Bt crops produce proteins that are toxic to certain insect pests.
Increasingly, Bt crop varieties are engineered to produce a number of Bt
toxins simultaneously to control target pests more efficiently, expand the
range of target pests, and slow down the development of resistance. It has
been a concern that Bt crops could pose an increased risk for non-target
organisms, since the individual proteins produced might interact with one
another.



Jörg Romeis and Michael Meissle conducted a systematic literature search of
all major databases in order to spot evidence of interactions between Bt
toxins that might cause unexpected damage to non-target organisms. They
checked approximately 2,300 literature references for relevant results and
identified 58 scientific publications with results from laboratory or field
trials. The laboratory studies were conducted with a total of 35 insect
species from 24 families and 11 orders. Field trials recording the
frequencies of insects chiefly in Br maize and Bt cotton were carried out in
5 and 7 countries, respectively.

The researchers did not find evidence in the literature that Bt toxins in
combination have a different action spectrum than the individual proteins.
They concluded that genetically engineered plants containing combined Bt
toxins are as safe for non-target organisms as plants with a single Bt
toxin.

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