A number of car shipments were turned away at the border last month because they were infested with brown marmorated stink bugs (BMSB), which have spread across the globe from their original home in East Asia.

The bug is not currently in New Zealand, but MPI has been asking the public to keep an eye out for the distinctive insects, which are much larger than our native stink bugs. Biosecurity experts are worried about the impact they might have on both native plants and agricultural exports.

Dr David Teulon, director of Better Border Biosecurity, says the BMSB has more than a hundred host plants and it is a pest of many vegetables, fruits and field crops.

“The largest economic impacts from BMSB in New Zealand are estimated to be in kiwifruit, apple and pears, vegetables, wine, other fruit and plant seeds.”

Teulon says increased interception data is consistent with outbreak populations of the bugs in North America and Europe and especially from ports trading in goods (e.g. vehicles) to New Zealand, as well as the timing of northern hemisphere overwintering.

“While many overwintering adults die on their way from the northern hemisphere to New Zealand, a small proportion become mobile as the temperature increases across the Pacific on their way here. Alarmingly, the BMSB has now been reported as invading at least one southern hemisphere country, Chile.

“Increased interceptions may also be the result of greater inspections in New Zealand as the risk has become more apparent. The reason for the recent increases in interceptions from Japan is not fully understood.”

Teulon says vehicles, machinery and other cargo coming out of USA and Italy have had to undergo mandatory pre-export treatment with methyl bromide, sulfuryl fluoride or heat since 2015 and 2017 respectively, and this treatment is now being considered in Asia. Detector dogs have been trained to sniff out BMSB and are currently being used by MPI to find them on ships entering New Zealand waters and as they unload.

“Using a surrogate stink bug, work is underway to provide MPI with a full dataset on fumigants (methyl bromide and sulfuryl fluoride), heat, as well as the more environmentally friendly ethyl formate. Several studies have been instigated to examine whether biological characteristics, such as odour or sound can be used to detect BMSB on their way to New Zealand or at the border.”

Teulon says considerable research on trap and lure development for the bugs has been done in the USA, primarily for pest management purposes, and additional research, under contract to MPI, has been undertaken to develop fit-for-purpose trap/lure combinations for border use in New Zealand.

“The suitability of these traps for surveillance use was successfully trialled in Chile recently and the traps are being considered for New Zealand‘s response plan.”

Extensive research in North America and Europe indicates that the local predators and parasitoids are not effective against the bugs and evidence to date would suggest that this would be the same here. The most promising biological control agent for BMSB is Trissolcus japonicus, a parasitic wasp not found in New Zealand, and research has been undertaken to determine its risks to non-target species and to understand its potential distribution here.

Dr Glenn Aguilar, senior lecturer and environmental scientist at Unitec, says most interceptions occur at ports. He said as the bugs were discovered mostly in ships carrying cars being imported to New Zealand, the greatest risk would be to Auckland as it has the highest amount of imported cargo. This would be followed by other areas with the risk proportional to the amount of cargo being imported.

“The model for current climate conditions shows that most of the country is highly suitable for the bugs. Due to the high suitability of New Zealand and the ever-increasing arrival of this organism to our shores, there is a significant risk of it becoming established here.”

In the US, it took the BMSB around 14 years after initial establishment to become one of the most significant pests in recent history. Dr Michael Rostás, senior lecturer in entomology and chemical ecology at the Bio-Protection Research Centre based at Lincoln University, says if it were to become established in New Zealand, growers would have to drastically increase the use of broad-spectrum insecticides to prevent significant losses, which could lead to higher residue levels in fruit and vegetables and have detrimental effects on beneficial insects (predators, parasitic wasps, pollinators), leading to the outbreak of secondary pests (mites, aphids, scales).

“Most importantly, it would be a huge setback for sustainable pest management programmes and a serious threat for organic growers.”