Genetically Engineered Crops May Threaten Beneficial Insects

August 31, 1998

(Reprinted with permission from: P A N U P S, Pesticide Action Network North America Updates Service )

To get an "at a glance" idea of the possible consequences of this observation, you can go to: Comment by PSRAST

Three recent studies point to troubling and unexpected effects of genetically engineered insect-resistant crops on beneficial insects. These studies highlight the need for testing of impacts on non-target species before genetically engineered crops are approved for widescale use.

Scientists from the Swiss Federal Research Station for Agroecology and Agriculture conducted two studies that looked at the effects of Bt toxin on green lacewing insects. In nature, these insects feed on the pest targeted by Bt corn, the European corn borer. Lacewings, which are known for their appetite for aphids and other soft bodied insects, play an important role in maintaining the equilibrium of insect populations. They are also important for organic farming pest control strategies.

**  In one study, recently published in the Journal of Environmental Entomology, researchers found that the mortality rate of lacewing larvae increased significantly after eating Bt-toxin similar to that found in genetically engineered corn produced by Novartis.

Green lacewing larvae fed with Bt-toxin from transgenic organisms showed a significantly higher rate of mortality (57%) than a control group of insects (30%). The larvae were fed purified Bt-toxin produced by genetically engineered E. coli bacteria. The bacteria produce toxin similar to that found in Novartis corn.

** An earlier study produced even more disturbing results -- demonstrating the potential indirect impacts of Bt crops on beneficial insects.

Researchers compared the mortality and developmental rate of two groups of lacewings -- one that had been fed European corn borers reared on engineered Bt corn and another reared on corn borers fed non-Bt corn (the control group). The experiments revealed that green lacewings fed corn borers that had eaten Bt corn had a higher death rate and delayed development compared to the control group.

More than 60% of the lacewings fed Bt-corn-reared corn borers died compared with fewer than 40% of the control group. The researchers suggest that the higher mortality is Rdirectly associated with [Bt}-related factors.S Among surviving lacewings, those feeding on Bt-corn-reared corn borers required an average of three more days to reach adulthood than the control group.

** In a third study, Scottish Crop Research Institute scientists found that ladybird beetles fed aphids reared on transgenic potatoes experienced reproductive problems and failed to live as long as ladybirds fed aphids from ordinary potatoes (the control group). The potatoes were engineered to produce insecticidal lectins -- proteins from the snowdrop plant that bind to the surface of insect cells causing them to clump and stop functioning.

The researchers found that egg production of female ladybirds fed transgenic-potato-reared aphids was reduced by more than one-third, compared with the control group. Nearly three times as many fertilized eggs from fed engineered-potato- reared aphids died before hatching compared with fertilized eggs from the control group. In addition, female ladybirds fed aphids from transgenic plants lived only half as long as females from the control group.

None of these studies have been extended to field situations so it is far from clear whether these laboratory results reflect what might happen outdoors. However, if field results show similar effects, wide-scale use of some transgenic plants could diminish populations of beneficial insects or render some herbicides useless to control weeds.

Comment by PSRAST

Bt (Bacillus thuringiensis) is a naturally occurring soil bacterium used as a biological pesticide that can be cloned and inserted into a crop plant. The plant then produces its own toxin in most if not all, parts of the plant.

RNew Evidence on Bt-Corn Disputes CompaniesU Claims of Safety,S Greenpeace press release, August 21, 1998.
The Gene Exchange, Summer 1998.

Contact:

Jane Rissler, Union of Concerned Scientists, 1616 P Street NW, Suite 310, Washington DC 20036.
Greenpeace, Genetic Engineering Campaign, 736 West End Avenue, #8D, New York, NY 10025; phone (212) 865-5645; (212) 865-4128; email charles.margulis@dialb.greenpeace.org.

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Comment by PSRAST on the Lacewing study

These laboratory studies indicate that the use of GE crops containg Bt toxin in their leaves may lead to an important reduction of these beneficial insects. If these findings correctly predict what would happen in a field situation, crops engineered to produce Bt toxin might lead to an increase of harmful insect populations. This might offset the pesticidal effect of the Bt toxin. The pesticide situation might even become worse than before because extermination of lacewings might upset the equilibrium between different insect populations.

Bt toxin is just one of several pesticidal agents that are now engineered into GE crops. Similar effects might be expected from other "interiorized" pesticides. Use of several different pesticidal crops in the same region might upset the ecology of insects in an unpredictable manner that might cause agricultural problems and ecological disturbances.

These results call for careful studies of potential complications from the release of insecticidal GE crops before these can be allowed to be used in agriculture. This one of several reasons why we demand a moratorium on the reslease of GE organisms.