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Colder spring may not mean population boom for Vancouver Island mosquitoes

Entomologist discusses weather’s effects on the irritating insect
A colder, wetter spring may not necessarily mean an influx of mosquitoes in Nanaimo and elsewhere in B.C., says an entomologist at the University of B.C. (Stock photo)

Despite a cooler and wetter spring, Vancouver Island might not be in line for excessive mosquitoes this summer, according to an expert.

Rain water does contribute to ideal breeding conditions, said Dan Peach, an entomologist completing a post-doctoral fellowship at UBC, but there are other factors in play when it comes to mosquito population and it remains to be seen if there will be a boom.

“It’s an interesting trade-off … the more water and more moisture means more habitat for mosquitoes,” said Peach. “There are mosquitoes that use temporary water habitats, and so they won’t dry out as quickly. But the flip side of that is because of how cool it’s been, it takes longer for mosquitoes to develop and for those species, which have multiple generations a year, this will hamper their ability to build up their population numbers, so it depends on exactly how those trade-offs will really interact going forward.”

Peach was out collecting specimens two weeks ago that he said he would normally come across in late winter or early spring.

With Environment Canada’s special weather statement forecasting warmer and sunnier weather in the coming days, that might also affect mosquito numbers.

“Last year, they plummeted towards the end of the summer there,” said Peach. “During the heat dome, it really knocked them down. Heat and dryness will kill adult mosquitoes quite well. They desiccate – they dry out and die. It also dries up breeding habitat for them so they can’t reproduce as well.”

A hot, wet summer would likely lead to elevated numbers, the entomologist said.

In terms of mitigating risk of being bitten, Peach recommends disposing of standing water that can accumulate on tarps and in buckets, as that is premium habitat for breeding. A press release from pest control company Orkin Canada recommends trimming vegetation, circulating water in pools, fountains and ponds and using yellow bulbs outdoors, as they are less attractive to mosquitoes.

Peach said wearing light-coloured clothing also helps as female mosquitoes, which are the ones that draw blood, “prefer dark coloration,” and wearing insect repellent or natural alternatives can also be effective.

“Lemongrass and citronella are great, rosemary too,” said Peach. “You kind of want a bunch of those things.”

He also pointed out the insects also get a bad rap and have ecological benefit. They’re pollinators and a food source, with bats, spiders, fish, birds, frogs, dragonflies and their larvae and predaceous diving beetles among the species feeding on mosquitoes or their larvae.

“Larval mosquitoes are filter feeders and in some ways, they’re helping to convert solar energy from the sun into biomass,” said Peach. “So the larvae will eat algae, and decomposing organic matter and they’ll convert that into insect biomass … and either something eats them or they die somewhere and decompose. In either case, that’s helping to transfer nutrients from solar energy into biomass. So you think of the sheer number of mosquitoes in some environments, and there might be a lot at play there.”

Peach seeks assistance for his research. He asks people put “squished” mosquitoes on a piece of paper, include date of collection and address, cross-street or coordinates from Google Maps, and mail to Ben Matthews Lab, UBC Department of Zoology, 4200-6270 University Blvd., Vancouver, B.C., V6T 1Z4.

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Karl Yu

About the Author: Karl Yu

I joined Black Press in 2010 and cover education, court and RDN. I am a Ma Murray and CCNA award winner.
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