Crop & Food Research (now called Plant & Food Research) has lodged an application with the Environmental Risk Management Authority (ERMA) for approval to grow kale, cabbage and broccoli plants which have been modified to resist caterpillar pests.

Research Leader Dr Mary Christey has used molecular techniques to develop plants which produce proteins that have insecticidal activity. When susceptible insects ingest this protein, it is converted into a toxin which kills them.

The gene for producing these large, crystalline proteins was isolated from a bacterium called, Bacillus thuringiensis (Bt). The insecticidal proteins and the bacteria that make them have been used as natural pest control agents for more than 30 years. Now New Zealand scientists want to test the effectiveness of inserting the Bt gene into the species that need protection from the insects.

Caterpillars are one of the main brassica pests in New Zealand and although several chemical control methods are available, many of these are becoming less effective as the insect pests become resistant to them.

If approved by ERMA, the field tests will assess the potential of the technology to protect brassicas from caterpillar damage without using pesticides, Crop & Food says.

They do not intend to release the brassica crops on a commercial scale.