Weta get a taste for grape vines

Marlborough Midweek - - YOUR LOCAL NEWS - CHRIS WOOTTON

Weta are known for their habits of lurk­ing in dark spa­ces - of­ten dis­cov­ered in sit­u­a­tions where you’d rather not. When pulling on your gum­boots for ex­am­ple, or if you’re seek­ing time-out in a long-drop.

Be­ing noc­tur­nal crea­tures this is un­der­stand­able. How­ever, weta are also rather harm­less. The fear that many peo­ple have for weta is tem­pered by a fas­ci­na­tion with th­ese iconic New Zealand in­sects.

Rel­a­tives of the cricket, grasshop­per and lo­cust fam­i­lies, there are more than 100 different species of weta in New Zealand. They live the length and breadth of the coun­try in a va­ri­ety of habi­tats.

Gi­ant weta, ground weta, tusked weta and cave weta are the main types found in New Zealand. Ground weta are not as well known as other types.

Their habits dif­fer from other weta as they live in a bur­row in the ground. They don’t have the heav­ily spined back legs of the tree weta and they don’t form so­cial group­ings or chirp like other weta.

Here in Marl­bor­ough in the early 2000s, a then lit­tle-known species of ground weta was dis­cov­ered, caus­ing sig­nif­i­cant dam­age to vine buds in the Awa­tere Val­ley.

This led to a de­cline in grape pro­duc­tion and caused big prob­lems for grape grow­ers.

Weta have al­ways been in the Awa­tere, but the in­tro­duc­tion of vine­yards to the area proved to the weta’s ad­van­tage - the pop­u­la­tion boomed as a re­sult. It’s likely that ir­ri­ga­tion of vines com­bined with a read­ily-avail­able food source worked to the in­sects’ ad­van­tage.

Th­ese weta were iden­ti­fied as He­man­drius sp. ‘promon­to­ri­ous’, only pre­vi­ously known from a site be­tween Mar­fells Beach and Cape Camp­bell. Be­cause of its rar­ity, this species was clas­si­fied with a ‘‘nat­u­rally un­com­mon’’ threat sta­tus.

A tra­di­tional re­sponse would have been to wipe out in­sect pests

‘‘The fear that many peo­ple have for weta is tem­pered by a fas­ci­na­tion with th­ese iconic in­sects.’’

us­ing heavy duty chem­i­cal bug sprays. But grow­ers wanted a safer and more en­vi­ron­men­tally friendly op­tion.

Grow­ers in Marl­bor­ough sought out al­ter­na­tive so­lu­tions. A lo­cal Awa­tere Weta Group was set up, in­clud­ing wine com­pa­nies and grow­ers, al­low­ing every­one to share in­for­ma­tion on the best way to con­trol weta in vine­yards.

Con­stel­la­tion Brands spon­sored a three-year PhD re­search project by a sci­en­tist to study the weta and de­ter­mine the best means of con­trol­ling them in vine­yards.

The study helped build a good deal of knowl­edge around this pre­vi­ously un­known in­sect and its predilec­tion for eat­ing grape vine buds.

The best so­lu­tion iden­ti­fied by the study was al­ready in use on many vine­yards. It wasn’t cheap but it was sim­ple. It is a much pre­ferred method com­pared to chem­i­cal spray­ing. Bands sta­pled around the trunks of vines and vine­yard posts were found to be the best means of lim­it­ing dam­age while at the same time pro­tect­ing the weta pop­u­la­tion.

The bands work sim­ply by mak­ing it more dif­fi­cult for weta to clam­ber up the vines or posts. Very much like the steel bands at­tached to power poles to stop pos­sums from climb­ing them.

The next step will be im­prov­ing the band so it’s longer-last­ing in the sun and also ‘‘grows’’ with the vine.

He­man­drius sp. ‘promon­to­ri­ous’ weta con­tinue to oc­cupy the Awa­tere. The con­trol mea­sures aren’t cheap to im­ple­ment but this en­vi­ron­men­tally friendly so­lu­tion helps pro­tect one small part of New Zealand’s spe­cial bio­di­ver­sity, while al­low­ing a lo­cal in­dus­try to flour­ish.

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