Cornell Study Shows Insects Developing Resistance to Bt Crops

[confludemocrat]

For decades organic growers have relied on a soil bacterium called Bacillus thuringiensis (Bt) as an effective yet safe pesticide. Because it degenerates rapidly in the environment, insect populations have never developed resistance to it and it remains an important control for many pests. Understanding the effectiveness of this ecologically benign control, genetic engineers have inserted genes for the bacterium in a wide variety of plants to essentially turn the plant itself into a pesticide. Since 1996, Bt Corn and cotton have been grown widely, with over 55 million acres cultivated worldwide in 2004. While the Bt crops have been effective in some cases, critics have pointed out that, among other possible health and environmental hazards, the pesticide no longer breaks down, but rather persists in the environment for months and can even be found in plant residues. This creates the opportunity for pests to develop resistance to the Bt genes, thus posing a serious danger for organic growers who rely heavily on Bt for controlling certain pests.

A recent study by researchers at Cornell University confirms the fears of organic growers and critic of genetic engineering alike. In a two-year controlled study the scientists discovered that genetically modified crops containing two insecticidal proteins in a single plant efficiently kill insects. But when crops engineered with just one of those toxins grow nearby, insects may more rapidly develop resistance to all the insect-killing plants. The study published in the Proceedings of the National Academy of Sciences on June 14th also points out that several insects have developed resistance to Bt toxins in the lab, and recently, cabbage loopers (a moth whose larvae feed on plants in the cabbage family) have shown resistance to Bt sprays in commercial greenhouses.
from:http://www.seedsofchange.com/enewsletter/issue_48/news.asp

[Igel]

1. Better to link to the actual source:

http://www.news.cornell.edu/stories/June05/Bt.kr.html

And, the title there, minus the seeds-of-change editorializing: "Insects develop resistance to engineered crops when single- and double-gene altered plants are in proximity, Cornell researchers say".

The research was done in a greenhouse. They bred moth strains: each insecticial protein produced by the plants had some moth strain resistant to it, but no moth strain was resistant to more than one insecticidal protein. This had a few effects: it made sure that insects resistant to one Bt strain were exposed to the other strains of Bt-bearing plants, and it made sure that the moths had access to mates that were also to Bt, whether to the same protein or to others.

They showed possibility: This could happen in nature, but it was almost guaranteed to happen in the greenhouse, if it was able to happen at all.

[Kraklen]

2. Do insects...

develop resistance to Bt when it's spread the old fashioned way, by crop dusters?

[mosquito]

3. Yes

One example, from Science magazine, can be found here:

http://intl.sciencemag.org/cgi/content/abstract/284/5416/965?rbfvrToken=933aaa015e6a02c8683b304c871e53b62d2268fd

All organisms will eventually develop resistance to a persistent high mortality factor -- or go extinct.