pesticides

The press coverage of the campaign to arrest the spread of the Zika virus and other mosquito-borne diseases is a reminder of a responsibility that we homeowners and gardeners have to our communities: namely, the control of mosquitoes on our homesteads.

Find standing water and eliminate breeding sites
The mosquito species in our area go through their breeding cycle, egg to maturity, in less than two weeks. So control boils down to frequently eliminating any standing water. And that may call for using your imagination, too! Not just dumping or covering unused pots, but discovering where else on the premises water accumulates. Even a hollow tree or temporary puddle can serve as a breeding ground. Look for potential breeding sites around the homestead—places like discarded tires, plant pots, tarps, rain gutters, or low spots in the yard. Empty or flush them out every few days. Don’t overlook the ordinary tasks like changing the water in bird baths almost daily. Besides, the birds will appreciate the fresh water!

What about rain barrels?
Some standing water, such as in rain barrels, may be a necessary part of the landscape. A piece of window screening over a rain barrel inlet can keep mosquitoes from entering in the first place. Screens can clog though and there may be other gaps where mosquitoes can enter. If they do get in, or perhaps as a precautionary measure, an NCSU newsletter suggests the same shock treatment used to decontaminate wells: one-half fluid ounce of bleach per gallon of water to suppress them. The chlorine, about 200 ppm, will dissipate within 48 hours, after which the water should be safe for plants.

Using biological or chemical controls
Another option would be one of the biological larva control products containing Bacillus thuringiensis israelensis (Bti). Mosquito Dunks® or Mosquito Bits® are related to the bacterial pesticides commonly used in the garden against caterpillars. Read the label as you probably don’t need an entire wafer and one dose should least several weeks. The pesticide lies on top of the water, so to get full advantage of it don’t empty the barrel completely. Leave a couple of inches of water at the bottom. Do not use any chemical larvacide for this purpose unless the label states something like “will not affect plants, people, pets, or livestock.”

Incidentally, you’ll also see ads for mosquito traps that use radiant heat, sonic waves, or carbon dioxide. These can be moderately effective in luring mosquitoes, but they are expensive to buy and operate. Electric “bug zappers” are not effective as the majority of insects killed are actually beneficial in some form.

Article written by Glenn Palmer, Extension Master Gardener Volunteer.