Natural Oils and Decoctions Produced in the Vineyard as Plant Protection Products for Viticulture Under the Climatic Conditions of Poland

Abstract

Seven disease control products produced at a grapevine farm in Mała Wieś (Masovian County, Poland) were tested and compared with standard chemical control and no control. The following substances were used as disease control agents: lavender, lemon, and orange oils; Saccharomyces cerevisiae HDT18 yeast fermentation liquid; mint; and Habanero Orange hot pepper decoction. Results were compared with treatments using standard fungicides, a control without control, and two commercial products containing tansy extract and chili and garlic extract. The tested products were generally less effective in protecting against fungal diseases than the standard chemical control. However, they improved total yield, yield used for vinification, total acidity, sugar content, and pH of harvested grapes compared to untreated grapes. Our own preparations (HDT-18, lemon oil, mint decoction, and hot pepper) reduced total yields and simultaneously reduced the number of grapes infected with diseases, which is particularly important in mechanical harvesting without sorting. Must parameters (sugar, pH, TA) enabled wine production from each of the experimental combinations tested. These approaches may be useful in organic farming programs in cold climates. Although they may reduce total yields, they also reduce the number of grapes unsuitable for vinification.

1. Introduction

Viticulture in Poland continues to grow dynamically. It is spreading throughout the country, not only in the best regions with the best climatic and soil conditions, located in the southwestern part of Poland [1] but also in traditional apple-growing regions. This may be due to decreasing rainfall and increased resistance of vines to water shortages, high temperatures, and their profitability [2,3,4]. The COVID-19 pandemic has significantly contributed to the development of locally produced and factory-produced wine consumption, during which interest in consuming this type of alcoholic beverage in Poland has increased [5,6]. The profitability of this type of activity in Poland has been demonstrated by vineyards such as “Turnau”, “Niemczańska”, and “55-100” [7]. The current report of the National Support Centre for Agriculture [8] indicates the registration of 651 vineyards and 503 wine producers producing wine from grapes grown in Poland.

More and more often, consumers of local products also care about their lower impact on the natural environment, choosing those produced organically or in a sustainable system. Organic farming has been a challenge in agriculture for many years, and numerous studies are being conducted on grape growing conditions [9,10,11,12,13], which are one of the factors shaping the quality of wine [14]. Safeguarding and exploiting natural biodiversity can allow the development of innovative winemaking practices and the production of valuable wine styles, with tangible economic imperatives [12]. The use of pesticides in viticulture is not advisable, and the overuse of insecticides is often associated with toxicological and environmental problems, with neurotoxic insecticides or insect growth regulators in particular being suspected of causing human disease [15]. As a consequence, such products have been banned in the European Union, which is why biological preparations are sought. Resistance to insecticides and acaricides is a major concern, although in viticulture, this problem is more frequent for fungicides. Pest resurgence and pesticide-induced pests have represented additional implications of insecticide use in viticulture. For this reason, environmentally friendly—biological—solutions are sought. The benefits of using biological solutions include greater biological stability and biodiversity of crops and the creation of ecological corridors for beneficial organisms. Various biological substances have also been tested for many years to protect against diseases and pests [16,17]. It should also be emphasized that the grapevine itself contains a number of compounds that inhibit the risk of toxicity of certain substances [18], and it is possible to breed resistant varieties. Various types of protective agents are used, as well as plant extracts, dried herbs, infusions, decoctions, and oil concentrates [19]. Maciejczak and Mikiciuk [7] point to the benefits of sustainable wine production in temperate climates. Using bioactive preparations produced in the vineyard to protect vines is beneficial for the environment and the vineyard. It reduces the costs of purchasing the preparations and has a positive impact on the crop.

There are few reports in the global scientific literature regarding the use of bioprotective products produced in vineyards. In this article, we tried to fill this gap by comparing preparations produced directly in the vineyard with commercially available organic preparations and chemical protection permitted in ecological vineyards. The aim of the study was to evaluate the effect of several protective preparations produced directly in the vineyard, compared to no protection, standard chemical protection, and commercial grapevine protection products, on yield, primarily the yield for vinification, as well as the effect of individual preparations on must quality.

