An overview of Bt crops

What are Bt crops?

"Bt", or bacillus thuringiensis, is naturally occurring bacterium that is found in soil and works as an insecticide. Using the proteins in Bt, scientists developed a gene in corn and potatoes that triggers the production of the Bt protein within those plants. The result is that these modified plants produce this Bt protein, which enables the plant itself to resist insect pests.

Are Bt crops safe?

All Bt plants commercially available in Canada have been thoroughly assessed for food use, livestock feed, and unconfined environmental release. The CFIA does environmental release and feed assessments, and Health Canada does food assessments. Examples of the factors used in livestock feed and environmental release assessments can be found on the CFIA Web site in the decision documents for plants with novel traits.

The history of use and extensive literature indicate that Bt proteins should not pose a risk to humans, other mammals, fish, birds, and most insects.

Why do farmers use Bt corn?

Farmers use Bt corn for the same reason they use any pest management tool—to grow better crops to make their farms run more efficiently. Some farmers, including those who prefer to use organic agricultural practises, spray Bt on their crops. In some situations, insecticides produced inside a plant, as with Bt corn, may work better than topically-applied insecticides, so some farmers choose this method of insect control.

Can insects develop resistance to Bt?

Over time, insects can become resistant to any insecticide, so scientists have long been interested in insects developing resistance to Bt. This interest now includes crops expressing Bt. For this reason, the CFIA has mandated insect resistance management plans (IRM plans) suited for the biology of each target insect pest. The IRM plan is an agreed upon, common plan that developers are required to implement.

For example, for the European corn borer, the Canadian Corn Pest Coalition (CCPC) developed the standard IRM plan, and this was adopted by the CFIA as a regulatory requirement. The U.S. Environmental Protection Agency later adopted the same requirement. More information about the Coalition and its activities—including the roles of farmers and developers with respect to IRM plans—can be found on the CCPC Web site.

What about Bt and soil health?

The health of soil can be an indicator of the overall health of the environment. Scientists can determine how healthy a soil is by examining its flora and fauna and by observing and measuring its physical and chemical conditions.

While Bt crops can release Bt proteins into soil, it is known that soil organisms are already exposed to Bt proteins that originate from the naturally occurring Bt bacteria, which are present in soil, or as a result of Bt being applied as an insecticide. For many years, Bt insecticides have been used without reported negative effects on soil health. Many published scientific papers show that Bt proteins do not significantly affect earthworms or other small invertebrates.