A cross country look at what potato pests and diseases growers can expect in their potato fields for the 2022 growing season.
As the days lengthen and the sun warms, potato producers across the country are gazing at their empty fields and dreaming of the crop to come. Alongside imagining the future crop’s yield potential, however, proactive farmers will be pre-thinking through this year’s disease and pest potential too. Without a weather-predicting crystal ball, it’s hard to know exactly which disease and pests will bite most deeply into Canadian fields. Spud Smart took a look at what the top contenders are this growing season.
Late blight has the potential to cause problems in any and potentially all regions. Even growers in New Brunswick, where the disease hasn’t been detected in the past few years, should be vigilant about scouting. Effective warning systems and changing climatic conditions in certain regions are contributing to a decrease in the number of acres impacted.
“Growers are encouraged not to let down their guard against late blight, which is capable of wiping out an entire potato field in a matter of days and also negatively affecting the quality and storability of tubers,” says Khalil Al-Mughrabi, a potato specialist with New Brunswick’s Ministry of Agriculture, Aquaculture and Fisheries.
Late blight risk is highest in wet weather, especially when nights are cool, days are warm, and humidity stays high. Inoculum can travel long distances, particularly during thunderstorms. Keep an extra careful eye out for infection in protected areas including low-lying parts of the field and areas like treelines where applying fungicide effectively is more difficult.
Researchers are working hard to support producers’ efforts against late blight. A national research program is currently underway aiming to develop new disease management strategies and to assess how effective registered fungicides are against the dominant late blight pathogen strains. In addition, spore trapping programs are in place across the country and data is being shared between provinces to support predictive modeling.
Potato Early Dying
Potato Early Die complex (PED) is another major concern for many Canadian producers, causing significant losses from Manitoba through Atlantic Canada. Researchers believe PED is caused by a combination of pathogens and factors including the Verticillium fungus and the Pratylenchus penetran nematode. The fact that some seed may be physiologically older at seeding because of last year’s challenging growing conditions may make the coming crop more prone to PED, especially if plants then face another hot and dry growing season.
The Fruit and Vegetable Growers of Canada (previously the Canadian Horticultural Council) and various provinces are currently investing significantly into PED research including studying management options. As verticillium is not well controlled by fungicide, alternative control trials including planting various combinations of mustards with high biomass and glucosinolates are being conducted in both Canada and the United States. Cover cropping’s positive impact on soil health appears to make a notable impact to PED control.
Producers across most of Canada should also keep an eye on the weather in relation to early blight. Early blight tends to impact plants stressed by alternating drought and excessive moisture conditions: a pattern that seems increasingly common in many areas of late. Spore trapping is being conducted in multiple regions. For the best defense against early blight, choose resistant varieties and tested seed, and support healthy, consistent crop growth through timely fungicide treatments and a strong nutrition program.
The biggest pest of note across Canada continues to be Colorado potato beetle due to increasing resistance concerns. To stay ahead of potato beetle, it’s critical to monitor resistance and rotate secondary foliar products.
“We’ve gotten very lucky the last number of years where insecticide application at planting has for the most part controlled almost a year-long of potato beetle,” says Dennis Van Dyk, OMAFRA’s vegetable crop specialist. “As we go back to having to spray foliarly again, we really need to emphasize the importance of scouting and correctly timing those sprays, not just doing it based on a calendar, to give the products the best chance to work.”
Aphids should also be top-of-mind for all producers, though whether they prove vectors of crop disease or not depends on which species and how significant the populations the wind blows in.
Regional Canadian Outlook
Alberta is likely to fare better than other provinces once again for potato diseases and pests. Other than late blight, which could appear if Alberta experiences a cool, wet spring, and aphids, which may blow in depending on wind currents, potato producers should face few other major concerns. Most notably, Albertan producers rarely suffer much damage from Colorado potato beetle.
“We’re pretty lucky here,” says Terence Hochstein, executive director of the Potato Growers of Alberta. “We’re spread out so far here and we have long, long rotations, so we have to deal with less than growers do in other provinces.”
