A tiny hairy caterpillar that can strip a mature tree of its leaves in 90 days has been declared Public Enemy Number One by the New Zealand government.
The government is next month to start mass aerial spraying of its largest city, Auckland, in a last ditch attempt to wipe it out.
Up to 64 000 homes and about 250 000 people could be blitzed with a biological insecticide in what has been described as the biggest pest eradication campaign over an urban area ever in the developed world.
Some areas could be sprayed 40 times during the three-year campaign – and the government admits that even then there is no guarantee of getting rid of the painted apple moth (Teia anartoides), which arrived in Auckland from its native Australia, probably in a shipping container, in early 1999.
The female does not fly, but is impressively fecund, laying up to 700 eggs at a time and producing several generations of caterpillars each year that are distributed by the wind and feed voraciously on a wide range of greenery.
They have taken a liking to 40% of all trees in Auckland’s parks and gardens and conservationists say they threaten prized New Zealand natives like kowhai and karaka and could do significant damage to the indigenous ecosystem.
But what prompted the government into an eradication programme that is drastic and expensive — at 111,6-million New Zealand dollars (about 51-million US dollars) — is the threat to the economy.
New Zealand has some of the world’s biggest planted pine forests and the painted apple moth finds them to its taste, as well as the apple, pear, cherry and apricot trees that account for a big part of the country’s horticultural exports.
A preliminary campaign of aerial spraying which began in January has failed to get rid of the moth and Treasury accountants advised the government against spending more money.
But although experts said there was only a 60-80% chance of eradication, Agriculture Minister Jim Sutton said the potential benefits outweighed the risk of doing nothing more.
The initial campaign, using helicopters spraying an insecticide, Foray 48B, based on a naturally occurring bacteria known as Bacillus thuringiensis kurstaki (Btk), saw 600 hectares of West Auckland sprayed eight times.
This was started when up to 900 moths a week were being caught in baited traps around the city, a year after the Ministry of Agriculture and Forestry’s campaign leader — who has since resigned — said she was ”cautiously optimistic” it had been eradicated by ground-based spraying.
The government has now approved a major extension of the spraying area to 8 000 hectares, with another 4 000 hectares to be targeted if new infestations of the moth are found.
The campaign has already been highly controversial, with residents complaining that spraying of their houses from helicopters 45 metres above the ground had affected their health.
Helen Wiseman-Dare, of an organisation called West Aucklanders Against Aerial Spraying, said nowhere in the world had people been sprayed with Foray 48B as extensively as they have in Auckland and its long term safety was not proved.
She said more than 700 reports of adverse health effects had been documented as a result of using the spray to eradicate a similar Australian pest, the white spotted tussock moth, in another part of Auckland between 1996 and 1998.
The government insists the spray, which kills the caterpillars by rupturing their gut after being ingested, has been used in the United States for 20 years with no ill-effects to humans.
It will use two fixed-wing aircraft and a helicopter in the extended blitz to start next month. – Sapa-DPA