COS-OGA: A novel oligosaccharidic elicitor that protects grapes and cucumbers against powdery mildew

Abstract Many plant protection products have been banned due to their toxicity or because pathogens have become resistant to their active substances. Plant resistance inducers are a promising class of compounds that will hopefully reduce dependence on harmful chemicals for plant protection. The efficacy of COS-OGA, a novel elicitor composed of a complex of oligochitosans and oligopectates as active substances, has been assessed in production conditions against powdery mildew on grapevines and on cucumbers. COS-OGA induced a large reduction in the severity of powdery mildew for both crops. At the end of vineyard trials, COS-OGA, at a spraying rate of 37.5 g ha −1 , achieved a considerable reduction in Uncinula necator severity on bunches of grapes with 78% protection in France and 76% protection in Spain. Similarly, in the last evaluation performed in greenhouses to assess the protection of cucumber crops against Sphaerotheca fuliginea , COS-OGA at 25 g ha −1 LWA (leaf wall area) yielded a 72% reduction in leaf disease severity in Belgium and 69% in Spain. In some trials, the efficacy of the COS-OGA active substance was even higher than the conventional chemical reference.