Glacier FarmMedia — As worries persist about herbicide-resistant weeds and insecticide-resistant pests, help can be on the way with more natural means.
Haley Catton, a research scientist with Agriculture and Agri-Food Canada at Lethbridge, says producers need to focus on conserving beneficial insects while simultaneously managing pest insects.
“There are two basic rules: don’t hurt them, and try and help them,” Catton told the Farming Smarter conference and trade show in Lethbridge last month.
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Many beneficial insects help to promote synergies and make the most possible use of other ecosystem service providers. Examples are predators and parasitoids, pollinators, microbes in the soil, decomposers and earthworms that improve soil structure and water filtration.
“There are a whole bunch of these things, and any management decision I make, it’s best to consider on a holistic lens, doing the same whether it’s tillage, irrigate or whatever. Considering them in context of all these different things will be the best decision,” Catton says.
“They call that eco-stacking — stacking this on top of that. Stack the beneficials on the soil microbes, think of it all. I don’t envy farmers, actually, because you have so many decisions to make, and some of them are on a short timeframe. Some of them are on a long timeframe, some of them affect your fields, some may have an effect on regional pest populations.”
Beneficials in the field are either predators or parasitoids. Predators include ladybird beetles, ground beetles, lacewings, syrphid flies, aphid midges and yellow jacket wasps that chase down the cutworms and eat grasshopper eggs.
Parasitoids, meanwhile, lay their eggs inside an insect host such as a cutworm, and the babies will eat the cutworm from the inside out.
“These things are massively important. Beneficials kill pests, they scare pests and change their behaviour,” Catton says. A cereal leaf beetle, for example, “will drop off the leaf if it is scared of a predator, and they eat and poop, which is part of nutrient cycling.”
For wheat stem sawfly, a pest on Prairie farms for more than 100 years, Bracon cephi is a parasitoid.
“It is killing a lot of your sawflies. The adult looks like a wasp and she lays her egg in a wheat stem and the larva feeds inside the wheat stem. That parasitoid will find stems with sawflies in them, sting them from the outside, paralyze the larva, and its babies will eat that larva alive,” Catton says. “It’s actively preventing cutting from your fields, but it’s small and it’s out there.”
Prairie field beneficials are also numerous, with plenty of diversity.
There are more than 200 species of ground beetles in Prairie fields. In recent biodiversity studies, 62 such species were found in Vauxhall plots over four years and more than 37 were found over two years at Lethbridge, while another study Catton is just wrapping up found 82 ground beetle species.
It can be difficult to put a dollar figure on the work done by these beneficial insects, Catton says.
“There are so many variables going on. When a problem is prevented — say, an aphid population is prevented from outbreaking because those ground beetles, those beneficials are eating them — a prevented problem is an invisible problem. There is a lot of work being done by these beneficials that we don’t even notice because it’s not being quantified.”
Catton encourages producers to avoid hurting beneficials by not using insecticides unnecessarily. This can be accomplished via scouting and following economic thresholds. Producers who do need to use insecticides can apply “soft” versions and make sure not to use them when beneficial insects are most vulnerable.
“My talk is not about pollinators, but one way of thinking of protecting pollinators is to not spray when they are out flying, not during those daylight hours,” Catton says.
Averting harm and helping beneficials can include offering an alternative habitat with shelter, nectar, alternative prey and pollen. Finding that balance between weeds/pests and beneficials is key.
“It is good to have some pests around. If you sanitize your fields with no pests, then the predators have nothing to eat. You want low levels of pests around.”
Pest management is a tool box, with many tools available to diversify control, be they cultural, physical, biological or chemical.
“It’s important to have different tools because if all you have is a hammer, then everything looks like a nail,” Catton says, referring to the beneficial and unwanted insects.
“Cultural controls are crop rotations, physical controls are trap crops, biological controls are beneficials, and it interacts heavily with the insecticides. When you spray a pest, most of the insecticides we use are lethal to those beneficials, too.”
The International Organization of Biological Controls has been compiling a list of “softer” insecticides. While not currently done in Canada, Catton says Australian researchers used that data to compile a pesticide toxicity table for beneficials, publishing a paper in 2024.
“They did find some main messages that some insecticides are consistently harder than broader-spectrum and some are soft,” Catton says.
For more informtion about beneficial insects, visit fieldheroes.ca.
