European fire ants invade Lower Mainland
Experts battling the spread of European fire ants say legislation is needed to halt the movement of soil that is creating new infestations all over southwestern B. C.
“Where the European fire ant has been established, the movement of soil out of the area is going to greatly increase the chance of spreading this ant,” said Rob Higgins, a biologist at Thompson Rivers University.
Potted landscaping plants, soil for lawns and gardens as well as soil excavated from building sites are likely how the insects are spreading in B. C., said Higgins, adding the ants are believed to have arrived here in shipments of landscaping plants from Eastern Canada.
“We have no legislation to control the movement of soil and we’ve heard there are infested areas where they are excavating,” said Jennifer Grenz, project manager for the Invasive Species Council of Metro Vancouver. “Right now there is nothing to stop people taking infested material and dumping it wherever.”
“We’ve let so many invasive species get away on us because we haven’t practised proper prevention,” she said. “Think about property values, if you have an infestation do you have to disclose that when you sell your house? We have one neighbourhood in Deep Cove where everyone is ( building decks) over their backyards, because they can’t even let their dog out in the yard.”
Widespread infestations could also render parks unusable to locals and tourists. Campgrounds in Maine, where the European fire ant was first detected in North America, have been shut down due to infestations, she said.
Grenz and Higgins have communicated their concerns to the government via the InterMinistry Invasive Species Working Group. The province is working with local governments, academic partners and the Invasive Species Council of B. C. to assess the extent of fire ant infestations in B. C. and options to control their spread, according to a statement from the Ministry of Environment.
Though tiny, fire ants swarm quickly when disturbed and deliver a painful sting. They prefer warm, moist locations and spread densely around patio stones and yard structures, with up to four nests per square metre.
Attempts to eradicate European fire ants with pesticides have failed.
“They seem to come back stronger than ever from pesticides,” said Higgins.
In the four years since B. C.’ s first infestation was found in North Vancouver, fire ants have been confirmed in 25 locations on Vancouver Island, across Metro Vancouver and in the Fraser Valley.
“These point locations can be anywhere from half a city block to five city blocks, though the park infestations will be even larger than that,” he said.
The ants are entrenched in a variety of residential neighbourhoods, but also North Vancouver’s Deep Cove Park, Richmond’s McDonald Beach Park, south Burnaby’s GardenWorks garden centre and VanDusen Botanical Garden in Vancouver.
Other communities known to have infestations include Victoria, Oak Bay, Courtenay, Delta, Maple Ridge and Chilliwack.
Grenz worries there may be many more unreported infestations and suggested a rigorous survey of southwestern B. C. is needed to determine the real extent of the problem.
She has been working on control and eradication strategies at a dozen locations with municipalities “desperate” for any answer to the spread of the ants.
“( The Invasive Species Council) has been experimenting with multiple treatment methodologies and we have managed to eradicate them from two sites, one at Deep Cove Park and another pocket at Inter- River Park,” she said.
Digging up nests during the winter months when the ants are inactive allows the entire colony to be removed and then killed in a deep freeze.
“When they are dormant, the ants all cluster up into a fist shape, so we were able to locate nests and dig them up,” she said.
During the summer, the ants burrow and scramble away with egg masses very quickly when disturbed.
“In the summer we removed soil and got eight nests, but in the winter we got 150 nests from the same amount of soil,” Grenz said.
“It really is a lot easier when they aren’t all running around.”
VanDusen Botanical Garden has been digging nests through the winter. Lately they have gone after persistent infestations by raking and burning the nests with propane torches, according to Beryl Zhuang, VanDusen’s acting curator of collections.
The botanical garden is also experimenting with low- tech traps designed by Higgins to lure entire colonies out of their nests and into a plastic container filled with soil and topped with a paving stone that collects and radiates heat from the sun.
GardenWorks has halted the sale of garden soil and bark mulch at the Marine Drive location and disposed of all infested plants after a thorough sweep of the shop since the ants were discovered last year, said merchandise manager Scott Pearce. Additionally, the store will pave a large area to create a physical barrier between the infested area and their products.
The best defence against fire ants is to ensure your yard does not become infested in the first place.
Most government literature on the topic concedes there is no known method for eliminating fire ants once they are established. Instructions are typically confined to controlling their spread and number.
“If you buy a plant or any soil that has any ant activity in it at all, don’t put it in your garden, return it to the source,” Higgins said.