Mosquito control costs council $3.5 million a year.
You’re not imagining it. Brisbane’s mosquito problem is much worse than usual, even after Brisbane City Council’s biggest December mosquito-reduction effort in more than 15 years.
Rain and tide events stretching from mid-November have caused mosquito populations to boom, especially in the city’s north, and the outbreak isn’t likely to end soon.
The notorious salt marsh mosquito is the biggest problem for most residents because it carries Ross River and Bharma Forest viruses.
Council spends $3.5 million a year trying to constrain mosquito populations and sprayed almost 4400 hectares of public land last month alone – the largest December spray since 1998.
Salt marsh mosquitoes usually live about 10-14 days but regular rain and high tides have seen four or five generations overlap.
“You have a variety of other species in Brisbane that can be pests but our worst pest in Brisbane is this salt marsh mosquito,” BCC senior medical entomologist Mike Muller said.
“One reason is you get literally millions of them hatch simultaneously when we get either a tide event or a rain event big enough to flood the areas where their drought-resistant eggs have been left.
“The other reason … is because they’re so mobile – (you can find them) 5kms or more from the breeding site in pest numbers.”
Monday’s rainfall was bad news for bug haters, as it gave salt marsh mosquito larvae another chance to hatch, guaranteeing the outbreak would last for at least another week or two.
Another high tide event in two weeks’ time is likely to extend the infestation towards the end of January as yet another generation hatches.
“They really do thrive on wetting and drying cycles,” Mr Muller said.
“They lay their eggs in and around the margins of the pools as the water level’s dropping and those eggs will then stay viable until the next time they go under water.”
Suburbs near wetland areas such as Sandgate, Brighton, Bracken Ridge and Boondall will be most affected but the council has found the wandering mosquito as far from wetlands as Chermside and Wavell Heights.
The rain is also likely to cause another jump in the numbers of a dozen or so other pest mosquitoes living all over Brisbane.
There’s been no increase in Ross River or Bharma Forest virus yet but the council and Queensland Health are monitoring numbers closely as February-March is usually the time when spikes occur.
Mr Muller encouraged residents to do their part by clearing away anything which could hold water.
The council will carry out more aerial sprays from helicopters on Thursday. The spray used targets larvae, not adult mosquitoes, so as not harm other wildlife.
Cane toad numbers have also increased but a council spokesman said this was a natural rise over summer months.