August 31, 1998
Genetically Engineered Crops May Threaten Beneficial Insects
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
** 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
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.
* 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.
Sources: RNew Evidence on Bt-Corn Disputes CompaniesU Claims
of Safety,S Greenpeace press release, August 21, 1998. The
Gene Exchange, Summer 1998.
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 email@example.com.
Pesticide Action Network North America (PANNA)
49 Powell St., Suite 500, San Francisco, California 94102
Phone (415) 981-1771
Fax (415) 981-1991
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