Organic Viticulture Research Articles

Comparative life cycle assessment of integrated and organic viticulture based on a long-term field trial in Germany

Comparative life cycle assessment of integrated and organic viticulture based on a long-term field trial in Germany

Impact of Natural Phytosanitary Product Residuals on Yeast Fermentation Performance and Wine Composition.

Although phytosanitary treatments are necessary to protect grapes from parasitic diseases, consumers are increasingly concerned about the use of synthetic phytosanitary products and their possible residues in wine. Pre-harvest phytosanitary treatments are often inevitable, and consequently downtime is required to avoid possible residues on the grapes. Instead, natural phytosanitary products, such as essential oil (EO)-based products, can be applied close to the harvest without specific restrictions, with results that are not only technically convenient but also more attractive for the consumers. Because of the high antimicrobial activity of EO products, in the present study we evaluated the effect of different residual amounts of two new EO-based phytosanitary products on the alcoholic fermentation and the chemical composition of the final fermented products. In particular, two EO-based new formulations, exploitable in organic viticulture management, were evaluated. Increasing concentrations of each formulation were tested during laboratory scale fermentations and in comparison with synthetic and natural commercial phytosanitary products. Growth and fermentation kinetics of a commercial yeast strain of Saccharomyces cerevisiae and the chemical and sensory profiles of the final products were evaluated. Both new formulations showed no significant impact on the growth and fermentation kinetic of S. cerevisiae at any of the concentrations tested. In all trials, alcoholic fermentation was completed in 15 days. Instead, a different chemical composition of the final products was observed. Therefore, these new products might represent an interesting alternative tool to the conventional phytosanitary treatments, being applicable close to the harvest without negative impacts on the kinetics of alcoholic fermentation and also being more acceptable to wine consumers.

Efficacy of using grape cane extracts against <i>Plasmopara viticola</i> under field conditions and their impact on the composition of berries and musts of <i>Vitis vinifera</i> L. cv. Riesling

Grapevine downy mildew caused by Plasmopara viticola is a deleterious vine disease currently controlled using synthetic and copper-based fungicides. Environmental concerns surrounding such fungicides necessitate sustainable alternatives like grape cane extracts. However, studies into their efficacy and effects on the product remain limited. This study aimed to assess the open-field efficacy of a novel grape cane extract formulation, alone and combined with a copper agent, against downy mildew, and to examine its impact on berry and must composition. The results were compared to standard fungicides frequently used in integrated and organic viticulture. In 2022, the grape cane extract formulation reduced downy mildew severity by 78 % on berry clusters, comparable to the maximum acceptable dose of copper for organic farming in Germany (3 kg/ha/a). Combining the grape cane extract with the copper agent was more effective than the copper agent alone, but not more effective than the grape cane extract alone. In 2023, disease development was marginal, despite artificial inoculation. Compositional differences detectable by FTIR were insignificant between musts derived from all treatments, increased copper levels were observed whenever copper had been applied. The phenolic content in freeze-dried, de-seeded berries of 2022 was significantly lower after copper (14.6 mg/g dry weight DW) and grape cane extract treatments (6.6 mg/g DW) when compared to the control (36.1 mg/g DW), with discrepancies in stilbenoid and flavan-3-ol levels in particular, as analysed by HPLC-DAD. However, these differences were not confirmed in 2023, with results showing no correlations between different treatments and phenolic contents. These findings suggest that applications of the phenolic grape cane extract do not lead to artificially altered levels or relevant residues of the active constituents; i.e., the phenolic compounds in the product. In brief, grape cane extracts might represent a promising natural alternative to controlling grapevine downy mildew, particularly in organic viticulture, which, to date, heavily relies on (eco-)toxic copper-pesticides. Further multi-year studies including wine analyses are warranted to follow the entire flow towards the final product.

COPPEREPLACE 1. Copper applications in organic viticulture are a real challenge today. Part 1 - Scientific Activities

In grape and wine production, one of the main relevant and recurrent diseases is downy mildew caused by the fungus (Plamospara viticola). It is frequently present in wine production worldwide, with a significant high annual incidence in some regions. Since the discovery of Bordeaux mixture (copper sulphate and lime) in the 1880’s, many formulations based on copper (Cu) have been developed and used in viticulture production. https://coppereplace.com/.

