Introduction

Grapevine (Vitis vinifera) is one of the most economically valuable and resilient crops in the world. This species originates from temperate climate regions and has a dormancy period of three–five months, typically followed by one pruning and one harvest per year (Xu et al., 2011). However, with advances in technology and new research approaches, it is now possible to cultivate this species in different regions (Limier et al., 2018). Brazil, a tropical country, has become one of the main grape producers in South America, showing significant growth in recent decades, mainly due to the adoption of grafted seedlings, advancements in management techniques, and the development of new cultivars (Favero et al., 2011).

The cultivation of grapevines has become increasingly feasible in tropical regions, but some limiting factors remain. High temperatures and excessive precipitation, for example, can negatively affect important stages of the grapevine cycle, such as flowering and berry ripening, by accelerating these processes and even reducing their duration (Poni et al., 2020; Rafique et al., 2024). As a consequence, negative impacts can be observed in wine characteristics, such as increased alcohol content (de Orduña, 2010) or, conversely, lower sugar accumulation and, consequently, lower alcohol content. The latter occurs because the grape cuticle is more resistant to water entry than to water loss, resulting in dilution of berry contents (Becker & Knoche, 2011). In addition, rainfall directly on the leaves, combined with high temperatures, increases the incidence of diseases such as downy mildew (Plasmopara viticola), which can significantly reduce productivity (Salazar-Parra et al., 2010).

The challenging weather conditions for grapevine cultivation are not restricted to tropical regions, as climate change is causing similar or even more severe effects in many parts of the world (Rafique et al., 2024). Grapevine productivity and fruit quality are directly affected by climatic fluctuations during their growth and development, especially in critical phases such as berry ripening (Nistor et al., 2018; Shah et al., 2021). Due to rising temperatures over time, famous vineyards in the northern hemisphere are considering relocating their cultivation areas to higher altitudes in search of milder climates (Kurtural & Gambetta, 2021). In this context, viticultural practices can be useful to mitigate these challenges, either by preventing problems or by facilitating production through the acclimatisation of plants to such conditions. These practices could be valuable not only in tropical regions but also in many areas worldwide that are affected by climate change.

Two important management techniques are known to improve grapevine cultivation under challenging environmental conditions: double pruning and plastic covering. Double pruning is a technique developed to modify the grapevine cycle, shifting the harvest from summer to winter and resulting in improved quality indices, such as soluble solids, pH, and titratable acidity, in areas where conventional cycle production is often hindered (Regina et al., 2011). This is achieved by performing two pruning within the grapevine cycle: the conventional one after winter and a second during summer (Amorim et al., 2005), when harvest would normally occur. Plastic covering, on the other hand, allows the maintenance of the grapevine cycle by improving microclimatic conditions, preventing the direct incidence of rainfall on the leaves, and reducing the consequent removal of applied fungicides (Holcman et al., 2018).

The benefits of these two management techniques are already known and applied in many regions of Brazil. However, the effects of double pruning under protected cultivation have not been thoroughly investigated, particularly regarding morphological, physiological, and anatomical aspects of grapevine development. This gap in knowledge is highly relevant, since wine quality ultimately depends on the proper establishment of the plant. Therefore, this study aimed to evaluate the addition of plastic covering in a double-pruning vineyard on grapevine physiology, anatomy, and morphology in a tropical region, seeking an effective strategy to optimise production under challenging weather conditions.

Materials and methods

1. Experimental design

The experiment was conducted in the experimental vineyard of the University of São Paulo, Escola Superior de Agricultura “Luiz de Queiroz” (ESALQ), Department of Plant Production, in Piracicaba, SP, Brazil (22° 42' 25" S 47° 37' 41" W; 546 m altitude). The regional climate is classified as Cwa, characterised by a humid subtropical climate with hot, wet summers and dry, mild winters (Peel et al., 2007). The two-year-old vines cv. Sauvignon blanc (Vitis vinifera) grafted onto Paulsen 1103 rootstock (Vitis berlandieri × Vitis rupestris) were planted 1.0 meters between plants and 2.5 meters between rows, in rows of 25 meters. The vines were conducted on a vertical shoot positioning (VSP) system. In parts of the rows, the vines were planted on VSP with a transparent plastic film installed over the plants, and their maintenance consisted of replacement in each cycle. This plastic covering was made of polypropylene film, with a thickness of 200 μm and a solar radiation transmittance rate of 70–80 %.

