Beware the devastating threat from brown marmorated stink bug

It's the little bug that could be a disaster for all our growing industries, devastating New Zealand fruit exports.

The brown marmorated stink bug (BMSB), originally from Asia, is regularly intercepted at the New Zealand border as it spreads worldwide.

Plant and food entomologist Dr Jim Walker said if BMSB established itself it would have "serious impacts on the way crops were grown".

At a recent conference on BMSB, Professor Claudio Ioriatti said in northern Italy growers had been forced to encase orchards in insect-proof netting after sprays failed to eradicate BMSB.

"One of the largest fruit-growing organisations in Italy estimated 150 million euro losses in one single year," he said.

He said the main issue was not that it feeds on plants, but how it feeds.

"All along the fruit season, it is injecting digestive enzymes into the fruit and that causes a deformation, discolouration and pitting of the fruit."

Their name is well-earned – they reek when squashed, which is of extra concern to the wine industry at harvest when fruit is crushed.

New Zealand Apples and Pears chief executive Alan Pollard said there were reports from the United States that when BMSB first arrived, horticultural producers lost 90 per cent of production.

"They have moved from spraying the crops twice a year to twice a week and they still lose 30 per cent of their production. So it is a phenomenal risk with catastrophic outcomes for the industry."

The bug also directly affects people living in urban areas because it seeks to spend winter in houses.

Ioriatti said in Italy it was destroying home vegetable gardens and taking up residence in homes.

"It is moving from the fields in a massive way to the buildings.

"You can find these bugs in your rooms, in your luggage is, in your kitchen."

The instinct to spend winter indoors makes summer the season most likely for a BMSB incursion into the southern hemisphere. They have made their way into boxes of Barbie dolls and running shoes sent to New Zealand.

One of the few weapons to partially control the bugs is the samurai wasp, which has already been approved to release if needed.

It's a natural predator of BMSB and attacks about 70 per cent of the eggs laid on leaves, but the wasp alone won't protect or prevent damage occurring to our crops.

Unlike northern Italy, most New Zealand orchards don't have hail netting in place, so millions of dollars would be needed for netting infrastructure.

Together with the loss in production, it could stop the spectacular expansion of the apple industry, currently planting one million new trees a year.

Pollard said New Zealand apples trade on the basis of having the lowest residues of any country in the world, particularly in Europe and North America.

"If we were forced to spray at the level that is required to eradicate the stink bug we simply wouldn't have access to those markets."

Sex pheromones have been a solution for other imported pest insects, but no sex pheromone has yet been found, to trap BMSB. However scientists have recorded a sound they make by vibrating surfaces.

It is hoped reproduction might be impeded if the sound is replicated throughout vineyards via trellis.

Should bugs slip through our borders, early detection is imperative, allowing time to breed up samurai wasp numbers and contain the affected area.

"The responsibility for bio-security relies with everyone in New Zealand, not just orchardists," Pollard said.

"The urban community has a significant role to play as well, so I would urge all those in towns and cities to check your gardens, have a look at your properties and if you see anything that you are uncertain about ring the 0800 number and MPI and will help you."

People are asked to capture a suspect bug and call MPI on 0800 80 99 66.

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