Potato growers could soon have some much-needed help in their ongoing battle in the field to prevent the spread of pests and disease.
Potato growers could soon have some additional tools in their relentless battle against in-season pests and disease, thanks to a comprehensive new research project being co-ordinated by the Canadian Potato Council.
The five-year project is being funded by potato producers, industry partners and Agriculture and Agri-Food Canada Growing Forward 2 program through the Canadian Horticultural Council’s Canadian Agri-Science Cluster for Horticulture 2. As part of the agri-science cluster project, researchers from across the country will conduct pest- and disease-specific research in these four key subject areas that have been identified as having a significant impact on the Canadian potato industry:
- Zebra chip/psyllids
- Early dying/Verticillium wilt
- Potato virus Y
Researchers began their work earlier this year and are scheduled to wrap up their efforts in 2018. The aim of the project is to provide growers with additional knowledge that will enable them to implement more effective pest management strategies.
Zebra Chip and Psyllids
Psyllids are small planting-feeding insects responsible for vectoring the pathogen Candidatus Liberibactor into potatoes and causing the black stripes that can been seen within the tubers known as zebra chips. While the infected potatoes still grow to relatively normal size, the black stripes render them unusable.
While there have yet to be any confirmed cases of psyllids carrying the pathogen in Canada, the concern is it’s just a matter of time.
“Clearly if it has moved north as far as Idaho, Oregon and Washington, it’s poised to enter Canada and that’s why there’s concern,” says Dan Johnson, a professor of environmental science at the University of Lethbridge and project lead on the CPC’s psyllids study. Other key researchers on the team include Alberta Agriculture and Rural Development insect management specialist Scott Meers, AAFC potato pathologist Larry Kawchuk, and a network of field specialists in Alberta, New Brunswick, Quebec, Ontario, Manitoba, and other provinces.
“For once we are ahead of the problem. We know they’re coming,” says Johnson. “We want to stay on top of it rather than react later.”
The first priority for Johnson and his team was to set up a monitoring system. As part of this system, yellow sticky cards were sent out to professional field monitors across the country to collect samples. While some psyllids were discovered, none were potato psyllids and none carried the disease that causes zebra chip.
“If we can do regular sampling and field surveys and find out it’s not here yet, that’s good for growers. It means we’re free of the disease,” Johnson says. “On the other hand, if we do find it that’s great because we know exactly where it’s turning up, and we can focus attention there rather than have a panicked, uncertain response.”
As part of the study, Johnson and his team are also looking at ways of treating the weeds that psyllids often live in prior to infecting potatoes. In addition, they are investigating the use of computer mapping to determine exactly where potato psyllids hatch and lay eggs, as well as to develop strategies to target the disease or eliminate the insect carrier.
“The first thing [growers] will gain from the study will be better information. They won’t have to worry that it’s already here or where it might be,” says Johnson, adding that information will allow growers to formulate a more integrated management process that could include bio-based pesticides and other management actions.
“If it does show up, we can track where it came from,” he says. “We can find out more about the source and whether or not that source is carrying the disease or is resistant to certain chemicals. We’ll know much better what we’re faced with in a new enemy.”
Wireworms are thin, hard-bodied larvae of the click beetle that feed on the roots of cereals and other crops including potatoes. They were a huge problem for farmers across the country until the early 1950s when organochlorines such as DDT, Aldrin and Heptachlor were introduced. Those chemicals were later banned in favour of shorter residual organophosphates, which in turn proved to be effective in killing wireworms but were also found to be hazardous for birds.
Bob Vernon, a research scientist with AAFC in Agassiz, B.C., has been studying wireworms for the past 15 years and is heading up that portion of the CHC study. Vernon says the top priority for his team is finding a replacement for Thimet, an organophosphate insecticide that is due to be phased out for use in Canada in 2015. A number of replacements are already being considered and their efficacy will soon be tested at various test plot locations throughout the country.
“We’re looking for an alternative … that wouldn’t require farmers to modify their growing practices a lot,” says Vernon. “In potatoes, it likely wouldn’t be a granular approach. It would probably be a combination of seed treatments on the potato seed in conjunction with spraying of certain new products.”
Vernon and his team are also studying how to kill resident and newly formed wireworm populations (known as neonates) during the planting of cereal crop rotations to prevent their larvae from infecting potato plants in subsequent rotations. Methods for killing the adult click beetles before they lay their eggs in cereals are also being developed.
“If you do that you don’t have a problem in the potatoes two years down the road,” he says. A seed treatment approach would be “a very cost-efficient method for farmers to use and would be adopted immediately if we were to develop a treatment that actually kills the existing wireworm and the newly formed wireworm populations,” Vernon says, adding researchers are also looking at more effective ways of monitoring wireworms and how these methods work with different species, varying soil types and under variable environmental conditions.
Early Dying/Verticillium Wilt
Verticillium is a fungus present in soil that loves to live inside the vascular system that conducts water in plants. It enters a plant through its roots and can plug up the vascular system, preventing the plant from getting the water it needs and causing a host of fungal diseases.
Verticillium is partial to potato plants and can cause them to expire one to three weeks earlier than normal, resulting in smaller than usual tubers. It can have a huge impact on late tuber bulking in processing potatoes used to produce french fries and result in lower prices for growers.
Mario Tenuta, a Canada Research Chair in Applied Soil Ecology at the University of Manitoba and lead researcher on the early dying study, says his group’s top priority is to provide potato growers with a viable, commercial test for detecting the fungus in soil. While some tests already exist, they are expensive, take a long time and are largely unreliable.
“The problem with existing tests is they are not specific to the Verticillium that attacks potatoes,” Tenuta says, adding his study is using DNA to determine the exact species of each sample being studied. “It will show if the Verticillium in the soil attacks potatoes or not. If it’s not the potato kind, you don’t need to do anything. You’ll save time and money.
“Hopefully we can help them make more informed coping strategies. That’s what we’re all about, providing new tools and making them available … so we can empower growers and give them an option to know more about their soil and take action.”
Potato Virus Y
Potato virus Y, or PVY, is a virus vectored from plant to plant by aphids. It is considered one of the most dangerous potato diseases because it can result in both yield and quality loss.
It wasn’t a major concern for Canadian growers in the past, but the efficacy of existing management strategies are challenged by new PVY strains that are more aggressive and can spread more quickly than older strains, as well as the new combination of potato varieties that now characterize the North American potato industry.
“PVY used to cause just mosaic symptoms in [the leaves of] plants,” says Mathuresh Singh, director of agricultural certification services for Potatoes New Brunswick and project lead for the PVY study.
“But with the appearance of these new strains it has also started causing symptoms in tubers which is called potato tuber necrotic ringspot disease. Because of that, it has become much more important.”
Singh says there are three main objectives of his study: to determine the extent of the new PVY strains across the country; to study the symptoms of the new strains in different potato varieties; and determine how best to manage the problem in the future.
“We’re trying to develop science-based, on-farm best management practices. We’re talking about managing this in the field, not in the lab,” he says.
Singh maintains the ultimate goal of his research is to develop strategies tailored to the needs of growers in different regions of the country and the unique environmental and geographic challenges they face. This includes using the results of an earlier study conducted in New Brunswick and seeing if the results can be duplicated in field tests in other potato-growing provinces such as Alberta, B.C., Manitoba, Prince Edward Island and Quebec. Some of the possible solutions that will be studied include earlier management of crops and combining insecticides and mineral oils to discourage aphids from spreading.
“There is no single solution for managing this problem,” Singh says.