AgronomyWinning the Battle Against Late Blight

Winning the Battle Against Late Blight


[deck]How one of the primary scourges of the potato industry is being successfully fought in Alberta.[/deck]

When late blight was discovered in many Alberta potato fields in 2010, growers, scientists and many others in the province’s potato industry were justifiably worried. Its return represented a serious threat to the Alberta potato industry, seeing as the province had been virtually late blight-free since the early 1990s.

Caused by the fungal pathogen Phytophthora infestans, late blight is placed by scientists in a group called oomycetes, which are water moulds. The pathogen is highly aggressive and can potentially infect all plant parts, causing rapid dieback and death. Late blight is known for the extensive damage it can do if allowed to get out of control, not only reducing the yields of potatoes in the field but also causing major losses in tubers in storage.

The disease was responsible, in large part, for the Irish Potato Famine in the 1840s, which resulted in the deaths and mass emigration of millions of people.

The Potato Growers of Alberta takes the threat very seriously and is involved in the late blight battle on several fronts. Thanks to the efforts of a number of stakeholders including potato growers, the association says Alberta growers are winning the battle against late blight in Wild Rose Country.

The PGA is expanding the spore-trapping project it began in 2014, part of a multi-pronged attack that also includes a publicity campaign and a speaker series on the issues surrounding late blight.

A Dacom weather station system — which combines sophisticated sensor technology with Internet and scientific knowledge that growers can use to monitor and fine-tune their production process throughout the season — has also been added to the arsenal of weapons against late blight.

“The hope is we can eradicate it, but it will require a national and North American effort,” says PGA project manager Jay Anderson. “As far as Alberta is concerned, we can eliminate the disease in the field, if not necessarily the pathogen itself.”

Trapping More Spores

The PGA reports that spore trapping has been hugely successful in alerting authorities when the disease is present in a given area. Spore traps detect late blight-causing spores in the air before they infect crops.

“In 2013 we had kind of a rough year with late blight, and it was proposed we come up with a spore trap network — sort of an early warning system for late blight,” Anderson says. “By detecting pathogens in the air we could advise people to tighten their spray program and protect the crop based on what sporangia are flying around in the air.”

In 2014, the PGA activated a network of eight spore traps in the province to forecast potential outbreaks of late blight based on the spore population and also weather conditions.

“From 2013 to 2014, by tightening up spray programs using the data from the spore traps, we delayed the outbreak of late blight by up to three weeks,” Anderson says. As a result of their success, five more traps have been added for a total of 13.

Three of the traps are known as a Rotorod traps or “sticky traps.” They use petroleum jelly on the end of a rod that spins and picks up particulates in the air. The rods are changed every four days, and taken back to a lab where they are analysed for P. infestans spores.

The other 10 traps are Burkard cyclone traps, a kind of volumetric sampler. Using a vacuum, they take in air and deposit it in vials in the head of the trap, with one vial being used per day. “We can go every seven days and collect the vials, and those samples are looked at under a microscope and given a low, medium or high value based on the number of spores collected,” Anderson says, noting the cyclone traps are less labour-intensive than the sticky traps.

As of late August — despite spores being detected at various times in five of the 13 traps — only one case of a late blight outbreak had been reported. The PGA says it was quickly contained.

That one case was only about 70 kilometres southwest of potato fields belonging to Laus Stiekema. He farms about 800 acres of potatoes in Vauxhall, a small southern Alberta town with just under 1,300 people.

“With the prevailing southwest winds, we should have seen it in our area, being so close,” Stiekema says. “We did see a bit of a spike in spore counts, but it’s gone down now.”

He credits the spore-trapping project with helping growers modify their spray programs to help battle late blight spores.

“It’s been a very good program to help us in our effort not to spray more than necessary, and to spray at the right times. It’s a community disease; it’s not just the one person who gets affected — it’s everyone’s problem,” Stiekema says.

