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A monitoring was conducted in 35 commercial vineyards located in Piedmont (North-West Italy) in September 2018 to test the sensitivity of Botrytis cinerea populations to the fungicides that were commonly used in the past and at present: benzimidazoles, dicarboximides, anilinopyrimidines, phenylpyrroles, hydroxyanilides and SDHI fungicides. Sensitivity was tested by evaluating the spore germination on a medium amended with a discriminatory concentration of the different tested botryticides. Conidial suspensions were prepared from infected, randomly sampled bunches and used for the tests. In comparison with the years 2008–2014, the following trend was recorded: benzimidazole resistance was quite stable and was found in about 50% of the vineyards involved in the monitoring; dicarboximide resistance had disappeared in the tested samples, while the frequency of resistance to anilinopyrimidines had increased; the resistance to fenhexamid had decreased; in the case of boscalid, the presence of resistance was quite stable; no resistance to phenylpyrroles was found, although the high discriminatory dose used for fludioxonil cannot exclude the presence in the tested vineyards of low levels of resistance to this fungicide, typical of multidrug-resistant strains.

The reduction of antimicrobial treatments and mainly the application of environmentally friendly compounds, such as resistance elicitors, is an impelling challenge to undertake more sustainable agriculture. We performed this research to study the effectiveness of non-conventional compounds in reducing leaf fungal attack and to investigate whether they influence the grape phyllosphere. Pathogenicity tests were conducted on potted Vitis vinifera &ldquo, Nebbiolo&rdquo, and &ldquo, Moscato&rdquo, cultivars infected with the powdery mildew agent (Erysiphe necator) and treated with three elicitors. Differences in the foliar microbial community were then evaluated by community-level physiological profiling by using BiologTM EcoPlates, high throughput sequencing of the Internal Transcribed Spacer (ITS) region, and RNA sequencing for the viral community. In both cultivars, all products were effective as they significantly reduced pathogen development. EcoPlate analysis and ITS sequencing showed that the microbial communities were not influenced by the alternative compound application, confirming their specific activity as plant defense elicitors. Nevertheless, &ldquo, plants were less susceptible to the disease and presented different phyllosphere composition, resulting in a richer viral community, when compared with the &ldquo, plants. The observed effect on microbial communities pointed to the existence of distinct genotype-specific defense mechanisms independently of the elicitor application.

Erysiphe necator is favourably influenced by the increase in temperatures and remains the main pathogen threatening grape in Northern Italy. In the present work, the efficacy of laminarin and calcium oxide in the control of grape powdery mildew was evaluated, comparing them to sulphur. Two tests were carried out on potted grape “Moscato” plants in 2017, and two field trials were carried out in Italy during 2016 and 2017 on a vineyard of the “Moscato” variety. Laminarin and calcium oxide showed, for the first time, to significantly reduce powdery mildew, and this occurred in all trials. However, laminarin was less effective than sulphur in potted trials and in 2016 field trial, and both laminarin and calcium oxide were less effective than sulphur in 2017 field trial.