Could the extended use of single row drape nets in the vineyard limit fruit exposure to the damaging effects of climate extremes?
According to a demonstration trial recently conducted by the Greater NSW and ACT Regional Program, the answer could well be ‘yes’.
Climate extremes are increasing for grapegrowers – and with those extremes comes greater pressure on the production of quality wine grapes.
Drape nets applied in the Hunter Valley trial site.
‘Damage to fruit from hail, sunburn and heatwaves, along with pest impacts at harvest from birds, and more recently kangaroos and bats, is becoming more common across most regions’, said Darren Fahey, Development Officer – Viticulture with the NSW Department of Primary Industries.
He said solutions used by other horticultural sectors – such as permanent netting structures used by the apple and pear industry – were seen as expensive and cumbersome by grapegrowers, given the over-row equipment used in vineyards.
‘So we wanted to investigate an alternative that may be suitable for vineyards – the use of single netted row products, such as draped nets.’
The draped nets used in the trial are UV stable, high-density polyethylene netting with a mesh size of 6mm x 1.8 mm and a unit mass of 60g/m². The mesh size allows for easy application and removal of netting with minimal propensity to catch on things such as clips and post ends.
During the Wine Australia-funded demonstration trial, separate sites in the Hunter Valley (Shiraz trial) and Orange (Chardonnay trial) wine regions assessed differences in temperature/humidity, solar radiation, spray coverage, yield and berry quality differences under white, green and black netting against a control treatment.
‘Given drought conditions governed management across the trial, no data was collected on spray coverage’, Darren said.
However, other findings included:
- Only slight differences in temperature and humidity were recorded between any of the treatments.
- Solar radiation was significantly reduced under the black netting over two seven-day periods at the Orange site. In contrast, the Hunter Valley site saw a declining trend in solar radiation under each of the nets from white, green then black respectively.
- No bird, kangaroo or bat damage occurred under the net treatments. In contrast, the Orange site suffered 80–90 per cent loss of fruit on un-netted adjacent rows from bird damage.
- No hail events occurred during the trial period.
- Berry and bunch weights were slightly increased in all netting treatments above the control at both sites.
- Fruit quality measures resulted in slightly higher malic acid in green and black net treatments above the white net and control treatment at both sites.
- Titratable acidity was increased in green and black net treatments above the white net and control treatment in Chardonnay.
- Reduced anthocyanins and Brix° were observed in the black net treatment in Shiraz below the control. Brix° was also reduced under the green and black net treatments below the white net and control treatment in Chardonnay.
‘This extended trial with the use of protective netting demonstrated a positive benefit of maintaining protection of fruit from heatwave, sunburn and bird damage’, Darren said.
‘Overall, the use of black and green nets had a greater impact than white netting, which was similar to the control.’
Encouragingly, fruit weight was maintained during the trial period – even though it was carried out during a drought.
‘It will be interesting to see how the nets go under a normal vintage, or even in a wet year. Watch this space!’