2. Materials and Methods

The cultivation area where the plantations were established is characterized by low rainfall and high temperature. The climatic conditions are typical of central Poland, with an average annual rainfall of 457 mm and temperature of 11.5 °C. In the summer months, the average daily temperature in the cultivation area was 24 °C (

Table 1. Average monthly rainfall and temperature in 2024 in the village of Mała Wieś.

Months	Rainfall [mm]	Air Temperature [°C]
January	27	2
February	29	6
March	44	7
April	36	9
May	10	15
June	48	23
July	40	26
August	109	22
September	41	15
October	30	8
November	31	4
December	12	1

). Meteorological data were collected at a weather station near the crop fields.

The experiment was conducted in two stages. In the first stage, during the 2023 season, several plant protection products produced on the farm were tested on two grape varieties: “Solaris” and “Souvignier gris.” In the second stage, those products that resulted in phytotoxicity or complete flowering failure in the field were discarded, while the remaining products were selected for the main experiment and tested in the 2024 season. In the second stage, four additional grape varieties, “Muscaris,” “Johanniter,” “Regent,” and “Cabernet cortis”, were added to the study.

The field experiment was conducted in spring 2024 in Mała Wieś, Grójecki district, Mazovia region, Poland, in a young vineyard in its second year after planting and first year of fruiting. In the vineyard, tests were carried out on grape varieties with greater resistance to fungal diseases: PIWI (ger. pilzwiderstandsfähige Rebsorte), the white grapes ‘Solaris’, ‘Muscaris’, ‘Souvignier gris’, and ‘Johanniter’ and the red grapes ‘Regent’ and ‘Cabernet cortis’.

Field studies were conducted in the form of strict field experiments, with 4 repetitions for each combination and 20 plants per plot, using the split-blocks method. For plots, healthy plants without diseases, deficiencies, or other defects were selected. The effects of the studied factors on must pH, total acidity, and sugar content were analyzed on fresh juice (all on Lysa 5000 by Anton Paar, Anton Paar GmbH, Ashland, MN, USA and Vinmetrica SC-300 Bentley Instruments, Inc. Chaska, MN, USA), and both total yield and yield usable for vinification were assessed. We measure weight of yield for every plot by analytical balance.

Each application followed the recommended organic farming methodology, using 500 liters of spray solution per hectare. The organic preparations used were HDT18, citric oil, orange oil, mentha piperita, hot pepper, lavender oil, and “chili & garlic.” The oils were mixed with water continuously during the treatments, creating an emulsion. Use of the preparations depended on the grape variety. Control treatments without protection were sprayed with tap water, while the full chemical protection treatment was sprayed according to grapevine recommendations.

Commercial products available on the market for professional users in Poland, as well as home-made products, were used in the experiments. The commercial products were “chili & garlic” and “wrotycz.” All were produced by AGROBIOS (Nowy Tomyśl, Poland). “Chili & garlic” is an extract obtained by fermenting garlic, chili pepper, ginger, and turmeric with lactic acid bacteria and Bacillus. “wrotycz” is extract from the fermentation process of tansy with Lactobacillus and Bacillus bacteria. These are ready-made preparations, available commercially, recommended by the manufacturer as an alternative to classic preparations. Copper- and sulfur-based products, such as Siarkol extra and Miedzian 50 WP, were used as standard protection. The products were prepared according to the attached process data sheets. A spray rate of 500 L per hectare was used, based on the size of the experimental plots and the application per plot, using new backpack sprayers with electric drive and a pressure of 2.0 atm. The self-made preparations were prepared according to the following recipes. For HDT 18, 1 L of water of temp. 30 °C, 10 g of sugar, and 5 g of Yeast saccharomyces cerevisiae (Lafarge, Paris, France) were all mixed in glass and fermented for 3 days; fermentation was carried out until it stopped naturally, then the mixture was drained. For citric oil, 20 drops of citric natural oil (Oleaia, Warsaw, Poland) was mixed with 1 L of water. For mentha decoction, 1 kg of fresh mint leaves was cooked in 2 L of water for 4 min and left to cool and then drained, used at a dilution of 1:10. For orange oil, 20 drops of orange natural oil (Oleaia, Warsaw, Poland) were mixed with 1 L of water. For hot pepper, 100 g of dried hot pepper ‘Habanero orange’ was cooked in 1 L of water for 4 min and left to cool and then drained and used at a dilution of 1:10. For lavender oil, 20 drops of lavender essential oil (Lavandula angustifolia), home-made on the Island of Vis, Croatia, were mixed with 1 L of water.