After last year’s challenging growing season, many Albertan producers suffered storage issues from heat stressed potatoes. Processors and producers worked diligently to mitigate losses. The good news, Hochstein says, is that seedstock wasn’t nearly as impacted so shouldn’t be unusally prone to disease in-crop.
“Touch wood, but we’re okay so far,” says Hochstein.
In Manitoba, near record snowfalls across much of the province’s prime potato growing land could cause wet soil issues early this growing season which may then translate to higher-than-normal emergence challenges, says Vikram Bisht, a plant pathologist agronomist with the Province of Manitoba.
Notably, blackdot disease has been gaining notoriety as an early robber of yield, says Bisht. Blackdot is an important component of the PED complex but can be managed effectively with early fungicide programs in high-risk fields.
If excess moisture lasts into the growing season, issues with botrytis and white may also take off.
In addition to Colorado potato beetle, European corn borer was an issue in some areas of Manitoba last year and likely will be again this year. Wireworms stayed at low populations levels and were limited to only a few fields in 2021, unlike more major infestations further east.
In Ontario, last fall’s wet conditions meant increased storage issues for many producers. With pink rot, pink eye disorder, and bacterial rots on producers’ minds, fungicide will be a key consideration at planting says Van Dyk.
“Growers will be thinking — I can put Orondis in furrow for pink rot, but that takes it away for use on late blight. Do I use my Orondis application early, or do I save it for later in the season?”
It won’t be an easy decision — though Ontario didn’t face much late blight last year, the wet fall was conducive to disease development and may translate to more issues this year.
Ontario producers should also watch for botrytis vine rot, which Van Dyck says appears to be increasing in recent years.
Ontario enjoyed a fairly easy season last year for pest flareups, with wireworm and leafhoppers at relatively low levels. Producers are starting to more frequently apply secondary foliar sprays for Colorado potato beetle.
Prince Edward Island fields experienced ‘pretty standard’ winter weather, says Lorraine MacKinnon, potato industry coordinator with P.E.I.’s Ministry of Agriculture and Land. Though “the usual suspects” — common scab, potato early dying, and soft rot organisms — are on MacKinnon’s mind, she says there are no indications of increased disease risk so far for the coming season. Due to the Island’s sandy soil, early spring moisture conditions have little impact on seasonal disease.
The elephant in the room for P.E.I. remains potato wart. Despite its enormous impact on marketability, the soil-borne fungus is far from widespread — the Canadian Food Inspection Agency (CFIA) reported its detection in three closely associated fields in the last year, bringing detections to a total of 34 since 2000. Still, due to the trade sensitivity associated with the disease, potato wart will be top-of-mind for P.E.I. producers going into the 2022 growing season. As is the case for any soilborne disease, maintaining proper sanitation is a critical first line of defense against potato wart.
As in other regions, populations of Colorado potato beetle, European corn Borer, aphids, and flea beetles will be dependent on PEI’s summer weather patterns.
Agriculture and Agri-Food Canada and the P.E.I. Department of Agriculture and Land will be collaborating once again on an Island-wide click beetle survey. Conducted every three years, the survey aims to determine whether wireworm populations are increasing or decreasing. MacKinnon says the 2019 population survey showed signs of decline for the first time in a decade of surveying.
In New Brunswick, potato producers should be watching — in addition to PED, late blight and early blight – for Potato Virus Y (PVY), which is a regulated potato disease in the province. New Brunswick’s provincial regulations require seed potatoes undergo lab testing in addition to the visual inspection and certification conducted by CFIA inspectors.
“Any influx of aphids, which are the main victor for the virus, can cause infection which the visual inspection might not be able detect either because infection takes place later in the season after the CFIA visual inspection takes place, or because symptoms expression in the foliage is not clear or strong in certain potato varieties,” says Al-Mughrabi.
Seed potatoes destined for planting in New Brunswick can’t exceed the maximum PVY level set annually by the Minister of Agriculture each year.
Whatever one’s growing region, farming success depends on thoughtful pre-planning, diligent scouting, timely treatments, and – yes – a dash of luck. Best of the season to you!
Header photo — Adult Colorado potato beetles feeding on a potato plant. Photo: Tracy Shinners-Carnelley, Peak of the Market
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