An unusually warm spring and subsequent high water was noted but didn’t hinder this year’s effort to keep local mosquito populations in hand.
At the recent municipal council meeting, Cheryl Phippen of BWP Consulting Inc, the District of Sicamous’ contractor for mosquito control, provided a report on the service, as well as an update on how the battle has gone this year.
“Fantastic,” commented Phippen, noting she uses the phone calls she receives as a measure.
“When the mosquitoes are out people talk…,” said Phippen. “This year I’ve only had one call and it was actually call saying, ‘Hey, I think I’ve found a new site, would you like to come and look at it.’”
Currently, BWP has 123 sites within the district that it monitors and treats when and as required. Treatment is through the application of the non-toxic Bacillus thuringiensis, which targets only mosquito larvae.
Earlier in her presentation, Phippen provided background information on the difference between “nuisance” and “disease vector” mosquitos. The former lay their eggs in the soil, and the eggs can sit dormant for up to 30 years until they become wet with flood waters and hatch – typically earlier on in the summer. The disease-carrying mosquitoes lay their eggs on the water’s surface every one to two weeks. Their population tends to explode near the end of the summer, but are not typically as bothersome to humans as their nuisance relatives.
“One thing about them is they have a very strong preference not for humans… they have a preference for birds, especially in the case of West Nile Virus, that’s where they get the disease,” said Phippen. “So even though our population of those explodes in late July/August… we typically ignore them.”
Phippen added the female disease vector mosquitos are particularly selective in what they bite, with one locally found species having a preference for birds, and another that only bites frogs.
Reflecting on the season so far, Phippen said this year’s high water behaviours – important to monitor for larviciding – were unlike anything she’s seen in the past. She said the lake shot up in May, going 20 centimetres higher than the peak in May 2015, and then seemingly stopped. Phippen said she and her crew thought that was it.
“And then it started to go up again and up again and up again, and then we got to the middle of June and that’s when it started to drop,” said Phippen. “And that’s what I’d never seen before – it started to drop and then turned around and went up again. Just think of the massive volume of water required to turn that around. So we’ve had a long peak of Shuswap Lake, which impacts a lot of our sites right in town.”
While Sicamous has had it good this year, Phippen said the same hasn’t been so in Revelstoke, where the June flooding from the dam was followed by cooler weather and lots of rain.
“The mosquitoes are vigorous and happy there, and I hear about that,” said Phippen.