Between 2014 and 2018, Ontario floriculture growers increased their use of biological controls to manage pests from 69 percent to 92 percent, says Dr. Rose Buitenhuis, research scientist in biological control at Vineland Research and Innovation Centre (Vineland).
“They have adopted biocontrol as one of their main pest control strategies, and it’s amazing,” she says.
These numbers, from a survey conducted by Vineland, in Lincoln, Ontario, reflect a larger shift among North American greenhouse growers to embracing biocontrol.
Many growers, Buitenhuis says, are influenced by, in order of importance, more pests developing resistance to pesticides; growers choosing to improve upon worker health and safety, which can be a concern with chemical pesticides; and growers and employees not having to adhere to a re-entry or pre-harvest interval.
Better plant health is also another reason for biocontrol adoption, Buitenhuis says. “Spraying — especially if you spray a lot — there’s some phytotoxicity still involved with chemical pesticides, so they just see better plant health,” she says. Other reasons, she says, include consumer demands and the efficacy of biocontrol.
Thrips are one insect pest group with a strong resistance to chemical pesticides, Buitenhuis says. In Canada, compared to the United States, fewer pesticides are registered on thrips, and controlling these insect pests in the Great White North is particularly difficult.
Grower use of biocontrol for thrips has led to a broader adoption of biocontrol methods, Buitenhuis says.
“That was kind of how it all started,” she says. “If you have to do biocontrol for thrips, then you have to do biocontrol for other pests, and probably disease as well, because a lot of the chemistries are less, or not, compatible with biocontrol agents. You can’t be fully chemical for all the rest of the pests and fully bio for thrips. You really have to integrate it, and it can be a puzzle sometimes.”
Finding new means of biocontrol
As the popularity of biocontrol methods grows, Buitenhuis, Vineland horticultural production systems research director Dr. Michael Brownbridge, their teams, and their government and university partners, continue to research biocontrol. And they have made some crucial discoveries along the way.
“In our earlier years, we looked at predators, entomopathogenic fungi and nematodes and all the individual biocontrol agents to really optimize their use,” says Buitenhuis, who has worked at Vineland for nine years. “Right now, we’re also looking for new biocontrol agents to fill the gaps where there’s no biocontrol available.”Discovering new biocontrol agents can involve looking at pests that are not easily suppressed by existing biocontrols, such as pepper weevils and mealybugs, or pests that have not yet arrived in North America, such as the tomato leafminer (Tuta absoluta), which Buitenhuis says has spread throughout the rest of the world.
Finding generalist predators is another avenue for advancing biocontrol developments beyond the use of wasps, beetles, biopesticides, and other beneficial insects and microbes that are already on the market, Buitenhuis says.
“In Europe, they have now these generalist top predators that can eat multiple pests that provide a base layer of protection, and they can stick around in a crop, even if the pest numbers are low, because they can use alternative food sources,” she says.
An example of such a predator is a predatory mite that Buitenhuis and colleagues are working with. At this point, they are looking into how to mass rear enough of the predators so biocontrol companies can sell them to growers.
An easy option: dipping cuttings
Another form of biological controls is cutting dips, whereby growers dip cuttings in biopesticides and insecticidal soaps and oils, to eliminate pests and prevent them from becoming a bigger problem. As with biocontrol in general, about two thirds of floriculture greenhouse growers in Ontario use cutting dips, according to a 2018 Vineland survey.
“It’s a very simple method, very easy to implement, when you receive the cuttings — for example poinsettia or chrysanthemum cuttings — get them out of the bag, dunk them in the solution and then just proceed as usual, sticking them and putting them under mist,” Buitenhuis says.
Vineland is working with Flowers Canada (Ontario) and product manufacturers to include cutting dips for approved use in existing oils, soaps and biopesticides, she says.
While cutting dips have proven effective on thrips and whiteflies, some Vineland research from 2018 has also shown promise with dipping to help eliminate spider mites, Buitenhuis says. “We found in our thrips trials, the plants were also infested with spider mites, so it turned into a double trial by accident,” she says. “It was nice, because we could see that a lot of the products that worked for thrips also worked for spider mites.”
Biocontrol as an integrated system
Over the years, Buitenhuis and her colleagues have found that individual insect pests and biocontrol agents need to be looked at as a holistic system.
“It means looking beyond biocontrols — looking at all the other factors that will have an effect on pests and diseases in crops,” Buitenhuis says. Those factors, she says, may include resistant crops, fertilizer practices, sanitation and how pests come into the greenhouse.
“A lot of growers are very interested in biocontrol and how they can do it,” she says. “Michael and I get invited a lot to different grower meetings in the U.S. to talk about our research, so definitely, the world is changing toward biocontrol and everything that goes with it.”