Synthetic pesticides are widely used to protect crops from pathogens and pests, especially for fruits and vegetables, and this may lead to the presence of residues on fresh produce. Improving the sustainability of agriculture and, at the same time, reducing the adverse effects of synthetic pesticides on human health requires effective alternatives that improve the productivity while maintaining the food quality and safety. Moreover, retailers increasingly request fresh produce with the amounts of pesticides largely below the official maximum residue levels. Basic substances are relatively novel compounds that can be used in plant protection without neurotoxic or immune-toxic effects and are still poorly known by phytosanitary consultants (plant doctors), researchers, growers, consumers, and decision makers. The focus of this review is to provide updated information about 24 basic substances currently approved in the EU and to summarize in a single document their properties and instructions for users. Most of these substances have a fungicidal activity (calcium hydroxide, chitosan, chitosan hydrochloride, Equisetum arvense L., hydrogen peroxide, lecithins, cow milk, mustard seed powder, Salix spp., sunflower oil, sodium chloride, sodium hydrogen carbonate, Urtica spp., vinegar, and whey). Considering the increasing requests from consumers of fruits and vegetables for high quality with no or a reduced amount of pesticide residues, basic substances can complement and, at times, replace the application of synthetic pesticides with benefits for users and for consumers. Large-scale trials are important to design the best dosage and strategies for the application of basic substances against pathogens and pests in different growing environments and contexts.

Pathogens and pests constantly challenge food security and safety worldwide. The use of plant protection products to manage them raises concerns related to human health, the environment, and economic costs. Basic substances are active, non-toxic compounds that are not predominantly used as plant protection products but hold potential in crop protection. Basic substances’ attention is rising due to their safety and cost-effectiveness. However, data on their protection levels in crop protection strategies are lacking. In this review, we critically analyzed the literature concerning the field application of known and potential basic substances for managing diseases and pests, investigating their efficacy and potential integration into plant protection programs. Case studies related to grapevine, potato, and fruit protection from pre- and post-harvest diseases and pests were considered. In specific cases, basic substances and chitosan in particular, could complement or even substitute plant protection products, either chemicals or biologicals, but their efficacy varied greatly according to various factors, including the origin of the substance, the crop, the pathogen or pest, and the timing and method of application. Therefore, a careful evaluation of the field application is needed to promote the successful use of basic substances in sustainable pest management strategies in specific contexts.

Les problématiques posées par les intrants sous leurs diverses formes ont récemment bénéficié d’une plus large prise en compte, et d’un gain d’intérêt auprès du grand public et des autorités compétentes. Cette demande sociétale se traduit par une augmentation et une diversification des solutions alternatives aux intrants d’origine chimique, que ce soit avec les produits de biocontrôle pour la protection des plantes, la fertilisation ou la biostimulation. Les autorités publiques cherchent donc à cadrer l’utilisation de ces nouveaux intrants à l’aide de réglementations nationales en publiant décrets et arrêtés. C’est ainsi qu’en France est née la catégorie des Préparations naturelles peu préoccupantes (PNPP) en 2006. Cette catégorie contient les substances de base, mais aussi les substances naturelles à usage biostimulant ayant récemment fait l’objet d’une modification d’ampleur de leur réglementation, dont nous analysons ici les conséquences en termes de nombre de substances autorisées. La liste des Substances naturelles à usage biostimulant la plus exhaustive possible est obtenue à partir de différents documents officiels concernant les plantes considérées comme alimentaires pour l’être humain et l’animal. L’augmentation considérable du nombre de substances naturelles à usage biostimulant est une opportunité pour les agriculteurs et représente une évolution sans précèdent dans la réglementation, passant d’une approche positive avec des substances explicitement autorisées, à une approche négative où certaines substances sont interdites et toutes les autres sont autorisées. Cet article tente d’éclaircir la situation en permettant aux agriculteurs de disposer d’une base de données de plantes utilisables sans crainte que la substance ou la plante ne soit considérée comme non alimentaire par les autorités, et donc soumise à d’autres contraintes.

Consumer demand, retailer involvement, policies to reduce pesticide application, and the growth of organic agriculture are steering research toward safer alternatives like basic substances: compounds used as food, food ingredients, or in medicine with a potential secondary application in plant protection. Downy mildew (DM) and powdery mildew (PM) are major grapevine diseases, and many fungicide applications are required for their management. In this 2-year field trial, chitosan, whey, sweet orange essential oil (EO), Equisetum arvense, Urtica spp., and Ampelomyces quisqualis were tested against DM and PM in repeated stand-alone treatments (10 applications in 2022 and 11 in 2023) on cultivar Montepulciano in Italy. Their effectiveness was compared with copper and sulfur. Untreated plants and water-sprayed plants served as two negative controls. The disease McKinney Index was calculated based on incidence and severity, following visual assessments. Several compounds reduced the amount of DM and PM. Chitosan 0.5% and sweet orange EO 600 ml/hl provided the highest protection levels, reducing the DM McKinney Index on leaves up to 94 and 91% compared with the untreated control. Against PM, both treatments achieved a 98% reduction. Reductions on bunches were up to 72 and 47% for DM and 40 and 37% for PM. For two consecutive years and under high disease pressure, chitosan proved as effective as copper in managing DM on both leaves and bunches. This trial explored some natural compounds as additional tools for DM and PM management. Further studies are crucial to validate their effectiveness across different environments, disease levels, and cultivars.