Organic Mystery

Bt pesticide may not really be an insect killer

Join Our Community of Science Lovers!

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Nichole Broderick thought she knew how Bt toxin worked. After all, the toxic crystal produced by the bacterium Bacillus thuringiensis has been known since at least 1911 and widely used as an organic insecticide since the 1950s. Scientists have even genetically engineered various crops to produce the pesticide. According to the accepted model, Bt toxin punches holes in an insect's gut. These pores either allow the bacterium to infect the insect's blood, the so-called hemolymph, or cause the insect to starve.

So when the University of Wisconsin-Madison graduate student fed the pesticide to gypsy moth caterpillars that had been cleared with antibiotics of other gut bacteria, she expected it to become even more lethal. "Initially I was testing the hypothesis that the gut bacteria were actually protecting the moth from Bt," she recalls. "I found that once they did not have a gut community [of bacteria], I could no longer kill them with Bt."

It’s Time to Stand Up for Science

If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.

I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.

If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.

In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.

There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.

Thank you,

David M. Ewalt, Editor in Chief, Scientific American