Mauricio González-Chang, a Lincoln University PhD student in the Bio-Protection Research Centre, presented evidence that mineral feeding deterrents and mussel shell mulch can protect vines from grass grub beetle attack.

His study of vines in the Awatere Valley in Marlborough, found that natural silica-containing feeding deterrents, such as kaolin particles (hydrophobic particle films) and diatomaceous earth, reduced the damage caused by beetles by about a third in chardonnay, and a half in pinot noir grape varieties.

While the silica results were promising, the greatest reduction in damage was seen when crushed mussel shells were spread under the vine rows. The shells affected landing behaviour of the beetles and resulted in a two-thirds reduction in feeding damage.

Grass grubs have been damaging pastures in New Zealand for more than 100 years, and the adult beetles are a severe pest of grape vines. The beetles emerge in spring and feed on the vine leaves, shoots and buds. Damage has been reported in vineyards from Waikato to Waipara. As well as vines, the beetles can also feed on other horticultural crops, such as kiwifruit, avocados, tamarillos, apples and blueberries.

While insect numbers can be controlled with synthetic pesticides, consumers increasingly want to reduce or eliminate their use. “We know that wine growers in New Zealand have a respect for their environment, and want to keep the nation’s reputation as a clean, green country producing high quality wine,” González-Chang says. To do this, more research is needed into alternative pest control methods that are practical, inexpensive and sustainable.

The Chilean student was inspired by the diversity of speakers at the Romeo Bragato conference. “It was an amazing experience to meet all kinds of people there, from growers and winemakers to scientists and politicians, all working together for a better wine industry, but also committed to protecting the environment, and enhancing social benefits for their workers.”

The knowledge that his work should benefit New Zealand wine growers was one of the González-Chang’s key motivations for undertaking the study, which was supported by Callaghan Innovation and leading sustainable winemaker Kono Beverages. “However, we still have many questions to answer about how these treatments are working, and whether preventing feeding in one area will increase damage in another.”

He is currently seeking funding to continue his research in the Marlborough vineyard for another season.

Watch the beetles feeding at night with and without mussel shell mulch: http://bit.ly/2cLWbLm