Expert sneaks up on wigglers with biocontrol

LANGDON, Alta. — Danielle Grant has learned some tricks in the war against mosquitoes as she attempts to get ahead of the pests before they reach adulthood.

Grant is a private pest management consultant who works with municipalities to control mosquitoes by monitoring stagnant water bodies, collecting samples and applying a biocontrol product to kill the larvae.

She has learned to be quiet and patient when looking for mosquito larvae because they respond to waves and motion. The larvae do their best to avoid her when she takes samples of stagnant water with a small dipper.

“If you cast a shadow on your water, then that instantly alerts them to a predator,” she said.

The larvae will respond by tumbling to the bottom of the water and may not be found, she told an agriculture tour group.

Rather than fogging problem adult mosquitoes, Grant has opted for a granular product that contains a naturally occurring bacteria called bacillus thuringiensis.

The larva eat the bacteria, which in turn destroys their digestive system. It is not harmful to mammals or dragonflies. Grant sprinkles the treatment on the surface of water when she finds larvae.

The treatment is available from farm supply stores in 20 kilogram bags or small bricks that last for 150 days. The granules are spread with a unit that looks like a hand held grass seeder and need to go on standing water.

“They are not going to be on any water source that ripples from waves. Their bodies are so small they can drown easily,” she said.

Mosquito larvae, which are also called wigglers, can live in water for seven to 14 days, depending on water temperature. They come to the surface frequently to breathe and eat algae or other small organisms living in the water.

They molt four times and become a pupa at the last stage.

Mosquito pupae, also called tumblers, live in water for one to four days, floating on the surface and not eating. They dive in a tumbling motion when disturbed and then return to the surface.

The metamorphosis of the mosquito into an adult is completed within the pupal stage.

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