Total soluble solids were analyzed using a PAL-1 refractometer (Atago, Bellevue, WA, USA). Measurements were made in duplicate and reported in °brix.

Titratable acidity (TA) was assessed through titration using an Orion Star T910 titrator (Thermo Fisher Scientific, Beijing, China), following the Polish standard PN-90/A-75101/04 [20]. A 0.1 N NaOH solution was gradually added to the samples until a pH of 8.1 was reached, with the process being monitored by an automated pH titration system. The analysis was repeated three times, and the results were expressed as grams of tartaric acid per 1 L.

Standard chemical protection was carried out in accordance with the recommendations of the grapevine protection program for 2024. Siarkol 800 SC was used twice a season, Ridomil Gold MZ Pepite 67.8 WG once a season, and Miedzian 50 WP once a season.

Analyses of fungicide residues were performed by PN-EN 15662:2018-06 [20].

Statistical analyses were performed with Statistica 14 (Statsoft, Tulsa, OK, USA). Data visualizations were performed using Python 3.10 in Jupyter Notebook with Pandas 1.5.3 (by Anaconda, Inc., Austin, TX, USA) within the Anaconda environment. Factorial analysis of variance (ANOVA) with Tukey’s HSD post hoc test (p < 0.05) was performed to compare the results.

3. Results

All tested biological plant protection combinations were less effective than conventional chemical protection, but they did not have a negative impact on the environment—we did not observe any visual negative effects, such as burn symptoms or deformation of plants or the growing environment. The selected preparations had variable effects on yield quality and quantity. Yields were not reduced in a year of examination, and all grapes remaining on the vines reached full maturity.

3.1. ‘Solaris’ and ‘Muscaris’

The tested varieties were sprayed with a preparation containing Saccaromyces cerevisiae HDT18 (Lafarge) yeast killer toxins and an emulsion containing citric oil. The third tested preparation was a commercially purchased preparation, “wrotycz”, containing tansy extract. We obtained a higher yield from ‘Solaris’, both in total yield and in yield of grapes useful for wine production (

Table 2. Yields of ‘Solaris’ and ‘Muscaris’ cultivars under different testing combinations.

Cultivar	Combination	Total Yield [kg·trunk−1]	Yield Use for Vinification	Valid Yield [kg·trunk−1]
		[kg·trunk−1]
‘Solaris’	no prev.	2.35 b*	2.05 b	0.30 b
	chemical c.	2.80 c	2.80 c	0.00 a
	HDT 18	2.40 b	2.35 c	0.05 a
	citric oil	2.20 a	1.90 b	0.30 b
	“wrotycz”	2.10 a	0.50 a	1.60 c
‘Muscaris’	no prev.	0.80 c	0.60 b	0.20 b
	chemical c.	0.85 c	0.80 c	0.05 a
	HDT18	0.80 c	0.80 c	0.00 a
	citric oil	0.70 b	0.50 b	0.20 b
	“wrotycz”	0.50 a	0.25 a	0.25 b
Mean for cvs.	‘Solaris’	2.37 b	1.92 b	0.45 a
	‘Muscaris’	0.83 a	0.59 a	0.50 a
Mean for combination	no prev.	1.56 bc	1.33 b	0.25 b
	chemical c.	1.83 d	1.80 d	0.03 a
	HDT18	1.60 c	1.58 c	0.03 a
	citric oil	1.45 b	1.20 b	0.25 b
	“wrotycz”	1.30 a	0.53 a	0.93 c

Chemical c.—classic chemical protection; no prev.—without protection; * means with the same letters are not significantly different.