Emily Snowdon agrees. The McCain Foods agronomist has a lot of experience dealing with late blight in New Brunswick, so much so that she was called upon to help with the PGA late blight project in Alberta. McCain is providing in-kind support for the PGA project.

“It only takes one spore to cause a problem. I have to hand it to growers; this is a new problem in Alberta but they’ve taken everything they’ve learned to heart. That one case could have been much worse, but they modified their spray programs and took it seriously, and hopefully it’s a done deal for 2015,” she says.

Adding to Arsenal

The addition of the Dacom Agri Yield Managment system, part of an integrated pest management initiative by McCain Foods, is helping supplement the important data provided by the spore traps. The system provides a disease severity index based on a weather forecast, alerts researchers to periods of high late blight infection risk, and tells growers when preventative fungicides should be applied and whether they should be contact or systemic.

The data gathered by the system is communicated to growers through weekly reporting. One Dacom weather monitoring station is now up and running in Chin, Alta., with two more to be added in 2016.

“It helps growers even more to time their spray schedules better,” Snowdon says. “It’s a change in mindset — rather than using the typical seven-day spray schedules, it’s about timing those sprays to the Dacom model in order to maximize the effectiveness of what you’re putting on the crop. It’s like putting your sunscreen on before you go out as opposed to after.”

Snowdon worked with a Dacom system in New Brunswick, where she says many growers use the data it collects to know when to spray.

“We’re trying to use our experiences in New Brunswick and apply them to Alberta,” she says. “The weather in Alberta has definitely been in our favour — disease pressure has been minimized. It’s been really hot and dry which has been helping. The climate is totally different than in Eastern Canada, but if anything it’s a big plus to have that warmer, drier weather here in Alberta.”

She adds that with a few hot, dry years, disease pressure that helps make an ideal environment for late blight can be minimized. “If that one field is all we have this year, it might be easier next year if we don’t have much inoculum floating around.”

Getting Message Out

Efforts to educate growers about late blight also continue, Snowdon says. She refers to a speaker series last winter to educate Alberta growers about how the disease spreads and how it can be prevented from taking hold.

“Their eyes and ears are open, and they’re taking the information and applying it on their farms. They’ve realized how serious of a problem it could potentially be,” she says. “Everyone is working together — it’s a group effort.”

Anderson agrees. “It’s a success story where growers have taken the info available to them — and the data provided by the spore traps and the Dacom system — and used it to mitigate any outbreak or damage that could occur to the crop,” he says.

“That’s one of the wonderful things about agriculture I think. There’s a lot of technology out there, and that gives us a huge advantage. The challenge is you get so much information that you often have to figure out what to do with it, but with the spore trapping project and the Dacom system, they’re both tools where you get the data and you can actually use it. They have a real and meaningful application in the field.”


Educating Gardeners

Jay Anderson, Potato Growers of Alberta project manager, says while it’s crucial to educate potato growers about late blight, it’s just as important to work with the hobby gardening community as well. That’s because tomatoes can also become infected with and spread late blight.

“Through communicating with the garden centres and hobby gardeners, we’ve got late blight resistant tomato varieties in our greenhouses throughout Alberta,” Anderson says.

Laus Stiekema, who farms about 800 acres of potatoes near Vauxhall, Alta., is encouraged to see hobby gardeners brought into the late blight conversation as well.

“If market gardens would go to late blight-resistant tomato varieties, it would help everyone. They would have good tomatoes at the end of the season and help prevent spreading late blight to anyone else in the area,” he says.

Late blight-resistant varieties include Mountain Mist, Defiant PHR, Mountain Merit and Iron Lady. According to Alberta Agriculture and Forestry, greenhouse and garden centre operators might consider growing and offering vegetable transplants of the listed resistant varieties to their clientele, to assist in the reduction of disease in their region.

“We’ve been proactive with retailers to make them aware of the dangers of infected tomato plants,” Stiekema says.


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