Quick Dips

Triple Kill of
Devasting Invader

Researchers are pleased to see at least one parasite in the country tripling in numbers annually.

A great deal of hard work has gone into ensuring the successful establishment of parasitic insects that eat developing wasps in their cells. Three such insects have been released into New Zealand since 1979, and one is proving particularly successful.

"Studies at Pelorus Bridge in Marlborough indicate that the number of parasitoids is tripling annually, therefore the number of wasps killed annually is tripling," says Barry Donovan, of Donovan Scientific Insect Research.

Donovan is studying the impact of the insects on the wasp population.

During the last half-century, New Zealand has been invaded by two species of wasps, the German wasp and the common wasp. It's not just people who are under threat -- beehives and fruit and grapes are also targeted by wasps.

"These wasps are subjecting our small forms of native wildlife to enormously devastating predatory pressures against which they have no defences at all."

Donovan considers that if a variety of wasp enemies can be successfully introduced from different areas overseas, the wasps could come under much greater biological control pressure than anywhere in their home range.

Such introductions have their own risks. New insects must be quarantined before they can be released. This ensures that they are free not only of all enemies and diseases that might harm them, but also that they are free of organisms that might harm other beneficial organisms already in New Zealand.