Foliar Resistance to a Natural Population of Plasmopara viticola in Some Grapevine Varieties Grown in Türkiye

ABSTRACTIt is critical to use a population of the pathogen that contains different strains to determine the resistance of grapevine varieties to the downy mildew pathogen Plasmopara viticola in a specific region. This study tested six local grape varieties (Çavuş, Kalecik Karası, Müşküle, Papaz Karası, Sultana and Yapıncak), eight Turkish registered varieties (Barış, Bozbey, Güzgülü, Özer Karası, Reçel Üzümü, Tekirdağ Çekirdeksizi, Trakya İlkeren and Yalova İncisi) and seven varieties of foreign origin (Cabernet Sauvignon, Cardinal, Chardonnay, Cinsault, Isabella, Semillon and Gamay) using detached leaf and leaf disc assays with pathogen populations collected from vineyards. There was a significant correlation for disease severity between the two assay methods. No sporulation was observed on the varieties Çavuş and Isabella in both assay methods. The variety Yapıncak had very low disease severity (2.00%) in the leaf disc assay, and the pathogen did not sporulate on this variety in the detached leaf assay. Cluster analysis was performed to determine the resistance level of the varieties against the pathogen, as different disease severities were observed in some varieties depending on the test method used, and the 21 varieties were classified into four clusters. Barış, Bozbey, Cardinal, Çavuş, Isabella, Semillon and Yapıncak in Cluster I exhibited the lowest disease severity mean (2.88%), while those in Cluster 3, including Cabernet Sauvignon, Güzgülü, Papaz Karası and Yalova Incisi, had the highest disease severity mean (56.75%). These varieties in Clusters 1 and 3 were considered highly resistant and highly susceptible, respectively. Leaf hair density, as reported in official variety descriptions, did not associate with reduced disease severity in the two assays. This study assessed the response of grapevine varieties to the P. viticola population in the region for the first time. The highly resistant and resistant varieties identified will provide new material for breeders and contribute to the improvement of organic viticulture in the area.

Copper (II) Level in Musts Affects Acetaldehyde Concentration, Phenolic Composition, and Chromatic Characteristics of Red and White Wines.

Copper (II), a vital fungicide in organic viticulture, also acts as a wine oxidation catalyst. However, limited data are currently available on the impact that maximum allowed copper (II) ion doses in wine grapes at harvest can have on aged wine quality. This was the focus of the present study. We investigated the copper (II) effects by producing both white and red wines from musts containing three initial metal concentrations according to the limits set for organic farming. In detail, the influence of copper (II) on fermentation evolution, chromatic characteristics, and phenolic compounds was evaluated. Interestingly, the white wine obtained with the highest permitted copper (II) dose initially exceeded the concentration of 1.0 mg/L at fermentation completion. However, after one year of storage, the copper (II) content fell below 0.2 ± 0.01 mg/L. Conversely, red wines showed copper (II) levels below 1.0 mg/L at the end of fermentation, but the initial copper (II) level in musts significantly affected total native anthocyanins, color intensity, hue, and acetaldehyde concentration. After 12-month aging, significant differences were observed in polymeric pigments, thus suggesting a potential long-term effect of copper (II) on red wine color stability.

To what extent can a phase-out of pesticides in viticulture be achieved? Learning from the efforts of a large farm network after 10 years

In accordance with European Directive 2009/128/CE, France has set up national policies to curb the reliance of agriculture on phytosanitary inputs. The DEPHY network is one such initiative;, which has been designed to drive, support and document the fieldwork of 3,000 farms voluntarily taking part in a collective input reduction programme. This study aimed to describe the achievements of the network’s viticultural sector, as its perennial crop is heavily reliant on pesticide applications. We chose a sample of 343 wine-growing systems across mainland France, analysed records of their vineyard operations from before they joined the network, and compared them to those from the 2017-2020 period. We used the Treatment Frequency Index (TFI) to assess pesticide reliance together with other techno-economical parameters: production costs, workloads, greenhouse gas emissions and disease control. A significant decrease in pesticide use was found over the whole study period, with, for instance, an average TFI reduction of 24 %, which is consistent with national objectives but unmatched outside of the network. We observed an overall shift towards pesticide inputs with lower repercussions on health or the environment, as well as different TFI reduction trajectories based on initial pesticide dependency. We described the alternative practices introduced to the systems, and our results suggest that reductions in pesticide use stem from quite small and minor changes made to the cropping systems. These new practices only slightly lowered the vineyards’ technical and economical performances in specific situations involving an indepth revamping of the systems; e.g., conversion to organic viticulture. To increase pesticide phase-out, further research is needed on redesigning cropping systems, and on how to scale up the network’s results to the national level.

