Kicking up a stink over another unwanted pest

PLANT KILLER: Myrtle rust on willow myrtle, an Australian species.
PLANT KILLER: Myrtle rust on willow myrtle, an Australian species.

Be prepared for an unwelcome visitor: it never knocks, has six skinny legs and stinks.

In the past 15 years, several dozen brown marmorated stink bugs have been intercepted at the New Zealand border, usually hailing from the United States, although the pest is native to China, Korea, Japan and Taiwan rather than the Americas.

At times the bug has multiplied into plague proportions in the US since its arrival in the mid-1990s.

STINKER: An adult brown marmorated stink bug, almost 2cm long.
STINKER: An adult brown marmorated stink bug, almost 2cm long.

In 2010 it caused $37 million damage to apple crops in Maryland, Virginia, West Virginia and Delaware and some peach growers lost their entire crop.

The bug is one of two potential pests keeping biosecurity managers awake at nights; the other is myrtle rust, a plant fungus which has rapidly spread from northern South America across to Queensland where it was first detected in 2010.

Both pests were highlighted at a recent conference in Wellington hosted by B3 Biosecurity, where US and Australian experts presented delegates with their latest findings.

Tracy Leskey, a research entomologist for the US Department of Agriculture, told the conference the brown marmorated stink bug was typical of invasive species.

"It doesn't have the natural enemies that it evolved with. And a lot of the insecticides labelled as excellent against native stink bugs didn't work as well as we'd hoped against the brown marmorated," she said.

The natural predator of the bug in China is a parasitoid wasp which attacks eggs, and plans are afoot to introduce it in the US.

Mark Seetin, director of regulatory and industry affairs for the US Apple Association, said that in the 40 years that he had been in the industry, he had never seen one insect pose such a big threat.

"Unlike a typical insect which focuses on a crop or a narrow range of crops, this bug eats virtually anything," Seetin said.

The bug feeds on more than 300 host plants, including citrus, pipfruit, stonefruit, berries and grapes, corn, honeysuckle and roses.

Mike Butcher, from Pipfruit NZ, said the bug was a big threat that would be at home in the New Zealand environment.

"It would find it absolutely ideal, it survives very hot summers and very cold winters. New Zealand would be a breeze for it - like going on holiday," he said.

Butcher said that despite all the best efforts at detection at the border, it was "logistically impossible" to examine all the containers coming into the country.

"It would be better if that was done before the containers came in. But most likely it will turn up in people's luggage, we believe that is the way it spread through the US," Butcher said.

Ed Massey, from New Zealand's Ministry for Primary Industries (MPI), said the stink bug was a more challenging pest to target than the Queensland fruit fly because there was no effective lure to attract the males at the important beginning period of the season.

MPI is starting a campaign this spring to target the pathways it expects the bugs to take. These include not only passengers' luggage, but also because they may arrive in mail, organisations such as Ebay are carrying advertisements warning people to check packages.

There was a heightened risk in winter as the bug sought shelter from the cold in containers, personal effects or even mail, he said.

While the stink bug is a potential threat to horticulture, myrtle rust chiefly menaces native plants. Pohutukawa, rata, ramarama, manuka and kanuka are all members of the myrtle family. Feijoas and eucalypts are also affected.

It damages leaves, stems and fruits, covering them in a yellow dust, and has been described by officials of Nursery and Garden Industry Australia as "probably the biggest threat to Australia's ecosystem". Ultimately it will kill a tree or shrub.

The rust easily attaches itself to clothing, raising fears that travellers returning from infected areas will bring spores of the fungus into New Zealand. There is no way to eradicate it.

Fortunately so far the rust appears to prefer humid climates like Queensland, and chances are against it spreading to affect honey-producing manuka or already under stress species like pohutukawa and rata.

Gordon Hosking, of Project Crimson, said the organisation had known of the disease for some years, and the Far North would seem the "logical" place for it to make a home.

"We should be more proactive; we could raise seedlings in Australia and test to see what impact the rust has on our plants.

"That should be MPI's responsibility," Hosking said.

The Dominion Post