As the final days of summer approach in Canada, many people are eager to savour the remaining warm weather and make the most of outdoor activities, however, there’s a persistent threat that can disrupt these plans — the pesky wasp.
Toward the end of summer, wasp populations typically reach their peak as colonies expand in size and the need for food intensifies in preparation for the upcoming winter season.
As the population of wasps grows, so does the potential to get stung. And unlike honeybees, wasps can deliver multiple stings because they don’t leave their stingers behind, explained David Beresford, associate professor in the biology department at Trent University in Oshawa, Ont.
“The wasps, they can tell it’s getting cold, and they need a place to spend the winter,” Beresford said. “So they’re looking for little holes in our shingles, in our eaves, in our decks or our garages, any place they can go to get cover. And so as they’re doing that, it looks like they’re just coming right at us while we step outside.”
Normally wasps are out and about hunting and feeding their larvae and “not paying attention to us,” Beresford said, so there is an “appearance that suddenly the wasps are coming out right where we live.”
Wasps aren’t just searching for a cozy spot for winter hibernation; they also have a keen interest in our meals, be it sizzling meat on the barbecue, a glass of wine or a plate of fruit. This often leads to a flurry of their presence during outdoor gatherings.
Why there are so many wasps in the late summer, early fall
By the time the summer wraps up, wasps have had the entire year to build up their populations, explained Rob Currie, a professor of entomology at the University of Manitoba.
“What happens is each year a colony will start off from a single queen and that single queen will go out and forage,” he said. “She’ll collect some bugs and things to feed to larvae and some nectar and build the nest to the point where it expands gradually through the summer. So as the summer progresses, the size of the nest is becoming larger and larger and larger.”
And when you hit the end of the summer, that’s when the nest size is at its peak.
Another reason for the increase in activity is that, at the end of the summer, food sources, like flowers and insects, start to dry up.
“They start more aggressively looking around for other sources of food. And that’s when they get into kids’ pop drinks, they get into picnics, they get into barbecues — anywhere they can find any kind of food, particularly anything sweet or anything that’s meat or fish,” Currie said.
Are there more wasps this year?
Wasp populations ebb and flow every season, depending on factors such as temperature, food availability and the success of the previous year’s colonies, Currie explained.
“It fluctuates quite a bit,” he said. “And from a Canadian perspective, the answer is quite local.”
For example, he said in Winnipeg it has been a very dry season, so the wasps have been particularly aggressive this year.
“That means that there’s less forage available, they’re seeking other sources more aggressively. So there’s probably some truth to that for most regions of Canada this year,” he added.
How to avoid a wasp sting
There are hundreds of species of wasps living in Canada, with the most common being the yellowjackets, hornets and paper wasps, Beresford explained.
Among these, yellowjacket wasps stand out as both the most common and the most aggressive.
“Those sons of guns, they’ll sting you just because they feel like it. You’ll be at a picnic and they will want to eat your potato salad and it’ll just decide to sting you. The other ones tend to leave you alone and mind their own business unless they feel threatened,” Beresford said.
In North America, yellowjacket wasps are involved in about 70 per cent of the stings to humans. They are often mistaken for bees because of their yellow and black bodies, according to the Canadian Centre for Occupational Health and Safety (CCOHS).
If you want to avoid getting stung, Beresford recommends refraining from swatting them as much as possible.
“If generally you leave them alone, they generally will leave you alone. However, those little pesky yellowjackets, sometimes they seem to go on the attack first on occasion — not always, but on occasion,” he said.
Another mitigation technique involves practising proper sanitation, Currie said.
For example, he said when enjoying a picnic outdoors, ensure that all food is securely stored in containers, promptly clean up any food and then remove all trash, as wasps are naturally drawn to such debris.
“Once they learn that there’s food in a site and that it’s there regularly, they’ll recruit to that site and they’ll come back. So providing nothing for them is the best sort of scenario because then they’ll go away,” he said.
Generally, most stings will only result in a temporary injury — pain, swelling, and skin redness around the sting. However, sometimes the effects can be more severe — even life-threatening, depending on where you are stung and what allergies you have, according to CCOHS.
Wasps act as pollinators
Wasps may have their stingers, but they also have their sweet side.
These flying insects can be beneficial in many ways, Beresford said, especially if you are a gardener.
“Nectar is a really nice sugary drink and it’s full of energy,” he said. “And anything that will go get that can pollinate. Now, the bees are extremely efficient, they’re better at it. But wasps also pollinate, but they have a very shiny, tough outer part of their body. So they don’t tend to carry a lot of pollen. But they will indeed pollinate.”
They also act as pest controls.
Many species of wasps are natural predators of garden pests, including caterpillars, aphids and flies. They help keep these harmful insects in check, reducing the need for chemical pesticides, he said.