Fighting vineyard pathogens with UV light

by | Jan 30, 2020 | South Africa Wine Scan

The aim of this project was to determine if UV light can be used to reduce or eliminate the incidence of powdery and downy mildew in vineyards.

Project layout:

Two different UV light treatments (100 J/m2 and 200 J/m2) were applied weekly to Chardonnay vines using a UV light array on a tractor drawn carriage. Based on previous laboratory trials, it was expected that these treatments should stop 80% – 100% of the powdery mildew conidia from germinating.
Treated vines received only UV light, no other fungicides.
In another treatment, vines received only conventional fungicides.
There was also a control where no fungicides or UV light were applied.
The trial was done in a year where powdery mildew pressure was moderate and downy mildew pressure was severely high.


Powdery mildew

– Severity of powdery mildew in the control vines were 15%.
– Both UV treatments significantly reduced the severity of powdery mildew on berries to 5%.
– Fungicide treatments reduced severity to 1%.

Downy mildew

– Both UV treatments suppressed foliar downy mildew better that the conventional fungicides.

Preliminary results also indicated that UV treatments can suppress mite populations.

Significance of the study:

It is widely known that there is increasing pressure on growers to reduce the use of fungicides and pesticides. Resistant varieties is still a new field and consumers’ reaction to unknown varieties is a concern. Using UV light has promising potential to be an alternative to fungicides in an integrated management strategy.


The Potential of Light Treatments to Suppress Certain Plant Pathogens and Pests, David M. Gadoury, Research Focus 2019-2: Cornell Viticulture and Enology.

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