Weta get a taste for grape vines

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.