). The waste yield was similar, indicating that the percentage of damaged grapes was higher for ‘Muscaris’ than for ‘Solaris’. Here, total yield refers to the weight of all grapes harvested, while the valid yield refers to the weight of grapes without clear symptoms of fungal diseases, undamaged grapes, and grapes suitable for vinification.

HDT18 treatment of both grape varieties resulted in the same yield as untreated grapes, while tansy and lemon oil treatments reduced overall yield. HDT18 achieved 86% of the yield achieved by chemical treatment but significantly higher than the untreated control, with a low percentage of grapes infected with fungal diseases. Use of the HDT18 preparation on grapes of both cultivars (mean for combinations) resulted in the same yield as that obtained under no protection, while the application of tansy and citric oil reduced the total yield. HDT18 achieved 86% of the yield of chemical control but significantly higher than the untreated control, with a low percentage of grapes affected by fungal diseases and a good yield of useful grapes. The same trend was observed for ‘Muscaris’, where the HDT18 preparation performed as effectively as the chemical treatment. The use of “wrotycz” and the citric oil emulsion resulted in a proportion of damaged fruit as high as that obtained when protection was omitted.

For both cultivars, the most beneficial organic preparation was HDT18, for which the yield was slightly reduced compared to chemical protection but still greater than when protection was omitted. The tansy preparation not only reduced the yield but also increased the mass of defective clusters, making it completely useless for the protection of grapes. The defective clusters were full of destroyed berries, which had fungal disease and were fully oxidized inside.

3.2. ‘Souvignier gris’ and ‘Johanniter’

These varieties were treated with mint decoction and orange oil emulsion. In this case, the ‘Souvignier gris’ variety produced significantly higher yields—3.5 times higher than the ‘Jo-hanniter’ variety (

Table 3. Yields of ‘Souvignier gris’ and ‘Johanniter’ cultivars under different testing combinations.

Cultivar	Combination	Total Yield [kg·trunk−1]	Yield Use for Vinification [kg·trunk−1]	Valid Yield [kg·trunk−1]
‘Souvignier gris’	no prev.	2.35 b*	2.05 b	0.30 b
	chemical c.	2.80 c	2.80 c	0.00 a
	mentha d.	2.40 b	2.35 c	0.05 a
	orange oil	2.20 a	1.90 b	0.30 b
‘Johanniter’	no prev.	1.00 a	0.70 a	0.30 c
	chemical c.	1.15 b	1.10 c	0.05 a
	mentha d.	1.05 a	1.00 b	0.05 a
	orange oil	1.15 b	1.00 b	0.15 b
Mean for cvs.	‘Souv. gris’	3.59 b	3.43 b	0.16 a
	‘Johanniter’	1.09 a	0.95 a	0.14 a
Mean for combination	no prev.	2.42 c	2.20 b	0.33 c
	chemical c.	2.48 c	2.40 c	0.08 a
	mentha d.	2.33 b	2.25 b	0.08 a
	orange oil	2.13 a	2.00 a	0.13 b

Chemical c.—classic chemical protection; no prev.—without protection; mentha d.—mentha decoction; * means with the same letters are not significantly different.

)—indicating that the ‘Souvignier gris’ variety is less sensitive to the treatments used.

The effects of using these preparations were not the same on both varieties. For ‘Souvignier gris’, orange oil emulsion significantly reduced the yield compared to the absence of protection and the crushed decoction, while no such effect was observed for ‘Johanniter’. The total yield after using orange oil was the same as that with chemical protection. Use of the mint decoction enabled the collection of the same number of good grapes as chemical protection for ‘Souvignier gris’ while decreasing defective yield. In the case of ‘Johanniter’, however, both preparations yielded more good fruit than with no protection and less than with traditional protection methods. When comparing the individual protection methods, it should be noted that both preparations reduced the total yield; however, for mint, total yield was the same as that obtained under no protection with fewer diseased groups.

3.3. ‘Cabernet cortis’ and ‘Regent’

‘Regent’ produced slightly higher yields (

Table 4. Yields of ‘Cabernet cortis’ and ‘Regent’ cultivars under different testing combinations.

