Genetically modified plants may still need pesticides
Andy Coghlan and Barry Fox From New Scientist, 18 December 1999
Keep that spray
Crops made resistant to pests still do better with
FARMERS may need to douse their fields with yet more pesticides to get the best
out of genetically modified plants. At least, that's the implication of patent
applications filed by Novartis of Basle in Switzerland, one of the leading companies
in the field.
The applications (WO 99/35910 and WO 99/35913) were filed after scientists at
Novartis realised that a wide spectrum of insect pests was attacking Bt maize, its
major GM crop. Genes inserted into the maize enable it to make the Bt toxin, a
bacterial protein that kills European corn borer larvae. These larvae chew their way
into the stems of young maize plants and can kill them before they get established.
But many GM plants that saw off the borer larvae were later attacked by
sap-sucking insects. "Bt toxin has a rather narrow spectrum of activity, so you don't
get control of all pests," says Walter Smolders, head of patents at Novartis Seeds.
To find a way round the problem, Novartis scientists tried applying different
combinations of the company's pesticides to the Bt maize. Their patents identify
combinations of pesticides that could raise yields of the maize by 20 per cent.
The same pesticides appear to increase the yields of other GM plants, including
those engineered to resist the effects of herbicides. So Novartis has extended its
patents to cover use of the pesticides on a long list of transgenic crops including
maize, cereals, soya beans, potatoes, rice, cotton and mustard. If the patents are
granted, this means they will also apply to crops from competitors such as
Monsanto of St Louis, Missouri.
Heinz Hammann, head of patents in Novartis's crop protection division, claims the
pesticides mentioned in the patents are mostly environmentally benign, killing only
the pests which attack the plants. Maize, for example, is vulnerable to sapsuckers
such as the flea beetle (Phyllotreta agriotes) and various aphids. "Non-target
species don't suck the plants, so they're not harmed," he says.
But some of the pesticides are less friendly. Carbamates, for example, act on the
nervous system of pests and are known to affect birds, fish, game, bees,
mammals and other farmland wildlife. And given that agribiotech firms have
consistently argued that GM crops will reduce pesticide use, Novartis's patent
applications are sure to be seized upon by groups that oppose the technology.
Brian Johnson, head of the biotechnology advisory unit at English Nature, a
conservation watchdog, says he wants to see evidence confirming Novartis's
suggestion that the use of pesticides on GM crops outlined in its patent applications
will be less environmentally damaging than conventional chemical treatment of
ordinary maize. "It's the impact of the whole process on biodiversity that counts,"
he says. "But the impacts of what they are proposing are not known."
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