The experiment was organised into five blocks, with each block containing five vines, resulting in a total of 25 vines per treatment (with and without plastic covering). All the plants were cultivated under a double-pruning management system, totalling four growing cycles (winter 2022, summer 2023, winter 2023, summer 2024). Each cycle was labelled according to the season in which the harvest occurred. As this technique involves two harvests by altering the grapevine cycle, and since many producers in different regions of the country adopt it to harvest twice, this study evaluated plant growth and development across all cycles. All phenological stages of the grapevine were monitored throughout the winter and summer cycles.

2. Environmental monitoring in the vineyard

For temperature measurements, a thermohygrometer was installed both under the plastic covering and outside. Light intensity was monitored using a luxmeter (AK305) in both conditions. Light quality was assessed with a spectrometer (USB2000+RAD/Ocean Optics; wavelength range: 200–850 nm; spectral resolution: 2.0 nm) to verify the spectral distribution of light under both conditions. General meteorological data, such as air temperature and precipitation, were obtained from the meteorological station of ESALQ.

3. Biometric traits and phenological stages

The growth of vines under covered and uncovered conditions was recorded through weekly measurements of 10 vines (two of each block) until the shoots reached the last wire of the vertical trellis system or until growth stabilised. The leaf area (cm²) of individual leaves from each condition, in each cycle, was measured using ImageJ^® software. The leaves were collected from the same bud position after growth had stabilised. The phenological stages were determined according to the BBCH scale, and they were monitored and photographed throughout all cycles (Lorenz et al., 1995).

4. Physiological traits

The physiological parameters of the vines were analysed through leaf gas exchange measurements conducted on sun-exposed leaves from the main shoot of 10 randomly selected vines (two of each block). An infrared gas analyzer (IRGA, LI-6400XT/Li-Cor) was used to measure the photosynthetic rate (A), stomatal conductance (Gs), and leaf transpiration (E). The light saturation point in both covered and uncovered vines was determined by performing a light response curve. The chosen light intensities were 0, 50, 100, 200, 300, 500, 800, 1,000, 1,200, 1,600, 1,800, and 2,000 μmol m^–2 s^–1, with measurements starting from the highest intensity. Regarding pigment content, the chlorophyll a and b indices were determined at the ripening stage in all cycles using a ClorofiLOG (CFL1030). For this analysis, 15 leaves at the same height on the shoot were selected.

5. Anatomical analyses

Leaves from the middle region of the main shoot of five vines from each condition (covered and uncovered) were randomly selected for anatomical analyses. For this purpose, samples from the fourth quadrant of each leaf were cut and fixed in formaldehyde–glutaraldehyde solution (2.5 % glutaraldehyde and 2.5 % formaldehyde in 0.05 M sodium cacodylate buffer with 0.001 M CaCl₂). After dehydration in a graded ethanol series (30 %, 50 %, 70 %, and 100 %, for 15 minutes each), the samples were sectioned into 5 μm slices using a manual rotary microtome (RM2235-Leica) (Marques & Soares, 2022). All images were obtained using a microscope equipped with a camera (ZEISS Axioskop). For scanning electron microscopy (SEM), 1 cm² leaf samples were dehydrated in a graded acetone series (30 %, 50 %, 70 %, and 100 %). Analyses were performed with a scanning electron microscope (JSM-IT300LV-JEOL), allowing for detailed imaging of the leaf epidermis. To quantify stomatal density more efficiently, the leaf impression method was employed by applying nail polish to the abaxial surface of the leaves.

6. Chemical control

Throughout all experimental cycles, disease and pest control were necessary, particularly due to challenging weather conditions that favoured their occurrence. Downy mildew (Plasmopara viticola) was managed through the application of fungicides, including Amistar^© (azoxystrobin, 240 g/ha), Ranman^© (cyazofamid, 300 mL/ha), and Revus^© (mandipropamid, 500 mL/ha).

7. Statistical analyses

For comparison between the covered and uncovered treatments across all experimental cycles, a two-sample t-test was employed. Statistical analyses were performed using Minitab software (version 19.1), ensuring robust and accurate computations. Graphs were generated in Python (version 3.11.5) using visualisation libraries such as Matplotlib and Seaborn.