Below-ground arthropod diversity in conventional and organic vineyards: A review

Viticulture is one of the most important agricultural sectors in the Mediterranean area but also one with substantial impact on the soil ecosystem. Some of the most common practices in viticulture, such as tillage, inter-row management, fertilization and use of pesticides, can have important effects on soil communities. The latter significantly contribute to several fundamental soil processes such as decomposition, nutrient and carbon cycling, and microbiota regulation. In perspective, it is therefore necessary to assess the effects of agronomical practices on soil biological communities. The increasing shift towards organic viticulture is seen as a promising management model to maintain soil functionality and preserve soil biodiversity. Below, we present an appraisal of the main practices in conventional and organic viticulture and their possible effects on soil mesofauna. Understanding the extent to which organic practices contribute to maintaining/altering soil functionality and biodiversity is a fundamental step towards the development of an environmentally sustainable viticulture.

Improving organic grape production: the effects of soil management and organic fertilizers on biogenic amine levels in Vitis vinifera cv., 'Royal' grapes

BackgroundThe integration of organic viticulture practices in grape cultivation represents a pivotal advancement towards sustainable agriculture, emphasizing the importance of environmentally friendly methods that enhance soil health, grape quality, and overall ecosystem biodiversity, thereby contributing significantly to the resilience and long-term sustainability of viticultural ecosystems. This study explored the effects of soil management practices, including chisel, disc harrow, and no tillage, as well as the impact of utilizing Antep radish, broccoli, and olive blackwater as fertilizer applications, on the biochemical composition, specifically biogenic amines (BAs), in the clusters of the 'Royal' grape cultivar within a vineyard setting.ResultsThroughout the three-year study, no tillage soil management consistently emerged as the most influential soil treatment for enhancing BAs in 'Royal' grape berries, especially in combination with Antep radish and olive blackwater fertilizer applications. Among fertilizer applications, the nontreated control vines consistently had the highest concentrations of critical BAs, such as putrescine, cadaverine, histamine, and dopamine, across different soil management practices. Among the soil management practices and fertilizer applications evaluated, the disc harrow soil management and olive blackwater fertilizer application generally yielded the lowest concentrations of BAs across several metrics.The PCA biplots indicated that experimental years have a similar effect on BA content in grape berries, with specific amines such as serotonin and dopamine being more affected in 2020, while cadaverine, histamine, spermidine, trimethylamine, and norepinephrine were more influenced in 2021, and putrescine, spermine, agmatine, and tryptamine in 2022.ConclusionThese findings hold significant implications for organic agriculture, emphasizing the nuanced influence of soil management practices and organic fertilizers on the BA composition of grape berries. Our results indicate the potential of tailored agricultural strategies to enhance plant health and quality, aligning with the principles of sustainability and environmental stewardship inherent to organic farming.Graphical

РЕАЛИЗАЦИЯ ПРИОРИТЕТНЫХ НАПРАВЛЕНИЙ НАУЧНО-ТЕХНИЧЕСКОЙ ДЕЯТЕЛЬНОСТИ «ВННИИВиВ «МАГАРАЧ» РАН» В ОБЛАСТИ ВИНОГРАДАРСТВА В 2023 ГОДУ

Research is presented that contributes to an increase in the production of domestic grape and wine products, including in the system of organic farming. The object of research is grapes of native, classical and breeding varieties. The research was carried out on the basis of the Center for collective use of the Ampelographic collection «Magarach», as well as in industrial plantations of the Crimea according to generally accepted and original methods. Characteristics of 50 varieties for the database, 4 sources of valuable traits were obtained, genotyping of wild grapes was performed, 99 allele variants were identified. Optimal concentrations of substances for the development of proembryogenic calluses and cells in suspension cultures were selected. The influence of biologically active substances on the development of heart shaped and torpedo shaped embryos has been established. The obtained 6 transgenic lines of the Podarok Magaracha variety were adapted to in vivo conditions to assess their cold resistance and frost resistance. In the vegetative collection of plants in vitro, samples are maintained under conditions of active and slow growth. An aseptic culture of 14 grape varieties was obtained. The molecular diagnosis of the latent form of phytopathogens of plant material after the recovery procedures was carried out. The biovar Agrobacterium tumefaciens was identified by the method of molecular diagnostics. During molecular diagnostics, the Rupestris stem pitting virus was detected in the samples. New knowledge has been gained about the dynamics of changes in the quality indicators of grapes depending on the variety and region of cultivation against the background of a complex of agro-climatic parameters and indices used to isolate terroirs. Varietal-rootstock combinations have been identified. The formation of datasets has continued in order to train neural networks for the detection of harmful organisms and pathologies of the development of grape plants. The technology of organic viticulture production for autochthonous varieties and varieties of the Magarach Institute breeding has been tested. The technology of storing table grapes based on the use of calcium-containing preparations has been optimized. For the first time, an information technology of cross-platform integration has been developed for the implemented hardware and software complex for photo-fixation and neural network detection of the number of pests in specialized «traps».

