by Melanie Jacob
Journal Staff Writer
It seems that if residents aren't getting flooded out of their homes, pesky mosquitoes are chasing them inside. Fortunately, the city has once again implemented their mosquito control program.
The program involves the use of two different types of products that, unlike other pesticides, attacks the larvae rather than adult mosquitoes.
"We use the larvacide in standing water on city property only," said Lawrence Dunne, the facility maintenance manager for the City of Humboldt. "It's a bacterial agent that only attacks mosquito larvae. We have an individual that attempts to go through all the property at least weekly."
The products used have no harmful effects on human or other organisms such as frogs or ducks, although lower numbers of water beetles have been observed. The one product, VectoBac, is used for most areas and lasts up to three days. The other product, Altosid, is used in areas of high concentrations of mosquito larvae and lasts for up to 28 days.
According to Health Canada, all pesticides have to be registered by Health Canada's Pest Management Regulatory Agency (PMRA). Once it has been registered, only those with the appropriate applicator's licence are free to use it according to its labeled directions.
"A registered pesticide has been evaluated by the PMRA for human health, environmental safety, and value," said Sara Lauer, a media relations officer for Health Canada in an emailed response.
Despite the lack of potential health risks, there is also the ecological impact to be aware of. As many people would know, artificially targeting a specific organism in a food chain can have reverberating effects in the entire ecosystem. Nevertheless, even those risks were taken into consideration by Health Canada.
"Health Canada's assessment of Bti (the relevant ingredient in the larvacide) also considered the ecological impact of reducing blackfly and mosquito populations on other organisms that feed on them, including fish and birds," said Lauer in the email. "Health Canada has determined that reduction or removal of biting insects would not likely have a lasting impact on fish or bird populations that may be present because of the likely availability of other food sources such as insects not affected by Bti."
Be that as it may, the city began using the products at the start of summer in May and continues to the beginning of fall, which is usually around October.
Each week, city staff goes to areas of standing water and tests the mosquito count by dipping in a cup. Since the larvae need to attach to the surface to breathe, it's easy to get an idea of how many there are by counting the larvae that end up in the cup. If they count more than three larvae, they'll use the larvacide.
"Mosquitoes can lay eggs in a ditch with water and that ditch can dry up and those eggs can stay there for up to seven years," said Dunne. "Next time that ditch fills with water, those eggs can hatch."
In addition to their enduring hatching abilities, larvae can survive in small puddles of water that are only half an inch deep. Old tires with water collecting on the inside, for example, are excellent breeding grounds for mosquitoes. Those small pools of stagnant water can hold up to thousands of mosquito eggs.
As such, the city strongly urges residents to ensure there is no standing water on their property.