Results and discussion

1. Environmental conditions

The maximum and minimum air temperatures were generally similar in both experimental years, showing the expected seasonal pattern of increasing temperatures in summer and decreasing temperatures in winter (Figure 1). However, only three days exceeded 35 °C in 2022, whereas in 2023, there were 32 days with such extreme temperatures, likely related to several heat waves during the second semester, coinciding with the fourth cycle. During the experimental years of 2022 and 2023, the highest precipitation levels occurred in the summer, primarily in January, coinciding with the harvest period of the conventional cycle. In contrast, the lowest precipitation levels were recorded in July of both years, corresponding to the winter cycle harvest. Summer rainfall accounted for approximately 65 % of the total precipitation in 2022 and around 48 % in 2023, coinciding with critical stages of the summer cycle, such as fruit ripening and harvest (Figure 1).

Excessive rainfall can negatively affect production due to direct water contact with leaves, as the combination of high moisture and elevated temperatures creates ideal conditions for pathogen development, increasing disease incidence. For example, Plasmopara viticola, the causal agent of downy mildew, completes its life cycle in 5–18 days and can significantly reduce yield (Koledenkova et al., 2022). Consequently, management strategies that mitigate these conditions, such as the use of plastic coverings, have become increasingly necessary.

The maximum photosynthetic photon flux density (PPFD) recorded outside the plastic covering was 1,820 μmol m^–2 s^–1 at 1 p.m., while under the plastic covering, the maximum was 1,362 μmol m^–2 s^–1 at the same time, indicating that the plastic reduced PPFD by approximately 30 %. Since the light saturation range for grapevines is 800–1,200 μmol m^–2 s^–1 (Carvalho et al., 2016), plants outside the plastic were exposed to excessive light levels (Figure 2). Plants can mitigate light stress by activating photoprotective mechanisms in response to reactive oxygen species (ROS) generated in the photosynthetic apparatus (Mullineaux et al., 2006). When these mechanisms are insufficient, photoinhibition can occur, reducing photosynthetic efficiency (Rizhsky et al., 2002). Consequently, plastic coverings have increasingly been used in different regions of tropical areas to reduce excessive sunlight. For example, studies in different Brazilian states have reported PPFD reductions of up to 45 % in Rio de Janeiro (de Almeida et al., 2020), 15 % in Minas Gerais (de Souza et al., 2015), and 34 % in Rio Grande do Sul (Comiran et al., 2012). This reduction can enhance vine growth and development by lowering the risk of photoinhibition.

The temperature dynamics at the experimental site were also notable. During the warmest hours of the day (9 a.m.–3 p.m.), air temperatures outside the plastic covering were higher than those inside, while at the beginning and end of the day, temperatures under the plastic were approximately 3 °C higher than outside. Under peak conditions, the plastic covering could reduce temperature by up to 3 °C (Figure 2). The literature reports variable effects of plastic coverings on vineyard microclimates. De Almeida et al. (2020), for instance, observed a ~7 % increase in maximum air temperature in covered vineyards, while Pedro Júnior et al. (2011) reported no differences compared to uncovered systems. Marigliano et al. (2022) observed that during a heatwave, temperatures in the berry region of uncovered vines reached 58 °C, while plastic covering mitigated this extreme heat. These discrepancies likely result from differences in plastic type, transmission rate, and thickness. Nonetheless, it is clear that plastic coverings alter vineyard microclimates.

Regarding light quality, differences were observed only in the UV-B range (280–315 nm), while the visible spectrum necessary for photosynthesis remained unaffected (Figure 3). Similarly, Chavarria et al. (2009) reported a 50 % reduction in UV radiation under plastic coverings. Higher UV-B exposure in uncovered conditions can negatively affect plants by reducing photosynthetic rate, stomatal conductance, and photosystem II efficiency, among other processes (Martínez-Lüscher et al., 2013). Therefore, strategies that mitigate UV-B radiation are useful not only in tropical regions but also in areas increasingly affected by climate change.

2. Biometric traits

Interestingly, at the beginning of the cycle, vines in both conditions exhibited very similar growth rates, and in some cycles, no significant differences were observed (Figure 4). However, as the vines developed, differences in growth rate became increasingly apparent. Across all experimental cycles, the highest growth rates were consistently recorded in vines grown under plastic covering, with the greatest difference observed in the final cycle (summer 2024), where covered plants in the last week of analysis were 117.3 % taller than uncovered plants (Figure 4).

