Get set to count bodies on sticky traps.
It’s not everybody’s idea of a summer job, yet dozens apply for the painstaking work of identifying insect pests at the Muck Crops Research Station, Bradford, Ontario. Know the difference between a carrot rust fly and a carrot weevil? Better yet, can you differentiate between the damage of the larvae? You’re hired.
“Not much has changed,” says Dr. Mary Ruth McDonald, professor of plant agriculture at the University of Guelph since 1997. “We’re still training summer students to identify insects and diseases. We thought drones with their aerial imagery would have a promising future, but there are still wrinkles to be sorted out.”
These rituals are the basis of Integrated Pest Management (IPM) for onion and carrot growers, mostly resident in Ontario and Quebec. Together, they steward 20,000 acres of carrots and 13,400 acres of onions using IPM strategies: genetic, cultural, physical, biological and if necessary, chemical. Pesticides are a last resort. Growers rely on the crop scouts to say when an economic threshold has been exceeded and when it’s time to spray with reduced-risk insecticides.
Onion and carrot grower Kyle Horlings is a neighbour to the Muck Crops Research Station. He knows first-hand how valuable the weekly crop scouting is, in addition to replicated, annual research trials. He cites the example of several years of fumigant testing with chloropicrin (Pic-Plus).
“Instead of using a broadcast fumigant, we now use a site-specific fumigant in the hill of the carrot to kill nematodes and Pythium,” he says. “We’ve seen better crop yields in the Marsh.”
These refined crop protection strategies are working. In 2019, the weather was such in Ontario’s Holland Marsh that no insecticides were recommended for onion thrips or fungicides for downy mildew. It was too cool and dry. Because thrips counts remained below the spray threshold, growers saved four to six insecticide sprays. In the case of downy mildew, growers had a savings of four to eight fungicide sprays.
In previous outbreaks of thrips, the grower would spray the same insecticide twice, then change to a different mode of action. This targets a single generation with a single insecticide. The next generation of thrips would be exposed to a different mode of action. With this tailored recommendation, the spray threshold can now be increased from one to three thrips per leaf. A biological control fungus has been tested but is not effective.
This case study was shared by Dr. McDonald in her ‘back to the future’ presentation at the McGill Sustainability Research Symposium on January 30.
“Ten years ago, I thought that the future of plant protection revolved around more and better reduced-risk pesticides and improvements in IPM monitoring methods and programs,” she said. “Now there are so many more options.”
Here are five ways crop protection is changing.
New equipment for new disease
Spore traps have modernized in that they collect spores in vials that are checked daily. Through DNA extraction, the spores can be identified and quantified as to whether thresholds are high enough to warrant spraying. This equipment is proving helpful with a new foliar disease, Stemphylium leaf blight which has emerged only in the last decade in onions.
“It’s still a puzzle,” explains McDonald, referring to the rise of Stemphylium. “We’re not sure if it’s global warming. It tends to develop in warmer temperatures but we also see it at cooler temperatures. With enough warm growing seasons, maybe there are enough pathogens to overwinter.”
This disease has proven tough to control, showing resistance to commonly used fungicides. Even some new products are not as effective as they should be.
Growers are now fortunate to source onion seed from California that has been pre-treated with a microscopic coating of insecticide to fight against onion maggot. This delivery system means that growers don’t have to handle the insecticide application. Additionally, a much smaller amount of insecticide is used and targeted.
Marker assisted selection
Plant genetics are progressing rapidly for better resistance to insects and diseases. Similar genetics but with different genes for disease resistance should slow the development of plant disease epidemics. Another interesting development is that vegetables are bred to emerge faster so that they can outcompete weeds. This is an important part of breeding carrots for organic production.
McDonald foresees more use of small, self-propelled equipment, some using solar power. Planters, harvesters, monitors and sprayers will be highly efficient and able to work day and night. Spacing can vary so that plants can be seeded and harvested as needed, at optimum timing. Monitoring can be site-specific to an individual plant or leaf. If sprays are needed, they can be applied to very small, specific areas or to the whole field.
More and more, robotic weeders are being adopted for physical, non-chemical control of weeds. A robotic weeder made by Nexus in Nova Scotia will be tested in Ontario’s Holland Marsh in 2020.
Kevin Vander Kooi, research technician for the Muck Crops Research Station since 1997, grew up in the Marsh and has witnessed many changes over the years. The forecasting systems for disease have evolved and improved with new equipment. Resistant weeds, particularly pigweed, are becoming troublesome. He’s worried about the lack of herbicides to control pigweed in carrots.
What has changed the most is the way in which information is communicated to growers through Twitter (@MuckIPM) and a website: www.uoguelphca/muckcrop/.
“We had an Agri-phone with a pre-recorded message and a dedicated phone line,” says Vander Kooi. “And we used to fax. That’s all changed. We are emailing, texting, posting to a Twitter account and website.”
Next-generation grower Kyle Horlings surfs all of these channels, but most surprising perhaps, is that he still believes in face-to-face encounters. “There’s an open-door concept at the Muck Crops Research Station so I drop in all the time to talk to the station manager, the IPM coordinator, the vegetable specialist. I have a very high trust level in what they are telling me.”
“The station is of the utmost importance to growers,” he continues. “The research grants to the station allow all of us to benefit.”
Karen Davidson, editor of The Grower, goes "Behind The Scenes" of the March cover story titled 'The future of IPM: something old, something new' and speaks with Dr. Mary Ruth McDonald, professor of plant agriculture, University of Guelph. McDonald shares her observations over a 20-year-plus career. Click to listen.