Dialogue: Well-considered approach to swatting indiscriminate pest

By RUTH FRAMPTON*

It is extraordinary that a project that has literally not even got off the ground is being pre-judged and condemned by people purporting to represent the local community.

The Ministry of Agriculture and Forestry's plan to use a helicopter to spray targeted parts of West Auckland has been supported twice by resident surveys, applauded by environmental groups, ratified by the technical advisory group, and reviewed and endorsed by two independent experts from the United States and New Zealand.

The painted apple moth eradication project is being compared with the white-spotted tussock moth operation that took place six years ago in the East Auckland. There are marked differences.

The pest itself behaves differently.



Spraying can now be carried out with pinpoint accuracy thanks to global positioning systems technology.

The area to be sprayed is also different, and attitudes have changed. Waitakere residents are concerned, and rightly so, about their unique environment. It would be irresponsible and unacceptable to spray unnecessarily.

Despite reports to the contrary, most residents in the suburbs to be sprayed still support eradication. A survey of 600 residents in November and December found 73 per cent of respondents thought it very important or important to undertake eradication. Overall, 62 per cent strongly agreed or agreed with the proposed spraying.

The latest moth trap catches, which track the spread of male moths, show a marked drop in numbers. This means the pest is between generations - an optimum time to spray, because a good proportion of the population will be in the caterpillar stage.

From its first discovery, the ministry recognised how serious the impact of this pest could be. Eradication was a priority, supported by the early establishment of a technical advisory group.

The painted apple moth is a sporadic pest in its native Australia. In New Zealand, it threatens forestry and horticulture, as well as the natural environment.

The caterpillars are indiscriminate feeders. Though they prefer wattles and acacia trees, they also feed on three native species, kowhai, karaka, and mountain ribbonwood.

If the moth were to become widespread throughout New Zealand, the economic impact has been estimated to be at least $48 million over 20 years.

In 1996-97, Operation Evergreen used blanket spraying with a DC-6 aircraft to eradicate the white-spotted tussock moth in East Auckland.

Unlike the tussock moth, the female painted apple moth does not fly, and this limits its natural dispersal. This encouraged the ministry to adopt a conservative and responsible approach that would minimise disruption to the community without compromising the chances of eradication.

Last May, its approach was reviewed by an entomologist from the American Forest Service and an independent New Zealand biosecurity consultant. They found the strategy appropriate, and prospects for eradicating the insect still look good.

The forest industry and others have applauded the ministry's quick response to the recommendations. These included developing a plan for targeted aerial spraying as an option for future control.

Targeted aerial spraying is part of a much wider programme to eradicate the moth. Property-by-property surveys have been conducted every seven to eight weeks to find the pest. Infested vegetation is ground-sprayed with Decis (a synthetic pyrethroid insecticide) and monitored for signs of reinfestation. When sufficient supplies of the aerial insecticide, Foray 48B, are available, it will be used for ground spraying.

Restrictions have been introduced to prevent removal of garden waste from infested properties and neighbouring properties and parks. Free, safe disposal of waste is being offered to more than 20,000 West Auckland properties.

Live moth trapping started in December 2000. Now more than 600 traps cover West Auckland through to Mt Wellington. Research is still being done find a synthetic pheromone (a sex attractant) to replace live female moths used in traps.

In some hard-to-reach areas around the margins of the Whau River and its associated waterways, Traherne Island, the Waikumete Cemetery and Avondale Peninsula, ground-based controls have proved ineffective because of the terrain and the height of trees. These are the areas targeted for aerial spraying.

A BK-117 helicopter will be used.

In favourable weather, six to eight sprays should be adequate. One spray will take about seven hours.

The Foray 48B spray being used is a formulation of Btk, a naturally occurring soil bacterium. This was the formulation used in Operation Evergreen. Btk kills caterpillars, but does not harm animals or people.

There has been much hype about the health risks of Btk,and this has caused unnecessary concern. The Auckland District Health Board gave Btk a clean bill of health.

This supported an earlier study during Operation Evergreen, which found no evidence that residents exposed to the spray suffered harmful effects or chronic health problems.

The study did report minor respiratory irritations during the spraying and, because of this, an independent health monitoring and support programme has been established for the painted apple moth project.

A health register has been set up and everyone on the list will be contacted by a doctor before spraying starts. The ministry has arranged a free local consultation service involving doctors, practice nurses and environmental health specialists. Residents who think they may have been harmed by the spray can use this service.

Pest eradication operations are notoriously difficult, and there is no guarantee of success. The painted apple moth project is complex, involving three local authorities, government departments, research institutions, and hundreds of people who could be inconvenienced.

Aerial spraying is not an ideal solution but is necessary to protect our environmental, forestry and horticultural interests.

People with concerns about the programme can call the painted apple moth 0800 number, 0800 969696, or visit the MAF website.

* Dr Ruth Frampton heads the Ministry of Agriculture's painted apple moth eradication programme.

MAF