MAF gives up trying to eradicate gum leaf moth

3.00pm

Ministry of Agriculture and Forestry officials say they have given up on trying to eradicate the gum leaf skeletoniser moth in Auckland.

The voracious moth is a potential threat to tens of thousands of plantation eucalypts grown for high quality paper production, and a lot of gum trees in urban plantings and parks.

MAF has been battling the Australian pest since it was discovered at Mt Maunganui in June 1997, and thought it had won the battle, until the pest popped up at Auckland in 2001.

MAF's national manager of forest health, Ross Morgan, said in March the government had retained eradication as a "possible goal" but was trying to work out whether eradication was either feasible or affordable.

But today, MAF's director of forest biosecurity, Peter Thomson said the moth has been detected across approximately 25,000 hectares of Auckland, from Devonport to the north, to Wiri and Auckland Airport in the south, and the government would only try to manage the problem.

The moth's caterpillars munch leaves on many eucalypt species -- leaving just a skeleton -- and can slow tree growth or kill young trees.

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

It was later also found at nearby Waitui Reserve and Omanu golf course.

Forestry health officers spent several weeks checking around 800 eucalypts within a 2km radius of the Mt Maunganui Golf Course, the centre of the infestation. The trees were surveyed on more than 300 private and commercial properties, as well as the golf courses, parks and reserves. The Government spent only $20,000 a year on its initial programme to stamp out the skeletoniser at the Mount -- which was based on spraying neighbouring eucalypts within 20m of an infested tree.

But in 2001, the skeletoniser was also discovered in Waikaraka Cemetery at Onehunga in Auckland.

It spread to Manukau Memorial Gardens, Mangere, Otahuhu and the Auckland International Airport and nine other known sites around Auckland, and MAF began a "delimiting survey" with a 100km radius from the known infestations to check exactly how far the moth has spread.

"We have now determined that eradication is not an option owing largely to the extent of the current infestation and the likely rate of spread of the pest," Mr Thomson said today.

Unlike the painted apple moth, the gum leaf skeletoniser female moth can fly up to 2km and lay eggs in several locations.

He said a group of industry and technical experts had said eradication would require a combination of widespread removal of host trees and aerial spraying for a period of two years.

But the chances of successfully eradicating the pest were considered to be low and long-term management was seen as a "more realistic option".

As an alternative to eradication, MAF would consider options for assisting commercial growers, councils and other stakeholders in the transition to long term management of gum leaf skeletoniser. This might include trying to slow the moth's spread, research into biological control agents and research into effective control measures such as spraying options for commercial plantations.

MAF has been also field testing a new pheromone developed by Hortresearch scientists who previously put together a pheromone, or sexual scent, to attract the male painted apple moth to population-survey traps.

With the help of John Bain at Forest Research, the pheromone which attracts skeletoniser males to mating was extracted from female moths and the chemical components identified. Male gum leaf skeletoniser moths have been caught in Queensland in traps baited with the synthetic pheromone.

- NZPA