Australian researchers are developing a new sort of pesticide which "strangles" insects by preventing them from shedding their shells as they grow.

They say it will be more environmentally friendly than chemicals, because turns molecules in the pests' hormones against themselves and so will not affect other organisms.

The research team is based at CSIRO, the Commonwealth Scientific and Industrial Research Organisation.

Flu clue

The project leader, Dr Paul Savage, says it used a totally new approach, similar to that used for the development of the 'flu drug Relenza.

"CSIRO looked at the molecular structure of the 'flu virus to find a way to block it from working and thus create the 'flu drug. We're now looking at using the same technique to beat insect pests."

Dr Savage believes the project's success could open a new era for insect control. The Australian Government has given it a grant of $A1 million.

Trapped

The research is based on an insect hormone, ecdysone, that regulates the moulting process. Insects need to moult at different points during their life cycle, as their shells or carapaces cannot grow to accommodate their growing bodies.

When the researchers have determined the structure of the receptors for the hormone in particular pests, they will be able to design molecules to prevent it working.

So the insect, unable to moult and trapped inside its inflexible shell, will die.

Insects must moult or die

Dr Savage said: "Because the structure of the receptors varies from one species to another, the new agents can be targeted on specific pests such as flies or plant-sucking bugs."

"This will have considerable safety and environmental benefits, because the new products will not affect anything other than the target insects. Humans, mammals, birds and most other insect groups will not be affected."

Another advantage is that the new pesticides will be effective at lower doses. The process of developing and registering them should also be quicker.

And Dr Savage believes that, although pests eventually develop resistance to chemical pesticides, they are less likely to be able to do so now.

Export earnings

"It will be very difficult for insects to develop a resistance to these new agents, as the target site is fundamental to their life cycle."

Some existing pesticides enjoy sales of more than $A100 m annually, and the markets for both crop and animal protection are worth billions.

Dr Savage believes the team's work should bring in substantial foreign earnings.