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[BEIJING] Chinese scientists have developed a way to protect crops using wasps that deliver lethal viruses to insect pests.

The technique, developed at the Wuhan Virus Research Institute won second prize at the 2005 National Technological Invention Awards, which were presented at the National Science and Technology Congress in Beijing on Monday (9 January).

Lead researcher Peng Huiyin says the approach costs 25-40 per cent less than chemical pesticides and is more environmentally friendly. It can control more than 20 insect pests, mainly caterpillars, he adds.

Both viruses and parasitic wasps have been used to kill pests before, but the Chinese scientists are the first to combine the tactics, says co-researcher Zhang Lin.

Certain parasitic wasps lay their eggs in those of other insects. The wasp larvae feed there, killing their hosts before hatching.

The researchers took parasitised insect eggs and soaked them in a solution containing a virus that is lethal to the pest, but harmless to the wasp. When the wasps' offspring hatched, the virus became attached to their bodies.

The idea was to exploit the fact that females often crawl over hundreds of pest eggs before selecting one to lay their egg in.

"This way the virus can be spread to hundreds of pest eggs," Zhang told SciDev.Net.

After hatching, any pest larvae that have not been parasitised feed on the remains of their eggs and ingest the lethal virus.

Zhang says that during 15 years of research, the team has identified more than 20 viruses that kill different pests but not the wasp.

Field trials of the methods have been conducted on more than 13,000 hectares of farmland in China. "It is very likely to be commercialised within one or two years," says Zhang.

Farmers using the method would put virus-coated pest eggs that contain developing wasps in their fields and wait for the wasps to emerge. Depending on which pest was a problem, wasps could be tailored to carry a different virus.

The researchers have published most of their findings to date in the journal Virus Research, with their most recent paper appearing in last month's edition.

So far, there is no evidence that the pest species have developed resistance to the viruses, says Zhang.

Reference:
Virus Research 114, 80 (2005)

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