This summer has been a little challenging for families on Bayview Avenue in Richmond Hill, Ont. Most have stopped using their backyards, says Anthony Short, who lives there with his wife and 13-year-old son. Most houses on the suburban street have gardens, but it’s rare these days to see anyone out barbecuing, cutting the grass or weeding. The reason, says Short, is that no one wants to get stung by an aggressive new pest: the European fire ant.
This is a new insect to Canada, and it has a number of characteristics that make it particularly unpleasant. First, its sting causes a painful, itchy red welt that can last for days, even weeks. Also, these ants tend to swarm. Those with infestations often say they’re overrun with thousands of the crawling insects, says Eleanor Groden, director of the School of Biology and Ecology at the University of Maine.
While experts are not sure exactly how or when the species, Myrmica rubra, arrived (the most likely explanation is that it was transported in potted plants and mulch from Europe), they do agree it is spreading. There have been a number of infestations in and around the Greater Toronto Area, in Montreal, New Brunswick and the Bay of Fundy, as well as Halifax, which had its first confirmed case in July. A number of children at the Toronto Montessori School summer camp in Richmond Hill were stung, particularly those lying beside the outdoor pool, says Clarissa Ng, a counsellor there. (The ants prefer the moist vegetation of the outside to people’s homes.) Eight-year-old Sydney Gittens, a Grade 4 student at the school, was stung when she was walking in the playground near the ravine. The ants crawled up her legs and bit her ankles, she says, pointing to a spot just under her white socks. It was really painful, she adds. A school nurse iced the swelling. “There have been a lot of bites this year,” Gittens explains. “We check each other and all look out.”
Halifax resident Linda Alexander has tried a number of different pesticides to eliminate the ants from her backyard, but none has worked. There have been neighbourhood meetings about the insects, and she has sent numerous emails to the city. In her daily battle with the insects, it’s clear who is winning: her two teenage sons — aged 15 and 13 — no longer play in the backyard because they don’t want to get stung, and the family dog, a Labradoodle, is being kept inside. Alexander, who says she has been stung several times, still goes outside to garden, wearing high rubber boots and long gloves, but the ants crawl up her spade “by the hundreds,” making their way underneath her clothing, and stinging.
The insects are difficult to eliminate because they resist the regular ant pesticides, says Groden, who has been studying the species for six years. To be effective, an insecticide must kill the bugs slowly, since a carrier ant must pick up and transport the toxic bait back to the colony in order to infect the majority of the workers and queens that live inside the nests. European fire ants pack closer together than native Canadian species so they are more robust: even when many die, lots survive. Pesticides such as spinosad that work on other types of ants haven’t had much effect, she says. Groden has tried out a number of different chemicals on the species: some lowered the population, but she hasn’t found anything that eradicates them completely. “These ants are very resilient.”
There are also concerns the new species will affect the local ecology. While there isn’t the data to predict exactly what will happen, local plant life could suffer because of insects called homoptera that are protected from predators by the fire ants. (Fire ants like homoptera because they secrete a sugary substance, which the arthropods eat.) Homoptera feed on vegetation, which then weakens and starts to die off.
The European ants also kill off native Canadian ants. They are more aggressive, so they win in the fight for food, and the local ants starve. (They also raid the nests of the native species, killing the queens and workers, and carrying off the brood to eat.) “These ants have no known predators in North America,” Groden explains.
Richmond Hill has tried to eradicate the ants with traps, but it hasn’t made much difference, and the town now has a “wait and see” approach — they are hoping Groden will find the right pesticide. “There is no known way to get rid of them,” says Audrey Hollasch, a director at Parks, Recreation and Culture in Richmond Hill. “At the moment, we are encouraging residents not to go out into the green spaces.”