New Zealand UVC trials show promise

Trials in New Zealand are exploring whether UVC (ultraviolet-C) light can help control vineyard diseases like powdery mildew, with early results showing potential but not yet conclusive results. These trials are being led by Dr Paul Epee and colleagues at the Bragato Research Institute (BRI).

UVC is a short-wavelength form of ultraviolet light known to damage the DNA of fungal pathogens, preventing their reproduction. That same mechanism makes it effective in disinfection applications in other sectors and underpins its use in viticulture research.

Trial Approach and Early Findings
The Marlborough-based vineyard trial uses an autonomous mobile robot (a UVEX system on a Burro platform) to deliver UVC light along vine rows, primarily at night when fungal pathogens are less able to repair UV-induced DNA damage.

In the first year of the trial:
UVC light applied every five days at about 120 J/m² showed some control of powdery mildew on Sauvignon Blanc vines up to bunch closure

From veraison to harvest, UVC alone was less effective than a standard fungicide programme

The trial identified two concerns, firstly protection only worked while the grape clustered were open. Once the berries swelled the light did not penetrate into the cluster and mould spores spread. The second was that after fermentation, wines appeared to have an altered chemical makeup, in particular methopyrosines which produce Sauvignon Blancs characteristic grassy, herby, green pepper smell was reduced compared to the trial.

Further work needs to be carried out. Improvements in application can be made by using UVC panels that arch over the entire vine. And the dosage of UVC could be considerably higher. Both of these are thought to improve efficacy. However concerns exist about the alteration of Sauvignon Blanc typicity, but further work is required to confirm this.