Copper toxicity on Eisenia fetida in a vineyard soil: a combined study with standard tests, genotoxicity assessment and gut metagenomic analysis

Copper (Cu) toxicity is a pressing concern for several soils, especially in organic viticulture. The objective of this work was to assess Cu toxicity on the non-target organism Eisenia fetida, employing both traditional and novel tools for early identification of Cu-induced damages. In addition to traditional tests like avoidance and reproductive toxicity experiments, other tests such as the single cell gel electrophoresis (SCGE) and gut microbiome analysis were evaluated to identify early and more sensitive pollution biomarkers. Four sub-lethal Cu concentrations were studied, and the results showed strong dose-dependent responses by the earthworm avoidance test and the exceeding of habitat threshold limit at the higher Cu doses. An inverse proportionality was observed between reproductive output and soil Cu concentration. Bioaccumulation was not detected in earthworms; soil concentrations of potentially bioavailable Cu were not affected by E. fetida presence or by time. On the contrary, the SCGE test revealed dose-dependent genotoxicity for the ‘tail length’ parameter already at the second day of Cu exposition. Gut microbiome analysis a modulation of microbial composition, with the most aboundant families being Pectobateriaceae, Comamonadaceae and Microscillaceae. Bacillaceae increased over time and showed adaptability to copper up to 165 mg/kg, while at the highest dose even the sensitive Acetobacteriaceae family was affected. The research provided new insights into the ecotoxicity of Cu sub-lethal doses highlighting both alterations at earthworms’ cellular level and changes in their gut microbiota.

Searching new targets for the control of Black Rot: following the role of host factors modulating the infection process of Phyllosticta ampelicida.

Black Rot is a grapevine disease caused by the ascomycete Phyllosticta ampelicida. Neglected so far, this is developing into a pertinent problem in organic viticulture as resistant varieties are still lacking. Here, we follow cellular details of the infection process in the susceptible vinifera variety Müller-Thurgau and screen the ancestral European wild grapevine (V. vinifera sylvestris) for resistance to Black Rot. Using a standardized infection assay, we follow fungal development using LTSEM and quantify key stages on different hosts using fluorescence microscopy. There is considerable variation in susceptibility, which is associated with more rapid leaf maturation. Hyphal growth on different carbon sources shows a preference for pectins over starch, cellulose or xylans. In the resistant sylvestris genotypes Ketsch 16 and Ketsch 18 we find that neither spore attachment nor appressorium formation, but hyphal elongation is significantly inhibited as compared to Müller-Thurgau. Moreover, defence-related oxidative burst and accumulation of phenolic compounds is stimulated in the resistant genotypes. We arrive at a model, where more rapid maturation of the cell wall in these sylvestris genotypes sequesters pectins as major food source and thus block hyphal elongation. This paves the way for introgression of genetic factors responsible for cell wall maturation into V. vinifera to develop Black Rot-resistant varieties of grapevine.

Sulfur — a potential additive to increase the efficacy of copper-based fungicides against grapevine downy mildew

Control of downy mildew on grapevines in organic viticulture in Europe is mainly based on using copper-based fungicides. However, the effect of these agents is often insufficient to prevent losses when infestation pressure is high. The addition of sulfur, which is primarily used to control powdery mildew, improves the effect of copper on downy mildew. In three out of five trial years, sulfur had a clear positive effect when it was added during spray treatments against Plasmopara viticola, the causal agent of downy mildew on grapevines. This was evident mainly in the fruits; no further positive effect on the leaves was evident. In addition, the present study shows that copper-based fungicides are effective on leaves but have a rather poor effect on grapevine fruit. Furthermore, the study demonstrates that the effect of copper is significantly worse than that of the chemical synthetic contact fungicide folpet.

