The Brown Marmorated Stink Bug is a very long name for the greatest threat to New Zealand’s biosecurity as we know it.
The brown marmorated stink bug is formally known as Halyomorpha halys, while for those who have to deal with it every day it is simply abbreviated to the BMSB.
A huge amount of time and money is spent every year trying to intercept the bug: searching and turning back shipping containers, intercepting packages, ensuring constant vigilance at airports, and educating the public to enlist their own help in spotting suspicious critters.
If we want an idea of just how bad it might be if the BMSB established itself in New Zealand, we don’t need to use our imagination, because in a country about the same size as ours, on the other side of the world, the stink bug is running rampant.
First discovered in northern Italy in 2012, BMSB has become such a big issue that it is causing 100 percent crop losses in some orchards, with farmers walking off their land.
Halyomorpha halys comes from Asia where it is native to China, Japan, Korea and Taiwan. There, it is kept largely in check by a tiny parasitic species known as the Samurai wasp.
No bigger than an ant, the Samurai wasp lays its eggs inside the egg clusters of the BMSB, and after they hatch the young Samurai wasps feed on the young stink bugs.
The Samurai wasp is a highly effective biocontrol agent, so much so that when the BMSB establish in areas without the wasp, the population explodes.
In the United States, the first BSMB was discovered in Allentown, Pennsylvania in 1998. It had spread to 40 states by 2012, the year it was first discovered in Italy’s Modena region. With the population capable of increasing in size 125 times each year, it’s taken just a few years for the BMSB to reach plague proportions in the north of the country.
Across Italy, scientists are working on a number of solutions, from new traps, to sprays, to biocontrol, as well as trying to better understand how the stink bug and its natural predators interact.
Unlike New Zealand, where the Environmental Protection Agency has pre-approved the release of the Samurai Wasp in the event of a stink bug incursion, Italy’s laws prevent introduction of a foreign species, regardless of the proven benefit.
However, the Samurai Wasp has been found already in small numbers in the country, and additionally, a similar parasitoid wasp native to Italy has also been found predating on BMSB eggs, albeit less efficiently.
Developing a new arsenal against the BMSB
Professor Max Suckling, of Plant & Food Research, has just spent the Italian summer working with colleagues at the Edmund Mach Foundation in Trentino.
He has been field-testing new trap designs against the existing arsenal deployed against BMSB.
He has also been working on a sterile insect defence, in which thousands of male stink bugs are collected, dosed with gamma radiation to cause sterility and then released back into the wild.
By having vastly more sterile males in an area than fertile males, the chances of a female being able to reproduce are greatly reduced. This could be an ideal way to stem an early outbreak in New Zealand, where a very small female population could be overwhelmed by sterile mates.
Professor Suckling is in no doubt of the serious threat posed by the bugs.
“I would call this a super pest because of the scale of the damage.”
“It's partly because it has such a wide host range. Here in San Michela, we're seeing it in the forest. And it's attacking the fruits and the seeds,” says Max. “It will go through the summer attacking seed heads of grasses eaten, and then move on to the fruit as the fruit ripens. So here in the vineyards, we're starting to see it moving on the grapes.”
“But also, it's a hitchhiker. It spreads very, very quickly. And in a region like this, where you can hear the trains and you can see the cars and the trucks, just moving things around, the bugs are hopping on and hopping off.”
“The same thing will happen in New Zealand, it will move through the country quickly. Because it's human-assisted. We can't stop the bug jumping onto a car or truck and moving down the line. And if it's a female and she's able to lay eggs, she'll establish a new population very, very quickly,” says Max.
For Professor Suckling and his colleagues, particularly those based in New Zealand, this research is a race against time.
Each year the stink bugs are kept out of this country, is one more year that science has to find a solution, a better trap, a new technique - and to prevent the devastation being seen in Italy from taking place at home.