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

• We examined the efficacy of a new non-toxic elicitor named COS-OGA in plant protection.
• COS-OGA efficacy was tested against powdery mildew in vineyards and cucumbers.
• We report a significant reduction of the powdery mildew severity in all of the trials.
• Because COS-OGA is an elicitor, incidence was reduced to a lesser extent than severity.

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.