Wasp warrior on hand
The Environmental Protection Authority (EPA) has recently approved the use of a pest in case of brown marmorated stink bug (BMSB) incursion. Meet the Samurai wasp.
BMSB is one of the biggest biosecurity risks facing New Zealand and is frequently intercepted at the border. It feeds on over 300 plant species, many of which are important horticultural crops, and may feed on New Zealand native plant species as well. It can reproduce to high population numbers rapidly, destroy crops and gardens, and get into homes to cause significant social nuisance.
Industry and Government have recognised that it is vital to prepare to fight BMSB if it does arrive. Thankfully, is has a nemesis, the Samurai wasp. It’s tiny, about the size of a poppy seed, but a natural enemy of BMSB. The female wasp lays her eggs inside those of the stink bug, killing the larvae in the process. Studies overseas have shown that the wasp can destroy over 70 percent of the eggs in a stink bug egg mass. Samurai doesn’t sting and is completely harmless to humans and animals except stink bugs- great news for us, bad news for BMSB.
It is expected that once released, the Samurai wasp will establish a self-sustaining population on BMSB, keeping population numbers down, but not exhibiting total control. It will instead become one of a range of tools used to manage BMSB, and would likely help to reduce the amount of insecticide needed to control the pest.
Parasitoids like the Samurai wasp can locate and target BMSB eggs, and would maximise the chance of controlling any outliers during a biosecurity response - think of them as BMSB-seeking missiles. In a longer-term situation, such as if BMSB cannot be eradicated and becomes established, the wasp will likely become a key tool in keeping BMSB population levels down, as well as providing an alternative to increasing use of sprays.
Unlike many of the biocontrols that are currently used in NZ the Samurai wasp will not be available to the general public. Permission to release the wasp will be subject to a number of strict controls that will dictate when, where, and by whom it can be released. Only the Ministry for Primary Industries (MPI) and its appointed agents can use it and the Samurai wasp may only be released after a BMSB incursion has been detected, and only at the site of the incursion. Alan Pollard, chair of the brown marmorated stink bug council said he's pleased with the EPA announcement but believes there is a long way to go.
“The approval of Samurai as a biocontrol is an excellent step, and the first milestone on a long journey,” he said. “We’ve seen overseas growers rely on high levels of insecticide as the primary control for BMSB and, while this wasp provides the opportunity to reduce our dependence on chemicals, a full response will require every weapon in our armoury, the Samurai wasp is not a silver bullet.
“A NZ Institure of Economic Research report, commissioned by the Samurai Wasp Steering Group, has estimated that gross domestic product would fall by between $1.8 billion and $3.6b in just 20 years if BMSB became established. It also estimated the horticulture export value alone could fall by over $4b, and this is an unacceptable risk to our economy.
“This is a significant step towards preparing for a major biosecurity risk that threatens communities across NZ, and we’re very pleased to be one step closer to having another tool in our toolbox. The next task is to look at where we can source sufficient populations of the Samurai wasp, and to seek permission to import the wasp if we need to use it.”
The application for the Samurai wasp was made possible through the collaboration of horticultural industry groups and the MPI, working together under the Government Industry Agreement for Biosecurity Readiness and Response (GIA). The application was informed by critical impartial research undertaken by the science community and was supported by public submissions from many growers.
Readiness efforts continue so the country can be ready if and when BMSB invades.