Bt: Miracle Organic Pesticide or Potential Environmental Disaster? 


Bt, or Bacillus thuringiensis, has been used in some form or another for almost half a century as a specific pesticide against various insects. For some years, it has been one of the most effective pesticides organic growers can use. Bt is a natural organism found at low levels in soils throughout the world. It works by secreting one or more toxins after being ingested by an insect. The toxins are often specific to a family of insects. It appears not to harm humans or other life forms except for the intended targets.

It’s natural, it’s selective. So, what’s the problem?

Like it or not, we are all part of a big experiment now, as the world’s agricultural and timber industries increasingly rely on applications of different Bt strains to more and more land and estuarine areas. Attempts to moderate the amount of spraying by activist groups throughout the world are met with the unified opposition of drug and pesticide companies and agribusiness.

In the US alone, well in excess of one million acres per year are treated with Btk and Bti pesticides to control gypsy moth, tussock moth, and mosquitoes. Often these applications are in cities or suburban areas. Aerial and ground applications supply more Bt spores in a single breath to inhabitants than they would get by eating a year’s worth of unwashed organic produce. Bt spores infiltrate effectively into closed homes and remain at high concentrations in the air for days after a single spraying.

The wholesale use of Bt pesticides and Bt toxin GM crops (a whole other topic) will also endanger Bt’s use in organic farming, because insects may eventually develop resistance to the natural Bt toxins. This will force growers to use genetically modified and untested (and more expensive) Bt’s.

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