Winnipeg's larviciding crews will be working 18-hour days over the next week to combat what could be a huge emergence of mosquitoes.
Ken Nawolsky, the city's insect control branch superintendent, said the weekend rains have revived mosquito eggs that have been dormant for the past three to five years.
"We're putting all our forces out there," Nawolsky said Tuesday. "We're trying to do our best and fight this battle that we have with this significant amount of rain."
Nawolsky said there is a large amount of standing water on private property, adding property owners need to drain the water or treat it to prevent the emergence of mosquitoes.
"The eggs that have laid dormant for the last three to five years have hatched in the water because of the significant amount of rainfall," he said.
The four helicopters the city uses in its larviciding program were grounded Tuesday because of high winds and low cloud cover, but Nawolsky said ground crews are busy at work.
The helicopters carry out 75 per cent of the larviciding treatment.
Fogging in the city won't begin until conditions match criteria in the city's environmental licences: two consecutive nights in which the city-wide average trap count is at least 25, with a trap count of a minimum of 100 in at least one part of the city.
Nawolsky said Tuesday's average citywide trap count was nine, with the worst area at Brookside cemetery, where the count was 99. Nawolsky said he's convinced the high count at the cemetery is due to mosquitoes being blown into the city by last week's high winds, adding Brookside is ideally situated to catch mosquitoes in that manner.
The next highest trap counts were reported at Assiniboine Park and Kildonan Park, with 25, he said.
Nawolsky said the weekend rain hit Winnipeg at the end of the three-week life cycle of the season's first mosquito outbreak and created conditions that could see a large mosquito infestation unleashed on the city.
Nawolsky said he went to a friend's yard in Charleswood that was dotted with standing water, where he scooped out a small container of surface water that contained more than 200 mosquito larvae, adding he estimated there were more than 5,000 larvae in that backyard.
"These eggs will emerge in seven to 10 days, weather dependent," he said. "We need people's co-operation in helping to look for standing water sites.
"If we get sites like this that aren't being treated, it will have a significant impact on the emergence."
The city will need perfect weather conditions -- low winds, temperatures in the low 20s, no rain -- to conduct the ideal larviciding effort. With rain in the forecast for Thursday, Nawolsky said areas that have been larvicided will have to be redone if the city gets too much rain that dilutes the larviciding product.
"We're hoping the rain stops and doesn't dilute the biological product we've already put out there," he said.
Nawolsky said property owners should check their yards for standing water that collects in low-lying areas, eavestroughs and empty containers.
The water should be emptied or drained, he said, and if that's not possible, the owners should treat the water with a biological larvicide product.