Tracing the origins of phosphonate residues in organic vineyards: A novel analytical approach

In the European Union, organic viticulture faces enormous challenges in controlling grapevine downy mildew since the ban on inorganic phosphonates or phosphonic acid in 2013. However, inorganic phosphonate is still detected in organic wines, although the responsible winegrowers often pledge that they had not sprayed phosphonate-containing products in their vineyards. Among several hypotheses on the origin, the emergence of phosphonate from the soil, e.g., due to preceding applications or from contaminated groundwater, is in discussion. This study investigates whether an analytical differentiation of the origin of phosphonate in the plant or the final product might be feasible by examining leaf and petiole tissue. A total of 908 leaf and petiole samples of various grapevine cultivars were collected from a container vine experiment as well as from four experimental vineyard sites in Germany, on which phosphonate was either sprayed onto the plants as part of crop protection (all experiments), applied to the soil (container experiment only) or present as residue from previous applications (vineyard experiments). Phosphonate concentrations in leaves and petioles depended strongly on whether plants had been sprayed or had taken up phosphonate from the soil. Therefore, an index was created and tested using independent datasets from different geographical locations, based on the concentrations found in leaves and petioles. Index accuracy was at 99.1% correct classifications when distinguishing phosphonate origin from the soil versus that from foliar spraying. Furthermore, phosphonate uptake from the soil was shown to allow considerable phosphonate concentrations in the berries and musts, rendering associations of phosphonate residues in wines with accusations of an actual foliar application highly questionable. In brief, our data and index might provide an approach for identifying the source of phosphonate contamination in the grapevine plant and, if suitable sample material is available, also the related products.

Promising Paths of the Development of Organic Viticulture

The article deals with the state and the promising paths of the development of organic viticulture. The main distinctive features of organic production technologies are highlighted. The experience of the exploitation of organic vineyards in Russia is analyzed.

Exploring entomopathogenic nematodes for the management of Lobesia botrana (Lepidoptera: Tortricidae) in vineyards: Fine-tuning of application, target area, and timing

Lobesia botrana (Lepidoptera: Tortricidae) is a crucial grapevine pest worldwide. Expanding the available biocontrol agents can provide new management strategies compatible with organic viticulture. Entomopathogenic nematode (EPN) potential as a biocontrol agent was demonstrated against various developmental stages of L. botrana. For its field application, we hypothesised that by selecting the best combination of EPN-adjuvant and identifying the best area/timing for their application, we will secure their effective implementation against L. botrana. The aim of this study was to determine the best ecological scenarios for their use against L. botrana. We investigate three EPN species naturally occurring in Riojan vineyards: Steinernema feltiae, S. carpocapsae, and Heterorhabditis bacteriophora. We evaluated (i) EPN viability, infectivity, and adherence on leaves combined with adjuvants (Multi-Us, Maximix, Dash HC, Nu-Film-17, and Adrex), (ii) EPN biocontrol against L. botrana larva on leaves and grapes and damage reduction, and (iii) EPN efficacy against L. botrana at 22°, 15°, and 10 °C. Overall, all the adjuvants were compatible with the EPN, except Adrex with Heterorhabditis bacteriophora. Compared with the no application, EPNs (steinernematids) alone or with Maximix increased L.botrana L3 mortality on grapes and leaves, thereby reducing the damage. Pupal mortality caused by steinernematids EPN (alone or with Maximix) decreased with temperature, from ∼60% at 22 °C to <30% at 10 °C. Overall, steinernematids EPN (alone or with Maximix) applied against L. botrana on leaves, grapes, or trunks reduced the damage and increased insect mortality. This study suggests the best-case scenario for the application of EPNs is at sunset during late spring/early autumn at mid-temperatures (22 °C-15 °C). Further field validation is necessary for their full implementation.

Consistent benefits of fungicide reduction on arthropod predators and predation rates in viticulture: a five-year experiment

For reliable pest suppression, benefits of habitat management for natural enemies of agricultural pests need to be consistent over time. Unfortunately, most research projects allow only for one or two years of data collection. Here, we present a five-year study on effects of fungicide reduction and altered plant architecture on arthropod abundances and natural pest control in an experimental vineyard. The vineyard rows were divided into eight groups, half of which were trained in vertical shoot position (“trellis system”) and the other half as semi-minimal pruned hedge (“minimal pruning”). Every row was divided in three sections receiving three different plant protection intensities, respectively, with fungicides certified for organic viticulture. In each year we sampled arthropods from the grapevine canopy by standardized leaf collection and beat-sheet sampling, and exposed baits of a major grapevine pest (Lobesia botrana) to assess natural pest control. Arthropods, in particular predators, benefited from reduced fungicide sprayings and in turn promoted natural pest control. In contrast, effects of minimal pruning were less strong, and restricted to the leaf mesofauna, earwigs and leafhoppers. Across the five study years with their variable weather conditions, we conclude that the advantages of reduced fungicide sprayings in fungus-resistant varieties are consistent over time.

