UVC Lights in Vineyards with Dr Paul Epee of the Bragato Research Institute

This show was published Friday, March 20, 2026

Overview

Dr Paul Epee is a viticulture research scientist at Bragato Research Institute in Marlborough New Zealand. He carries out practical research (not blue sky) to find solutions to deal with issues facing NZ winegrowers.

The project we discuss in this episode is the application of UVC.
Pesticide use has been increasing, 2000 tonnes of fungicide for powdery mildew in 2025. Project to reduce that trend and UV light was thought to be a potential solution that is also environmentally friendly.

We discuss the methodology of the research. It was decided the UV light treatment would be applied at night. When UV light applied is to the plant during the day it is as a preventative method, to help the vine build up immunity to the fungi and develop a response. During the night, the application is curative. The infection is already happening and it is the intensity of the UV light that kills the pathogens in the powdery mildew.

They carried out 6 different trials:

1. As the control, they took the spray programme of their grower who was applying fungicide every 10 days.
2. 20 day return period for fungicide spraying, i.e. reducing the 10 day frequency by half
3. They applied the UV treatment every 10 days
4. They applied the UV treatment every 5 days
5. Alternated fungicide spray with UV treatment: A combination of spraying every 10 days, then UV treatment the next 10 days
6. Alternated spraying every 5 days, then UV treatment every 5 days

Key outcomes

- with spraying, the 20 day return performed almost as well as every 10 days and both were better than using a combination of fungicide and UV light.

- UV light treatment worked only up until pre-bunch closure (before veraison), meaning UV applications need to be made before that stage so that each berry is protected from infection.

- UV light did not work on its own every 20 days. During the trial, this methodology was abandoned in favour of applying every 10 days.

- UV light every 5 days worked well only up to pre-bunch closure. After veraison, the frequency did not work.

The research has left a question mark over the use of UV light which in the trials, only really performing up until veraison, after which the disease threshold is too high at 15%. Further research and funding is needed to discover if that threshold could be reduced and the project (as of February 2026) is currently on hold.

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