Country Life: Harnessing the power of plants to combat vineyard threats
Photo:
Craig Robertson
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Are some grapevines better at naturally defending themselves from a disease-spreading pest which costs the New Zealand wine industry millions of dollars?
Michelle Thompson is running trials at Plant & Food Research in Lincoln to find out.
The PhD student is studying the feeding behaviour of mealybugs, tiny insects which extract sap from plants, reducing the plants' vigour and production.
She wants to identify grapevine varieties which produce higher levels of defence compounds that deter the insects.
Mealybug electropenetrography on grape leaves
Photo:
Craig Robertson
Conventional vineyard practice at the moment is to use chemical insecticides, as well as removing infected plants.
"It would be great to have a more natural way of managing mealybugs and protecting our vineyards, something that's more environmentally sustainable and also less costly," Thompson told
Country Life
.
Leafroll virus damage in a Hawkes Bay vineyard
Photo:
Tony Corbett
Leafroll virus
Photo:
Tony Corbett
"I'm working with Citrophilus mealybugs and they are able to feed on lots of different parts of grapevines - the trunks, canes, leaves, berries and the roots."
Mealybugs also transmit the Grapevine Leaf Roll Associated Virus.
"This impacts the health of the vine, reduces yields and it changes the grape quality as well."
Mealybug electropenetrography on grape leaves
Photo:
Craig Robertson
In the lab, Thompson is using a technique called electropenetrography to study how the pests feed.
She is working with four grapevines inside two metal cages, designed to minimise external electrical interference. The vines have differing levels of bioactive compounds in their leaves
.
Mealybug electropenetrography on grape leaves
Photo:
Craig Robertson
The mealybug electropenetrography on grape leaves is conducted in faraday cages
Photo:
Craig Robertson
"There is a plant electrode that's inserted into the potting mix of the vines and a tiny voltage is applied to the plants."
A mealybug attached to an electrode is placed on the leaf of each plant. The gold conductive wire glued onto their back is light enough not to restrict their movement.
Michelle brushes the dust off a mealybug before attaching the conductive wire
Photo:
Craig Robertson
Michelle uses a microscope to attach the wire to the mealybug
Photo:
Craig Robertson
A Mealybug moves along a grape leaf while attached to the wire
Photo:
Craig Robertson
The technology measures electrical signals produced by insects feeding on the leaves and monitors their feeding behaviour.
"I want this information on mealybug feeding behaviour to be able to inform breeding of rootstock varieties, so we can breed varieties that are resistant to mealybug feeding and therefore reduce virus transmission in our vineyards."
The project, Smart Adaptive Rootstocks for a Changing World, is funded by the Ministry of Business, Innovation and Employment's Endeavour Fund.
Mealybug electropenetrography on grape leaves
Photo:
Craig Robertson
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