Dipping for Larva!

August 5, 2008

Last Thursday I went to see how mosquito larva surveillance is done. This included looking for mosquito larva in water that had collected in ditches as well as treating some standing water where there was a lot of larva. I was taught by the experts from the Canadian Centre for Mosquito Management. They are the ones who do all the mosquito larval surveillance for Perth County.

Mosquito larva can be found in standing water and catch basins. Standing water includes ponds, ditches, puddles and any body of water that is stagnant and not moving. Catch basins are the part of the sewer system that collects water. In order to determine the presence and density of mosquito larva in the water, you have to do a ‘dip’. Basically you have a little cup on the end of a long stick and you dip it in the water then look in to see if there is larva.

The best way I can describe the larva to you is that they look kind of like sea monkeys. They float at the top of the surface to get air and start out very small. They grow larger until they roll into a comma shape and get ready to emerge. They are actually pretty cute in the water but, of course, they grow up to be what we know as mosquitoes, which aren’t so cute!

If you have any standing water on your property – like in bird baths or flower pot trays - make sure you dump it once a week, or if you have a pond, put in an aerator to keep the water moving. Also, get rid of pools of standing water by filling in the depression. Mosquitoes need between 7 to 14 days to grow from eggs into adults. As long as the water is moving or changed regularly, the mosquitoes won’t be able to complete their life cycles.

There is still no West Nile virus found in Perth County yet. So remember until next time …clean up and cover up to keep WNV away!

Joanna MacDonald