Cultivar	Combination	Total Yield [kg·trunk−1]	Yield Use for Vinification [kg·trunk−1]	Valid Yield [kg·trunk−1]
‘Caberent cortis’	no prev.	1.40 c*	1.00 b	0.40 c
	chemical c.	1.40 c	1.30 c	0.10 b
	hot pepper	1.10 a	1.10 b	0.00 a
	lavender oil	1.25 b	1.10 b	0.15 b
	“chili & garlic”	1.30 b	0.50 a	0.80 d
‘Regent’	chemical c.	1.80 bc	1.70 c	0.10 a
	no prev.	1.75 b	1.50 b	0.25 b
	hot pepper	1.50 a	1.45 b	0.05 a
	lavender oil	1.60 ab	1.50 b	0.10 a
	“chili & garlic”	1.50 a	1.10 a	0.40 c
Mean for cvs.	‘C. cortis’	1.29 a	1.00 a	0.29 b
	‘Regent’	1.63 b	1.45 b	0.18 a
Mean for combination	no prev.	1.56 c	1.25 b	0.33 c
	chemical c.	1.60 c	1.35 b	0.10 b
	hot pepper	1.30 a	1.23 b	0.03 a
	lavender oil	1.43 b	1.30 b	0.13 b
	“chili & garlic”	1.40 b	0.80 a	0.60 d

Chemical c.—classic chemical protection; no prev.—without protection; * means with the same letters are not significantly different.

), but the difference was not as large as in the white varieties tested. Both varieties were treated with a commercial preparation containing chili and garlic extract, lavender oil emulsion, and a home-made Capsicum annum (‘Habanero Orange’) hot pepper decoction.

For the ‘Cabernet cortis’ cultivar, the hot pepper extract reduced the total yield but eliminated diseased clusters (100% elimination), similar to ‘Regent’. In contrast, the commercial preparation containing chili and garlic did not have the same effect. Lavender oil slightly reduced the total yield but reduced the number of diseased clusters for both ‘Cabernet cortis’ and ‘Regent’.

‘Cabernet cortis’ exhibited more diseased clusters due to its greater susceptibility to diseases.

The preparations used influenced the sugar content and pH of the must, while their effect on acidity was negligible (

Table 5. pH, TA, and sugar content (°brix) of ‘Solaris’ and ‘Muscaris’ cultivars under different testing combinations.

Cultivar	Combination	pH of Must	TA [g·L−1]	Sugar °brix
‘Solaris’	no prev.	3.30 b*	5.50 a	21.0 a
	chemical c.	3.00 a	5.70 a	22.1 b
	HDT 18	3.00 a	5.67 a	22.9 c
	citric oil	2.90 a	5.65 a	22.9 c
	“wrotycz”	3.30 b	5.45 a	22.4 b
‘Muscaris’	no prev.	3.45 b	5.45 b	22.7 a
	chemical c.	3.15 a	5.85 a	23.2 b
	HDT18	3.10 a	5.60 a	24.4 c
	citric oil	3.00 a	5.71 a	23.4 b
	“wrotycz”	3.35 b	5.62 a	22.6 a
Mean for cvs.	‘Solaris’	3.10 a	5.60 a	22.3 a
	‘Muscaris’	3.20 a	5.65 a	23.3 b
Mean for combination	no prev.	3.40 b	5.48 b	21.9 a
	chemical c.	3.10 a	5.76 a	22.7 b
	HDT18	3.05 a	5.64 a	23.8 c
	citric oil	2.95 a	5.68 a	23.2 c
	“wrotycz”	3.35 b	5.54 a	22.5 ab

* Means with the same letters are not significantly different.

). A high must pH was recorded for combinations without chemical protection and with the “wrotycz” preparation for both varieties. These combinations also contained less sugar than the others. In contrast, the HDT 18 combination and citric oil significantly increased the sugar content in the grape juice must.

The use of the mint decoction and orange oil did not affect the pH of the must (

Table 6. pH, total acidity, and sugar (°brix) content of ‘Souvignier gris’ and ‘Johanniter’ cultivars under different testing combinations.

