Genetic riddle of 'scorpion' pesticide virus

A NEW, genetically engineered pesticide, strengthened with scorpion poison, has become contaminated during a controversial trial.

The experiment, in which the pesticide was sprayed on caterpillar-infested cabbages in a field in Oxfordshire, caused a furore earlier this year after objections over environmental risks.

The pesticide contains a virus that infects caterpillars, and genetic material from scorpions that releases a nerve poison. This weakens the grubs and stops them feeding, allowing the virus to work more quickly.

Now evidence has been found in the sprayed field indicating that the engineered virus has become contaminated by the wild version, leaving infected caterpillars dark, gooey and ruptured, while larvae infected with the engineered version are left intact.

David Bishop, director of the Oxford Institute of Virology and Environmental Biology, which is conducting the experiments, confirmed yesterday that in some of the tests the group of caterpillars that died had done so in a way that was not expected.

According to George McGavin, lecturer in zoology at Trinity College, Oxford, and assistant curator of entomology at the Oxford University Museum, parts of the trial have been abandoned because the stocks of engineered virus, with the scorpion gene in place, became contaminated with the wild version, Autographa californica. This makes it difficult for scientists to interpret the results.

Professor Bishop was reluctant to discuss ongoing work. He said the characteristics of the dead caterpillars suggested that they might have picked up a bacterial infection, rather than a viral infection, but said it was too early to be sure.

He confirmed that one batch of the engineered virus had been found to be contaminated with the wild type, but said this was not used in the experiments. He was satisfied with the results of this year's trial, and said early results were consistent with his expectations. Target and non-target species of caterpillar were sprayed with the engineered virus at two doses - either at a concentration that might be used in agriculture, or at a concentration 100 times as great.

At the lower dose, all the target caterpillars died and none of the non-target caterpillars. At the higher dose, all the target caterpillars died, and about 10 per cent of the non- target caterpillars. He hoped this would help to allay the fears of critics who voiced concern about the experiments earlier this year, claiming that the pesticide threatened species other than the caterpillars against which it is aimed.