PLANT breeders who want to produce crops more resistant to insect pests should spare a thought for the needs of our insect 'friends' - the carnivorous insects that prey on the pests. Two American ecologists have shown that a simple change in the architecture of a plant can dramatically tip the balance in favour of the predators and against the pests (Nature, vol 345, p 433).
Peter Kareiva and Robert Sahakian, of the University of Washington at Seattle, studied the triangular relationship between pea plants, aphids and ladybirds. They found that ladybirds were much more efficient when they hunted aphids infesting leafless pea plants, rather than the normal variety.
The explanation is simple. From a ladybird's point of view, the trouble with leaves is that they are slippery - stems and tendrils provide a more secure footing. The scientists found that ladybirds fall off the normal variety nearly twice as ...
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