Use of Chitosan and Other Natural Compounds Alone or in Different Strategies with Copper Hydroxide for Control of Grapevine Downy Mildew

Abstract

Grapevine downy mildew (GDM) is one of the most serious diseases of grapevines. Limitations for the use of copper-based products in organic agriculture according to EU Regulation EU/2002/473 and the later EU Commission Implementing Regulation 2018/1981 has promoted a search for alternatives. This 5-year field trial evaluated the effectiveness against GDM of several strategies using different chitosan-based formulations and application rates in comparison with other natural compounds, with these applied individually or with copper hydroxide. Trials were run in commercial vineyards, with different environmental conditions and grapevine cultivars. For the natural compounds applied as individual treatments, a 0.5%/0.8% chitosan formulation provided the best protection against GDM, with the other compounds and formulations less effective. When copper hydroxide use was halved by combination with these natural compounds according to three different strategies, GDM incidence, severity and McKinney Index were reduced, in particular for copper hydroxide applied in combinations with the 0.5%/0.8% chitosan formulation, rather than with a mixture of laminarin and Saccharomyces spp. extract. The 0.5%/0.8% chitosan formulation alone and with copper hydroxide provided good protection against GDM for both high-pressure and low-pressure disease seasons. Chitosan thus represents a good alternative to copper formulations for control of GDM for both organic and integrated disease management.

COS-OGA Applications in Organic Vineyard Manage Major Airborne Diseases and Maintain Postharvest Quality of Wine Grapes

“…Romanazzi et al [27] reported the effectiveness of laminarin and Saccharomyces extracts mixtures and chitosan alone in reducing downy mildew in vineyards although to a lesser extent if compared to copper compounds. Furthermore, chitosan confirmed similar performances against P. viticola both under high and low disease pressures [28].…”

Copper Monitoring in Vineyard Soils of Central Italy Subjected to Three Antifungal Treatments, and Effects of Sub-Lethal Copper Doses on the Earthworm Eisenia fetida

“…Moreover, at the European level, research has been promoted on alternative products to supplement or substitute cupric fungicides, focusing on natural compounds registered as plant protection products (PPP) or plant biostimulants [38]. Among the substitutes for copper in the antifungal fight in the vineyard, growing interest is observed for chitosan as it is a biocompatible, biodegradable, and non-toxic polymer molecule [39].…”

Basic Substances, a Sustainable Tool to Complement and Eventually Replace Synthetic Pesticides in the Management of Pre and Postharvest Diseases: Reviewed Instructions for Users

“…In some conditions basic substances were already at farm level, with a level of pest management not different than the standard. Just as example, chitosan hydrochloride was also applied in commercial conditions, in the field, and postharvest treatments, and several studies proved that it could have an effectiveness comparable to some commercial PPPs [ 42 , 48 ]. Basic substances, probably less efficient and practical to use than other active substances authorized as PPPs, are known and used by producers since decades as substitution means and have already demonstrated their effectiveness.…”