Weaning Winnipeg off malathion will come with a hefty price tag: It will cost four times as much to replace the chemical mosquito-killing agent with a biological fogging alternative.
If mosquito trap counts rise high enough this summer to warrant a nuisance-mosquito fogging program, Winnipeg's insect control branch plans to test a biological fogging agent called Pyrocide ULV 7067.
For decades, Winnipeg has killed adult nuisance mosquitoes with malathion, an organophosphate that's approved for use as a pesticide but is considered toxic to a wide spectrum of invertebrates.
Pyrocide is considered a less harmful alternative because it breaks down more quickly in the environment and is effective at lower concentrations. Pyrocide's active ingredients are one part pyrethrin (a neurotoxin derived from chrysanthemum plants) and five parts piperonyl butoxide, a sassafras derivative that increases the killing power of insecticides by turning off enzymes that help mosquitoes fight off chemical attacks.
City entomologist Taz Stuart has been preparing to test Pyrocide since 2011, but there was no need to fog for nuisance mosquitoes that summer or in 2012. If a fogging program is warranted this summer, the insect control branch will spray Pyrocide in as many as one quarter of Winnipeg's insect-management areas and compare its effectiveness with that of malathion, which will be sprayed in other regions.
Even if the test proves Pyrocide is as effective as malathion, Stuart cannot simply stop using the controversial chemical. That's partly because the province requires the city to use malathion for any West Nile virus control program.
The other potential barrier is financial. It will cost about $400,000 to fog all of Winnipeg with Pyrocide compared to about $100,000 to fog the city with malathion, Stuart said Tuesday
The increased cost is not due to the purchase price of the biological pesticide, but higher labour and fuel costs from how it is dispersed.
Malathion trucks can drive down city streets at 15 to 20 km/h. Fogging trucks spraying Pyrocide, however, must travel at five km/h for the pesticide to be effective, Stuart said. Hence the higher operating cost.
Every year, the city sets aside $8.4 million for insect control and typically spends 90 per cent or more of it on mosquito larviciding and fogging. Although the actual bug-fighting budget varies from year to year, the decision to devote more money to fogging would be political.
If Pyrocide proves effective during a summer test, council would face a decision at budget time the following winter.
Fort Rouge Coun. Jenny Gerbasi, who used to chair a council committee on pesticide use, said she would support spending more money on a pesticide believed to be easier on the environment.
"The use of chemicals in our environment is a very serious issue. I think it is important to do something to protect the public health," she said. "It costs more, but sometimes you have to pay the price for doing the right thing."
The city intends to stop using chemical larvicides completely in 2014, but there is no deadline for using malathion to kill adult mosquitoes.
There may be less need, however, as climate-change projections suggest southern Manitoba may be in for more of the hot, dry summers that are less conducive to mosquito development.
Winnipeg last fogged for nuisance mosquitoes in 2010. Fogging only begins if the city-wide average mosquito trap count exceeds 25 adult females for two days in a row and one quadrant of the city has an average in excess of 100.
The city-wide trap count Tuesday was 15.