Vines in uncovered conditions were exposed to challenging environmental factors, including excessive light, high midday temperatures, and direct rainfall. Extreme light and temperature can negatively affect plant physiology, causing disorders such as sunburn, degradation of photosynthetic pigments, increased polyphenol accumulation, and loss of aroma compounds (Gambetta et al., 2021). Additionally, high temperatures combined with direct rainfall increase the incidence of diseases, such as downy mildew (González-Rodríguez et al., 2011). Under such stress, plants often reduce or suspend growth through a finely tuned “growth-defence trade-off” (Figueroa-Macías et al., 2021), which likely explains the reduced growth rate observed in uncovered vines. Several studies support these observations. Comiran et al. (2012) reported faster growth in covered vines, associated with higher thermal accumulation, whereas higher disease incidence was observed in uncovered vines. Similarly, de Souza et al. (2015) found that covered vines grew approximately 6 cm per day, compared to less than 4 cm per day in uncovered vines. These findings are consistent with the present study, highlighting that microclimate modification via plastic covering can improve growth conditions and promote vine development.

Vines grown under plastic covering consistently produced larger, darker green leaves compared to uncovered vines across all experimental cycles. The final cycle (summer) recorded the maximum leaf area, with covered vines reaching approximately 115 cm², whereas uncovered vines reached about 65 cm² (Figure 5). Similarly, a study conducted in southeastern Brazil reported larger leaf area in covered vines, which was associated with higher carbon assimilation and increased yield (de Souza et al., 2015). Another study in the same region also observed greater carbon assimilation in covered vines, attributed to their larger leaf area (de Almeida et al., 2020).

The winter cycles had similar overall durations: the first cycle occurred in 2022, lasting 115 days, and the second occurred in 2023, lasting 117 days. The summer cycles had a longer duration, with the 2023 cycle lasting 134 days and the 2024 cycle lasting 130 days (Figure 6). However, fruit ripening was faster during the summer cycles, taking 18–30 days, compared to 33–46 days in the winter cycles. Sauvignon blanc is a cultivar characterised by late bud break, and its growth cycle can vary between 115 and 170 days in Brazil (Borghezan et al., 2011; Radünz et al., 2015; Leão et al., 2024). This period can vary depending on the specific climate and growing conditions of the vineyard. A longer time to bud break was observed in the summer cycles (19–29 DAP; Days After Pruning), compared to the winter cycle (7–10 DAP) (Figure 6). Since winter cycle pruning is done during the summer, when temperatures are higher, and pruning is performed on a higher bud (5th–6th), these factors likely accelerated the beginning of bud break.

The phenological stages of grapevines vary depending on the cultivar, management techniques, and prevailing weather conditions (Rafique et al., 2024). The maximum temperatures influence significantly important stages, as budbreak and bloom, while average temperatures are more important for later season events, as fruit ripening and harvest (Alikadic et al., 2019). In fact, this could be observed in this study, where budbreak occurred faster in winter cycles, with higher maximum temperatures (~32 °C) during this stage, if compared with summer cycles, where the pruning was done during maximum temperatures lower (~26 °C). Consequently, this early budbreak probably influenced the inflorescences to appear earlier. On the other hand, the fruit ripening was faster during summer cycles, where the average temperature during this stage was constantly higher.

One of the few experiments studying the cultivation of cv. Sauvignon blanc and other cultivars under double-pruning management showed that harvest during the conventional grapevine cycle (summer cycle) had to be advanced due to the incidence of diseases in the bunches (da Mota et al., 2011). The authors noted that the higher incidence of diseases was attributed to the elevated precipitation commonly experienced in the summer. In fact, higher precipitation was observed during the harvest of the summer cycles (Figure 2), but the use of plastic covering prevented the onset of bunch diseases. As a result, ripening was influenced solely by temperature. This suggests that plastic covering can mitigate the negative impacts of excessive rainfall on grape quality.

3. Physiological traits

Covered and uncovered vines exhibited distinct physiological traits throughout the experimental cycle. Across all cycles, covered vines showed higher photosynthetic rate (A), stomatal conductance (Gs), and transpiration rate (E) compared with uncovered vines (Figure 7). This indicates that covered vines were more actively photosynthesising and transpiring. All these processes are strongly influenced by light, of which 80–90 % of the transmitted spectrum is required to sustain photosynthesis, flower differentiation, and fruit ripening (Novello & de Palma, 2008). These findings suggest that the microclimatic alterations caused by plastic covering did not impair key physiological processes such as photosynthesis.

