Insect warfare: NZIER report suggests Samurai wasps as solution to stink bugs

An NZIER report has made a case for introducing Samurai wasps to deal with brown marmorated stink bugs (BMSB), should they become established in New Zealand.

The Ministry for Primary Industries has introduced new measures against BMSB after turning away car-carrying ships that were discovered to be contaminated earlier this month.

The incident has highlighted how vulnerable the local economy is to the bug, which originates from Asia and which has established itself in United States and Europe.

The NZIER report, commissioned by the Samurai Wasp Steering group and funded by Horticulture NZ, MPI and a raft of other horticulture groups, said gross domestic product would fall by between $1.8 billion and $3.6b by 2038 if BMSB became established.

Over the same time frame, horticulture export value would fall by between $2b and $4.2b, the report said.

An incursion would reduce crop yields, increase costs and lower the export value for exports, the report said. At the same time, it would impact on employment, wages and result in a poorer standard of living, it said.

The Samurai wasp is one of several natural enemies of the brown marmorated stink bug. The female wasp destroys between 63 per cent and 85 per cent of BMSB eggs.

NZIER, in its report, said the introduction of Samurai wasp would be successful in reducing yield loss if BMSB became established. In addition, the need for pesticides would become lower.

"While there is some uncertainty around the precise magnitude of these losses, overall, our modelling demonstrates that the economic costs of BMSB would be much lower if a biological control agent (BCA) were approved and introduced into New Zealand to manage the spread of BMSB. The mitigating effects of a BCA are far greater than simply using more chemicals," the report said.

Horticulture New Zealand chief executive Mike Chapman said a BMSB incursion would affect multiple sectors simultaneously.

"This is currently the number one pest threatening horticulture and we are fully supportive of action at the border to keep it out, including the recent moves to prevent ships contaminated with brown marmorated stink bugs from unloading their cargoes in Auckland," Chapman said.

Horticulture NZ chief executive Mike Chapman. Picture/Supplied.

NZ Winegrowers biosecurity and emergency response manager Edwin Massey said BMSB is one of the wine industry's highest biosecurity risks.

When BMSB feeds on fruit and crops, the major impact is discolouration, which can make products unsuitable for sale to consumers.

"While BMSB is not a threat to human health, it does emit an unpleasant odour when crushed or disturbed, so is regarded as a public nuisance," it said.

BMSB can also infest domestic gardens, damaging fruit and crops there. The bugs tend to gather in homes in cold weather and are difficult – and smelly – to remove, it said.