An Organic Insecticide
Most gardeners are anxious to get out into their gardens as soon as the weather warms up in the spring and the first green sprouts appear in their gardens. Unfortunately, plant-eating insects are just as anxious as we are to get into the garden. They seem to think that our carefully-tended plants and vegetables were planted for their benefit alone. Bt, or Bacillus thuringiensis, is an organic insecticide that is a useful addition in the gardeners' arsenal against many of these plant-eating insects.
Bt is a naturally occurring bacteria that is common all across the world, and early in the twentieth century it was discovered to be an excellent natural insectide. Bt became available to home gardeners in the 1950s, but in recent years new strains of this organic insecticide have been developed that attack an even wider range of hungry insects.
Bt is an organic insecticide that works by affecting the insects' digestive system. When an insect munches on a plant that has been treated with Bt, the Bt bacteria paralyzes the insect's digestive system and the insect stops feeding and expires from starvation within days.
Because this organic insecticide will kill most any type of caterpillar, it should be used sparingly if you have a butterfly garden or seek to attract more butterflies to your garden. Bt does not discriminate between nasty, damaging caterpillars and the caterpillars that will spin cocoons and emerge as beautiful butterflies.
Another type of Bt, the israelensis strain, will kill the larvae of mosquitoes, black flies and fungus gnats. This is good news for those who suffer through black fly season each summer. To control mosquitoes, Bt is placed into the standing water where mosquitoes breed. For this purpose, the natural insecticide is formulated into granules or solid rings that slowly release the Bt throughout the season. When exposed to sunlight, Bt typically degrades and becomes ineffective after about 24 hours, but in the water it remains viable for much longer. If wet conditions persist for several weeks, more Bt may need to be applied to keep the mosquito population under control. For fungus gnats, Bt is applied as a soil drench when the population becomes evident.
Bt is however, safe to use around birds, bees and pets. Bt breaks down rapidly when exposed to sunlight and it does not persist in the environment. Even though it is safe to use, if the Bt you purchase is in powder form, you should wear a face mask to avoid breathing it in, as you would when working with any other powder.
by Michael J. McGroarty