Invading Aussie pest may be threat to rata, kanuka

An environmental lobbyist says the gumleaf skeletoniser moth - which the Government has decided not to eradicate - may prove to be a pest on native forests of rata and kanuka.

The Ministry of Agriculture and Forestry said it had abandoned the option of eradicating the skeletoniser and was adopting a "long-term management" approach to controlling the pest.

Forest and Bird biosecurity spokesman Geoff Keey said the lobby asked MAF to carry out "host testing", which had shown the Australian pest would eat some native trees as well as eucalypts.

Feeding trials in which eggs and caterpillars were placed on plants that might be vulnerable to browsing by the pest showed that southern rata and kanuka were the native species most at risk.

In the experiments, few caterpillars survived after being hatched on native plants, but more survived when transferred on to native plants when larger.

Forest and Bird said this suggested that the main risk lay in caterpillars spreading from neighbouring eucalyptus trees to natives.

The biggest danger to native trees was from skeletoniser outbreaks in eucalypt shelterbelts or forests, which then spread to nearby native forests of rata or kanuka.

"'It will be important to establish buffer zones around areas of rata or kanuka forest where eucalypts cannot be grown," Mr Keey said.

It would also be important to keep the pest out of the South Island.

Forest and Bird wants Biosecurity Minister Jim Sutton to investigate how the incursion of gumleaf skeletoniser moths was allowed to spread to the point where eradication was declared impossible.

"The Ministry of Agriculture and Forestry should have been on top of the problem long before it spread to 25,000ha in Auckland," Mr Keey said.

The moth was first discovered in a dozen gum trees at Mt Maunganui golf course in June 1997, apparently after hitching a ride into the country in a golf bag.

In 2001 it was found in Waikaraka Cemetery at Onehunga, in Auckland, and it has since spread to more than 25,000ha.

- NZPA