Wētā Work: Burrowing into the behaviour of ground wētā

The project, funded by the New Zealand Wine Futures Fund (NZWFF), seeks to develop an environmentally and economically sustainable solution to the growing problem of ground wētā, Hemiandrus bilobatus, grazing tender foliage in spring.

"That's a real challenge," says Dr Jessica Vereijssen, a crop protection entomologist at Plant & Food Research, who is used to working with introduced pest species like the meadow spittle bug, a potential vector for Xyella fastidiosa. "With a lot of the horticultural pests we work with, the last option - if you can't find a solution - is always to spray them with a pesticide. With the wētā, we have to make sure it stays alive and that we don't affect it."

The three-year project will build on work already done by Lincoln University and Massey University, and on the existing management tool of wrapping plastic sleeves around vine trunks to deter wētā from accessing the shoots.

The plastic sleeves are costly to install and maintain, and they result in a significant waste management issue, so the new project will look at practical and environmentally sustainable alternatives, such as planting a crop between the vines, providing a sweet food source at budburst to disrupt the vine grazing. "We are trying to understand what the insect is after feed-wise at that time of the year, in the vines," says Jessica. "And whether we can change its behaviour, by luring it away, for example, from the vines and providing it with a more suitable habitat and more suitable feed."

Professors Mary Morgan-Richards and Steve Trewik of Massey University's Wildlife and Ecology Group, co-authors of Ecology and sysematics of the wine wētā and allied species, with description of four new Hemiandrus species, have already gained good insights into the natural behaviour of the wētā in some Awatere vineyards and will be an important part of the project team, says Jessica.

The new project, starting 1 July, will build on their learnings, in discussion with impacted growers and also Mana Whenua, perhaps learning how Māori interacted with wētā in traditional gardens. Like much of her work, it will require the enquiry and deductions of a detective, says Jessica. "I love that. Where do they go? Where do they sleep?"

Researchers will watch the wētā behaviour over budburst, then again in February, to see whether they clamber up vines at other times of the year. "It's a really simple question, but we don't know that. If they are always in the vines, is it possible they are providing a biological control of, say, mealybugs? If we lure it away, would it increase the mealybug problem in vineyard?... These are things we would like to find out, through talking to people and observations as well."

Jessica says it's important that any solution is practical and economically viable for growers to implement, while also protecting the interests of the insect.

The NZWFF is funded trough New Zealand Winegrowers levies and project managed by Bragato Research Institute (BRI). The wētā project has co-funding from Indevin, Pernod Ricard, Yealands and Hortus to support a Massey University PhD student.

BRI Project Manager Stephanie Flores says the proposal was a great fit for the Futures Fund, where the requirement was novelty. "Plant & Food Research is a key research partner, and we're excited to be working with Jessica for the first time," Stephanies says. "She brings experience working in various crops throughout New Zealand, as well as a fresh approach to wine research that brings together social science, ecology and financial sustainability."