Cultivar	Combination	pH	TA [g·L−1]	Sugar °brix
‘Souvignier gris’	chemical c.	2.85 a*	8.95 a	23.2 a
	no prev.	2.80 a	8.30 c	23.0 a
	mentha d.	2.80 a	8.45 bc	23.3 a
	orange oil	2.90 a	8.80 a	23.2 a
‘Johanniter’	chemical c.	2.90 a	8.50 b	22.9 a
	no prev.	2.95 a	8.45 bc	22.9 a
	mentha d.	2.90 a	8.50 b	22.4 a
	orange oil	2.85 a	8.50 b	22.6 a
Mean for cvs.	‘Souv. gris’	2.84 a	8.60 ab	23.2 a
	‘Johanniter’	2.90 a	8.50 b	22.7 a
Mean for combination	chemical c.	2.90 a	8.75 a	23.1 a
	no prev.	2.90 a	8.40 c	23.0 a
	mentha d.	2.85 a	8.50 b	23.1 a
	orange oil	2.90 a	8.65 a	22.9 a

* Means with the same letters are not significantly different.

). The applied treatments did not affect acidity. The ‘Johanniter’ variety accumulated less sugar than ‘Souvignier gris’, though this difference is due to natural varietal differences rather than the applied preparations.

The ‘Cabernet cortis’ and ‘Regent’ cultivars differed in pH, acidity, and sugar content (

Table 7. pH, total acidity, and sugar (^obrix) content of ‘Cabernet cortis’ and ‘Regent’ cultivars under different testing combinations.

Cultivar	Combination	pH	TA [g·L−1]	Sugar °brix
‘Caberent cortis’ n.i.	no prev.	3.20 b*	6.11 a	21.5 a
	chemical c.	2.95 a	6.12 a	21.2 a
	hot pepper	2.90 a	6.15 a	22.1 a
	lavender oil	2.85 a	6.15 a	22.8 a
	“chili & garlic”	3.25 b	6.10 a	21.6 a
‘Regent’	no prev.	3.35 b	5.95 a	23.9 a
	chemical c.	3.00 a	5.90 a	23.6 a
	hot pepper	2.98 a	5.86 a	24.0 a
	lavender oil	3.05 a	5.91 a	23.6 a
	“chili & garlic”	3.40 b	5.90 a	23.2 a
Mean for cvs.	‘C. cortis’	3.03 a	6.11 b	21.84 a
	‘Regent’	3.16 b	5.84 a	23.66 b
Mean for combination	no prev.	3.30 b	6.03 a	22.7 a
	chemical c.	2.98 a	6.01 a	22.4 a
	hot pepper	2.94 a	5.96 a	23.1 a
	lavender oil	2.95 a	6.03 a	23.2 a
	“chili & garlic”	3.30 b	6.00 a	22.4 a

* Means with the same letters are not significantly different.

). The preparation used also influenced pH but had a lesser effect on acidity and sugar content. No statistical differences were observed in these cases.

The ‘Cabernet cortis’ variety had a higher sugar content, which is a feature of this variety compared to the ‘Regent’ variety. In each of these two varieties, the preparations had different effects on the sugar content. For the ‘Cabernet cortis’ variety, the best product was lavender oil, and for the ‘Regent’ variety, the best product was hot pepper. As can be seen, both the variety and the product used influenced the content of the tested ingredients.

4. Discussion

There are few reports in the scientific literature on the use of bioactive preparations in grapevine protection. Therefore, further research is needed on the use of biological plant protection products, which provide better results in cultivation than conventional methods. Combining biological prevention with varieties resistant to fungal diseases can provide satisfactory yields and benefits for the crop. The negative impact of agriculture on the environment requires a change in the approach and concept of pest control in vineyards. Disease-resistant varieties are recommended in organic farming, as demonstrated in this experiment. Of the tested varieties, ‘Muscaris’ responded least effectively to biological protection, which is inconsistent with the resistance and resistance to fungal diseases reported by Wang et al. [21]. In their study, Wang et al. [21] demonstrated that ‘Muscaris’ is a relatively new Vitis vinifera variety with good resistance to musk dew, powdery mildew, and gray mold. However, data presented in a report by the State Wine Institute in Freiburg [22] indicate that the fungal resistance of the ‘Muscaris’ cultivar is low.

