Canadians don’t usually worry about mosquitoes, ticks or other insects in early March. Yet the abnormally mild winter in the country could see some pests bug people earlier than usual in Canada, some entomologists say.
“With a warming climate, the survival over winter can improve for a number of different species, although the relationship is uncertain and a subject of much research by many,” James Tansey, provincial entomologist with the Saskatchewan Ministry of Agriculture in Regina, said in a video interview with CTVNews.ca.
Alice Sinia, entomologist with pest control company Orkin Canada in Mississauga, Ont., says she expects certain pests to show up earlier than normal and even appear in larger numbers during the spring and summer.
“When the winter is very mild, large pest populations will survive,” Sinia said in a video interview with CTVNews.ca.
Sinia calls winter “Mother Nature’s natural pest control.”
“So when the winters are very cold – lots of snow – it tends to naturally control insect or pest populations, so that really increases the mortality,” Sinia explains. “That means you’re going to have … a relatively small population to start up the spring.”
Overwintering insects appearing
Sinia says the opposite is true when winters are mild.
“Right now, because of the mild winter and warm winter days and bright sunshine, we’re already seeing many overwintering insects such as cluster flies, Box elder bugs, stink bugs, the European firebugs,” she explained.
These insects tend to go into hiding during winter, Sinia said.
“They have a specific biological clock that wakes them up during springtime so that they can go back outside and start their natural cycle,” she explained.
“So with the current temperatures we’ve been having and bright (sunny) days, it confuses the biological clock for these insects. So because of that we’ve already seen these insects coming out from their overwintering sites earlier than usual – so they’re not waiting for spring.”
The early appearance of these insects means they are eventually going to have “a very robust population” by the time spring arrives, she said.
Heather Coatsworth, chief research scientist of the field study section at the Public Health Agency of Canada office in Winnipeg, says it’s too soon to say bugs are emerging earlier than they would in parts of Canada. But she said they are likely to do so because of the warmer weather, along with other factors such as humidity, appropriate places to live, and the availability of plants and animals as food sources.
“From a public health prospective, we’re primarily concerned with mosquitoes and ticks and both of these would be likely to emerge earlier in warmer climates,” she said in a video interview with CTVNews.ca.
“In general, warmer climates mean supporting longer seasons for both ticks and mosquitoes to live in. … It is super ecosystem dependent.”
She says the government is doing mosquito and tick studies across the country to test them for pathogens and determine if they are appearing earlier than usual this time of year.
“It’s going to be long-term studies before we see the true effect of climatic changes on bugs in Canada.”
Wasps and bees
Plants are growing and blooming early because of the mild temperature and are attracting plant-feeding insects, such as wasps and bees, as a result. Unless a heavy snowfall or cold spells occur, Sinia expects to see many insects emerge before spring starts or very early in the spring.
Ants
Pavement ants are already showing up outside, Sinia says. She says these ants tend to emerge when the weather is warmer to forage for food.
“So when it’s cold, they don’t come out that much but because it’s very warm, they tend to come out very early,” she says.
Midges
In certain parts of the country, such as in cities or near lakes, Sinia expects an uptick in midges – possibly clouds of them swarming homes or streets – because of the mild weather.
“The temperatures have really helped midges to survive,” she said. “They don’t bite but they can be a nuisance.”
Rodents
More rodents, such as mice and rats, will survive because of the mild winter, Sinia says. Rodents tend to go inside structures over the winter, but she expects their numbers to go up in early spring.
Ticks
Sinia expects ticks to likely continue increasing in numbers because of the warmer weather.
The blacklegged tick or deer tick has expanded its range over the years across Canada.
“It’s showing up in places where it’s not supposed to be. So with this mild winter, that means again the population is not controlled by nature. They’re going to be expanding their range,” Sinia said.
If more wildlife survive the winter, the ticks could spread further with their host animals and increase in numbers, she said.
Mosquitoes
If there is a lot of rain in the spring, Sinia expects it will help the mosquito population to multiply, since mosquitoes need moisture for their eggs to hatch.
“We can see a high population of mosquitoes early spring towards into the summer – that’s if we have a lot of rain during the spring,” she said.
Mosquitoes that overwinter as adults will survive the mild winter and start breeding early if rainy weather occurs, she adds.
Crop pests
Tansey says certain types of grasshoppers are among the most concerning pests in the Prairies. Due to the excellent conditions for egg laying in a relatively mild winter, he expects “elevated populations” of four species of grasshoppers in parts of those provinces. These types of grasshoppers inflicted a lot of damage to crops such as soybean, canola and wheat across the Prairies last year, he said.
“Grasshoppers really love warm conditions,” he said. “The pest species overwinter as eggs, developing as embryos in the fall. Development pauses in the winter and restarts with warm weather in the spring. Very warm weather in the spring speeds their development and leads to an early hatch.”
Spring of 2023 saw a very early emergence of damaging numbers of two-striped grasshoppers in some parts of Saskatchewan, he said.
Species kill trees
Chris MacQuarrie of Sault Ste. Marie, Ont., research scientist with Natural Resources Canada and past president of the Entomological Society of Canada, says the milder weather will benefit the invasive hemlock woolly adelgid, which kills hemlock trees in old growth forests in Nova Scotia and Ontario. It will also help the spruce budworm, which targets spruce and fir trees across Canada.
These pests could cause major damage economically to Canada’s commercial forestry industry, he said.
“A lot of the success of some of these insects can be attributed to climate change,” MacQuarrie said in a phone interview with CTVNews.ca, noting studies on the species are expected to be completed in the spring and summer.
In Eastern Canada, the emerald ash borer and mountain pine beetle also thrive in warmer weather. Two decades ago, the mountain pine beetle used to only be found in British Columbia, but has since spread to Alberta due in part to climate change, MacQuarrie said.
“There’s a negative impact on forests,” he said. “A lot of these insects kill trees. When that happens, the composition of forests can change and different species can grow (and) lots of dead trees can burn.”
Katie Marshall, associate professor in the department of zoology at the University of British Columbia in Vancouver, says it’s important to determine what warming winters do to bug populations because they have many human implications.
For instance, a warmer winter could mean more forest pests kill trees, which can result in the release of huge amounts of carbon dioxide and possibly increase the risk of forest fires. Mosquitoes and ticks also carry diseases such as Lyme disease and West Nile virus.
