There are many possible incentives for farmers to decrease use of synthetic pesticides and fungicides. Some of these reasons might be: to achieve organic certification, environmental or worker safety reasons, to decrease likeliness of resistance development in pests, to save money, or a variety of other reasons. In practice, this objective can sometimes be difficult to achieve while maintaining maximum crop yield and quality. Scientist Raúl F. Guerrero and some of his colleagues from Andalusian Institute of Agricultural and Fisheries Research and Training (IFAPA) have begun exploring a new approach as an alternative to applying synthetic pesticides to wine grapes pre-harvest. Their technique involves applying ultraviolet UV-C light to grapes pre-harvest in order to increase the grapes’ natural immunity responses to fight disease.
UV-B light has been shown to successfully reduce or stop germination of Powdery Mildew spores on grape leaves, but the use of UV-C light in this experiment is distinct. The purpose is not to directly target a specific disease, but rather to increase the immunity responses in the grapes, which could help prevent a variety of infections. The UV-C light stimulates production of stilbenoids, which have been shown to have an antifungal response, among other benefits.
Researchers tested two treatments: one treatment of grapes received five minutes of UV-C exposure every day for three days pre-harvest, and the other treatment received only five minute UV-C exposure. The treatment with multiple exposures had an 86-fold increase in stilbenoid concentrations. There were some effects on grape texture and quality, but the grapes were still high quality. The increased UV-C exposure also accelerated the ripening process.
While these studies are still very preliminary, the results are promising. These researchers have also begun to asses using UV-C light to increase stilbenoid concentrations in grape canes as well, which could potentially reduce the need for synthetic pesticides.
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