In our study, the disease susceptibility and yield of the cultivar ‘Souvignier gris’ were similar to those reported by Casanova-Gascón et al. [23], who confirmed the high suitability of the ‘Souvignier gris’ cultivar for organic farming due to its high resistance to fungal diseases. The report [22] indicates that the white cultivars ‘Solaris’, ‘Souvignier gris’, and ‘Johanniter’, as well as the red variety ‘Caberent cortis’, are disease-resistant.

Among the preparations, treatments with Saccharomyces cerevisiae HDT18, mint decoction, and hot pepper decoction proved beneficial. HDT18 is a yeast clone commonly used in winemaking to reduce sulfur consumption. This is due to the killer toxins produced by this yeast clone. This is why such good results were achieved with this preparation. Studies conducted by Lisek et al. [24] demonstrated a significant positive effect of organic fertilizers and biostimulants on the growth, yield, and health of the Solaris and Regent grape varieties. These studies confirm the validity of the assumptions that biopreparations are useful in viticulture. They may stimulate yield to a lesser extent, but they are environmentally friendly. Using “wrotycz” causes higher pH in must, which can cause problems with diseases stabilization during fermentation time.

Experiences gathered by Viret et al. [25] from the protection of organic vineyards in Switzerland demonstrate significant potential for the use of biopreparations for protection against arthropods and fungi. The authors of the study state that in the case of fungal diseases, only resistant varieties should be considered to achieve good results. All V. vinifera grape varieties are sensitive to mildews (Plasmopara iticola and Erysiphe necator) and request spraying at regular intervals to ensure quality yields. The approaches with natural products, the reinforcement of natural defense mechanisms like phytoalexins, and the use of biodynamic preparations contribute to partial efficacies and therefore require generally more spraying to control diseases. In order to optimize the use of fungicides, the time of spraying, the choice of the active ingredient, and proper application on the target are the key elements in efficacy while reducing the impact on the environment.

Studies by Yildirim et al. [26], conducted in the laboratory and in the vineyard, using various chemical preparations, demonstrated the effectiveness of fungal protection. All tested chemicals showed low efficacy against foliar infection. However, bunch infection was inhibited by applying a fungicide alternating KH₂PO₄—di-1-p-menthene and a mixture of KH₂PO₄ + sulfur(s) (WP).

Each of the preparations that reduced the number of infected bunches could be useful for plantations that use combines to harvest, as at this vineyard, but they could also be used prior to hand-harvesting. Reducing clusters being damaged during mechanical harvesting can significantly alter the quality of the must when manual selection is not performed. In this case, eliminating defective clusters on the vine is crucial to the quality of the must and wine. The higher number of infected grapes observed with the use of commercial organic preparations is unfavorable and may indicate low quality or high contamination. This encourages the use of self-made preparations.

The preparations used did not significantly affect the quality of the must in terms of the pH, acidity, or sugar content. A tendency towards a higher, unstable pH was observed in varieties more severely infected with diseases, suggesting that these combinations may not be suitable for further study. The vast majority of the tested preparations did not have a negative impact on the quality parameters of the must.

5. Conclusions

In the case of PIWI, it is possible to replace synthetic plant protection products with natural, home-made products in the vineyard. Although the use of such products can reduce overall yield, they often eliminate damaged fruit, allowing for mechanical harvesting and resulting in grapes more suitable for vinification. Commercially prepared products had a significant negative impact on good-quality yields, while solutions prepared in-house in the vineyard proved more beneficial.

Particularly favorable results were achieved using products containing HDT 18 yeast, mint, and chili pepper decoction. The least favorable results were obtained with orange oil, tansy, chili pepper, and garlic, which are not recommended for use in vineyards with the tested varieties. The use of home-made products and their positive effect on grapes, which reduce the number of infected berries, allows for the use of combine harvesters, which contributes to a significant reduction in raw material acquisition costs.