lethbridge is leading a Canada-wide survey for zebra chip and potato psyllids, and is working with plant pathologists and entomologists on a project to exclude the disease and protect southern Alberta’s potato industry.

“The province was relatively free of the disease, but we began to have sporadic outbreaks of the disease between 2010 and 2013,” said Howard. “We found the problem was mainly due to a new tomato strain of the disease that came into Alberta on infected transplants for home gardens. We had an aggressive awareness campaign to get home gardeners and market gardens to dispose of diseased plants in ways that prevent spores from drifting to commercial potato crops.”

Howard urged all producers and agronomists to be vigilant for new diseases, and to be careful of imported plant parts, cuttings and seed. Wildlife, including birds and insects can also transport new disease organisms, as well as farm equipment and vehicles and also tourists who may have travelled to infected areas.

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