With mosquito-borne diseases (West Nile virus, equine encephalitis, Zika* virus, etc.) becoming increasingly common and worries about sources of stagnant water hosting them in backyards on the rise, it’s nice to know that there is an easy way to make your water garden isn’t to blame.
*The Zika virus is not yet found in North America north of Florida and Texas and is entirely absent from Europe, but mosquito species capable of carrying this disease are present on both continents. Most authorities believe that it is only a matter of time before the virus reaches these areas.
It’s easy enough to control mosquito larvae (and black-fly larvae as well) and thus help cut back on the number of biting adults in your garden. You just have to add Bti (Bacillus thuringiensis israelensis), a beneficial bacterium, to the water.
No, Bti is not a GMO. It’s a naturally occurring, widely distributed bacterium probably already found in swamps and lakes near where you live. By releasing it into your backyard pond, you’re only making sure that it is protected as well. Bti is, of course, organic and is widely accepted in organic gardening.
Bti is specific to mosquito and black-fly larvae and will not harm any other insects. Not only is it safe with bees and butterflies, but won’t even harm other aquatic insects. (Please note that another form of the Bt, Btk [Bacillus thuringiensis kurstaki], is used for the biological control of caterpillars, that is, butterfly larvae.) Nor is it toxic or harmful to fish, birds, amphibians, reptiles, or mammals, including humans and domestic animals.
Bti is found in several formats: granules, powder, floating pellets, etc. Depending on the option chosen, treatments should be repeated approximately every 30 days.
Products containing Bti are found in hardware stores and agricultural coops as well as on the Internet (for example, on Amazon.com). Here are a few of the trademarks offered: MosquitoDunks®, AquaBac and Vectobac.
Finally, here is a more in-depth source of information about Bti: Everything you should know about Bti.