Effects of vineyard management, herbaceous cover and vine plant characteristics on bird diversity in a North African agroecosystem

AbstractFollowing the demand for organic wines and ecological practices, organic viticulture has increased dramatically in recent decades. The effect of agricultural practices on organic and conventional vines on bird diversity has not been studied in North Africa. In this study, we analysed the impact of the management method, season, herbaceous cover and vine plant size on bird diversity in organic and conventional vineyards. Our findings show that organic agriculture has a positive impact on bird diversity compared with conventional vineyards. Bird diversity changes with the seasons, being higher in winter, autumn and spring than in summer. Compared with conventional vineyards, the diversity of birds was higher on the organic vineyards in autumn, winter and spring. In summer, the differences between organic and traditional agriculture became negligible. Thus, the increased percentage of grass cover had a positive effect on bird diversity. Furthermore, bird diversity decreases with increasing vine plant size. The findings of this research are promising in this regard. We promote continued research into this aspect of using grassland cover and intensity of tillage as a tool to conserve wildlife and support indigenous species.

Combining Trichoderma koningiopsis and chitosan as a synergistic biocontrol and biostimulating complex to reduce copper rates for downy mildew control on grapevine

Plasmopara viticola, causal agent of downy mildew and one of the most severe grapevine diseases, is commonly controlled by multiple fungicide applications, primarily based on copper compounds in organic viticulture. Biostimulants and biocontrol agents could make a major contribution to pesticide reduction. A synergistic biocontrol and biostimulating complex consisting of Trichoderma sp. and chitosan was investigated to achieve copper fungicide reduction in the control of P. viticola. To ensure complex efficacy, the interactions and effects of all agents need to be investigated at the tri-trophic level of grapevine, downy mildew, and biocontrol and biostimulating complex. To guarantee the compatibility of Trichoderma sp. and chitosan, the chitosan tolerance of different copper-tolerant Trichoderma isolates was investigated in mycelial growth and germination tests. A T. koningiopsis isolate proved to be highly chitosan-tolerant was identified for further studies. The timing of spray application with T. koningiopsis and various chitosans was evaluated for efficacy against P. viticola. In the period 0 to 1 day before inoculation with the pathogen, the formation of the sporangia number was significantly reduced by the tested agents. To further describe the mode of action and efficacy of T. koningiopsis and chitosan against P. viticola, the application of single agents on upper and lower grapevine leaves inoculated with the pathogen in comparison to resistance inducers and copper fungicide were tested. Moreover, the combination of T. koningiopsis with different chitosans and a reduced copper rate was investigated on the respective leaf sides of greenhouse plants. Both, a direct and indirect mode of action against downy mildew was demonstrated. Regardless of the treated leaf side, sporulation of downy mildew was clearly inhibited compared to the untreated control. Moreover, microscopic images showed successful establishment of T. koningiopsis and uniform distribution of chitosan on leaves. The tested biocontrol and biostimulating complex might show a promising combatting tool against P. viticola while simultaneously reducing copper rate.

Additive and synergistic antifungal effects of copper and phenolic extracts from grape cane and apples.

Organic viticulture seeks sustainable alternatives for eco-toxic copper fungicides to control downy mildew caused by Plasmopara viticola. (Poly)phenol-rich extracts of agricultural byproducts are known to possess antifungal activity, but high production costs often limit their actual implementation. We developed and produced novel ligninsulfonate-based grape cane extract (GCE) formulations and an apple extract on a pilot plant scale, including a detailed (poly)phenol characterization by high-performance liquid chromatography photodiode array mass spectrometry (HPLC-PDA-MS). Our GCE formulations alone reduced downy mildew disease severity in greenhouse trials by 29%-69% in a dose-dependent manner, whereas a standard application of the copper-based agent alone reached ~56%. When applied together, disease severity was diminished by 78%-92%, revealing a synergistic effect that depended on the mixture ratio. Combining GCE formulations with the apple extract, additive effects were found (80% disease severity reduction). The studied plant extracts are proposed to both substitute for and synergistically reinforce copper fungicides in grapevine downy mildew control. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.