Dr. Beatrix Tappeser, Dr. Hartmut Meyer
German Working Group on Biodiversity Forum for Environment and Development
Severalplants are being genetically engineered to make them toxic to insect pests. Two recent pieces of research have shown negative effects of insect resistant plants on beneficial, non-target insects.
Onestrategy is to genetically engineer Bacillus thuringiensis endotoxin genes (Bt) into crops, for example to be toxic to larvae of lepidopterian pests. Larvae of the cornborer intoxicated by feeding onmaize containing Bt were found to be poisonous to lacewing flies. Lacewing flies are beneficial insects as they are predators of lepidoptera larvae and are important for reducing these parasites incrops.
In experiments done at the Swiss Research Station Zurich-Reckenholz, two out of three lacewing flies died when they were fed on the cornborer larvae which had eaten Bt maize. Even some larvae ofanother species (African cottonworm) which are not normally poisoned by Bt toxin but which had taken up the endotoxin were fatal to lacewing flies.
Another strategy to create insect resistance is tointegrate genes of protease inhibitors (PIs), which are small proteins that interfere with enzymes in the intestinal tracts of insects. These PIs have the potential to induce development disruption andincreased larval mortality in a large range of insects, not differentiating between pests and beneficial insects. As a result, bees and other pollinators can be exposed to PIs through pollen andnectar. Researchers at the National Institute for Agricultural Research in France (INRA) investigated the effects on honey bees. They fed elevated levels of PIs together with a sugar solution to bees forthree months and found that such bees died 15 days earlier than bees fed normal sugar. Another effect was that after only 15 days of ingesting PIs, bees had problems to distinguish between the smells...