New research uses mussel shells to control grass grubs in vineyards
Mussel shells are already used to control weeds in vineyards and now may be able to repel destructive grass grubs too, new Lincoln University research suggests.
Using greenshell mussel in vineyards, although not a new practice, could be seen as a win for the aquaculture and wine industries, the study said.
Empty mussel shells found around the region, like at "Shell Mountain" near Havelock, could be used to deter grass grubs.
That's effectively a summary of the work by Mauricio Gonzalez-Chang, a Lincoln University PhD student whose work in Marlborough using greenshell mussels to control grass grub is being seen as a win-win for the aquaculture and wine industries.
Speaking from his home in Valdivia in southern Chile, Mauricio laments the fact that his own nation's wine industry is showing much less interest in his work than New Zealand's. He is currently looking for more research or a wine industry position to continue his work.
Grass grubs emerge from the ground in spring and can cause considerable damage to vines in a two-to-three hour feeding frenzy before they drop to the ground, mate and carry eggs into the soil, which develop as larvae.
"It's a huge problem among wine growers, especially if they are organic.
"We know New Zealand wants to keep its reputation for being clean and green and producing high-quality wine," he said.
Sustainable winemaker Kono Beverages was keen to get on board with the study, offering up its Awatere Valley Tohu block for Gonzalez-Chang to trial several variables to control grass grubs, including clay particles.
"One day I was walking into the vineyard and one of the workers said they were using mussel shells to control weeds," he said.
He set up a trial testing to see if mussel shells spread under vines had any impact on the insects.
From his results, he believed the light reflected from the shells disoriented the flying grubs, making them land elsewhere than on vines, which have mussel shell beds. They also provided a barrier to any beetles that did land on the ground.
During his presentation at last year's Romeo Bragato viticulturists conference in Blenheim, Gonzalez-Chang showed a video clip of how the use of mussel shells reduced grass grub damage to vines by 75 per cent.
Marine Farming Association president and winegrower Jonathan Large said both industries would benefit if mussel shells were more widely used.
"Everyone has seen the shell mountain near Havelock," Large said.
"We are looking at options such as return to the sea but if the shells help control grass grub, I for one am interested in putting them on my vineyard."
*An earlier version of this story incorrectly attributed quotes from Jonathan Large to Lincoln University PhD student Mauricio Gonzalez-Chang.