Stopping Mosquitoes Before They Can Fly

What Larvicide Treatments for Standing Water Are and When They Are the Right Call

Mosquito larvae hang just under the surface of still water, breathing through a tube and feeding on organic material. In warm weather they go from egg to adult in about a week to ten days. Any water that stands that long in summer here can produce mosquitoes, and shaded water on wooded and lakeside lots lasts longest because the sun never dries it. Larvicide interrupts that stage. Depending on the site, the product is either a bacterial larvicide that the larvae ingest, or a growth regulator that keeps them from molting into adults. Both are aimed at the larvae and are placed at the label rate for the volume of water.

The technician chooses the form by the site. Slow release briquettes go in water that stands for weeks, like a pond edge, a drainage box or a low spot that never fully dries, and keep working for a month or more. Granules broadcast over a wet wooded depression treat a wide shallow area. A rain barrel or a stock tank gets a dose sized to the volume. Water that will be gone in a few days is usually not worth treating and is noted instead.

Larvicide is the right call for water you cannot remove and do not want to. It is not the right call for a bucket, a clogged gutter or a tarp, which take thirty seconds to empty. It also does not touch the adults already in the yard. Those are the job of the barrier treatment on the resting foliage. Because larvicide only works where it is placed, breeding sites off the property keep producing, and mosquitoes from there still fly in.

What to expect: the products are placed by hand, with no spraying in this part of the visit. Treated sites are rechecked on each visit through the warm months, since rain refills low spots and a product placed in spring is spent by midsummer. Your technician will tell you which sites were treated and which ones you can deal with yourself.