Sep. 25, 2006 Scientists at Rothamsted Research have identified how aphid parasitic wasps prevent their offspring being eaten by ladybirds. The tiny wasps implant their offspring parasitically into aphid pests, but should the aphid get eaten by a ladybird, the growing wasp would be consumed as well. The researchers, supported by the Biotechnology and Biological Sciences Research Council (BBSRC), have found that to protect their offspring, adult wasps have evolved to avoid the smell of a short-lived blend of chemicals that ladybirds deposit with each footprint they make. The scientists have identified the particular cocktail of chemicals.
Both wasps and ladybirds are predators of aphids but they have evolved techniques to enable them avoid each other and maximise their own success. As aphids are significant pests for gardeners and farmers the natural mechanisms that have developed help these two predators to interact efficiently to help control aphid numbers.
The scientists at Rothamsted Research, Professor Wilf Powell and Dr Mike Birkett, together with visiting Japanese scientist Dr Yoshitaka Nakashima, have identified the chemicals involved and have also shown that the smell of different ladybird species repels different parasitic wasp species to various degrees. Dr Wilf Powell explained: "We found that parasitic wasps attacking aphids living in a wooded area responded most strongly to the chemical footprints of woodland-dwelling ladybirds and similarly for those found more often in fields of crops. This suggests that these two aphid predators have evolved mutually beneficial avoidance techniques to maximise their own chances of success.
"A better understanding of the natural interactions between parasitic wasps, insect predators and their prey has the potential to help us to use them more effectively to control garden and agricultural pests and reduce the amount of pesticides we spray."
The research is being displayed to the public for the first time at an open weekend at Rothamsted Research next weekend (30 September-1 October). The Rothamsted scientists worked in collaboration with a visiting researcher from the University of Agriculture and Veterinary Medicine, Obihoro, Japan who was supported by the Japanese Society for the Promotion of Science. Some aspects of the work were also supported by the Department for Food, Environment and Rural Affairs (Defra).
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