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.

The Orchardist - - Biosecurity - By Leanne Ste­wart

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.

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