Several studies have also investigated whether plastic covering in vineyards impacts plant physiology. For example, an experiment conducted in Minas Gerais state with cv. Syrah demonstrated that covered vines did not show differences in A, Gs, and E compared with uncovered vines (de Souza et al., 2015). Similarly, another study in Brazilian vineyards found no effect of plastic covering on these parameters (de Almeida et al., 2020). In California, USA, an experiment with cv. Cabernet-Sauvignon under different types of plastic coverings also reported no significant effects on photosynthetic performance (Marigliano et al., 2022). On the other hand, a study conducted in southern Brazil with cv. Cabernet-Sauvignon observed a higher maximum photosynthetic rate in covered vines (16.7 μmol m^–2 s^–1) compared to uncovered vines (14.2 μmol m^–2 s^–1), along with increased stomatal conductance (Mota et al., 2009). The authors associated this improvement with a 44 % reduction in UV radiation under the covering, consistent with the findings of the present study.

Interestingly, the light response curves developed under both conditions showed that covered and uncovered vines reached similar light saturation levels, at 1,200 μmol m^–2 s^–1 (Figure 8). However, differences emerged at this saturation point, where covered vines reached a higher photosynthetic rate (17.5 μmol m^–2 s^–1) compared with uncovered vines (13.5 μmol m^–2 s^–1) (Figure 8). The lower photosynthetic rate observed in uncovered vines is likely associated with unfavourable conditions such as excess light, direct rainfall, and increased disease incidence. Furthermore, uncovered vines were more exposed to UV-B radiation, which is known to negatively affect photosynthesis and stomatal conductance (Martínez-Lüscher et al., 2013).

Covered vines also exhibited significantly higher chlorophyll (chl) a and b indices throughout all experimental cycles compared with uncovered vines (Figure 9). This likely explains the darker green leaf colouration observed under plastic covering. Similar patterns were reported in southern Brazil, where cv. Moscato Giallo grown under plastic covering showed increased chl a content (Chavarria et al., 2009). A comparable trend was observed with cv. Syrah in southeastern Brazil, where covered vines exhibited higher leaf chl content (de Souza et al., 2015). The authors attributed this effect to reduced light transmission through the covering material. Interestingly, a study conducted in Egypt also reported higher chlorophyll content in covered vines (Doaa, 2018).

These changes in pigment indices under plastic covering were expected. Chlorophyll plays a fundamental role in photosynthesis by absorbing the light energy required for the process (Mao et al., 2007). However, under unfavourable conditions such as excessive sunlight, damage to the chlorophyll reaction centres can occur due to excess energy (Dai et al., 2009). In prolonged exposure, plants may not be able to efficiently dissipate this energy. Thus, the significant differences between covered and uncovered conditions in the present study are consistent with this mechanism, supporting the positive relationship observed between leaf chl indices, leaf area, and higher photosynthetic rates in covered vines (Chavarria et al., 2012).

4. Anatomical analyses

Anatomical analyses revealed that the palisade parenchyma, spongy parenchyma, and adaxial epidermis were more developed in covered leaves during most experimental cycles compared with uncovered leaves (Table 1). Raphides, needle-shaped crystals, were frequently observed in uncovered vines (Figure 10). These anatomical differences are likely influenced by light intensity.

Interestingly, the leaf anatomy of covered vines resembled the typical characteristics of shade leaves, such as thinner leaf blades with reduced palisade tissue and higher pigment accumulation (Zhang et al., 2022). Thinner leaves are known to enhance light interception compared to thicker ones (Terashima et al., 2011). This pattern was consistent with the findings of this study, where covered leaves were larger, had smaller palisade parenchyma, and exhibited higher chlorophyll indices. In contrast, uncovered leaves likely adjusted their structure in response to excessive light and lack of protection, thereby minimising damage to the photosynthetic apparatus. Under such conditions, leaves typically develop a thicker palisade parenchyma, sometimes with additional cell layers or elongated cells (Poorter et al., 2019), which aligns with the observations recorded in this study (Figure 10).

Table 1. Leaf anatomical characteristics of cv. Sauvignon blanc cultivated under plastic (covered) and outdoors (uncovered), in a double-pruning system across four different cycles.

Leaf anatomical characteristics	Winter (2022)				Summer (2023)
	Covered		Uncovered		Covered		Uncovered
Mesophyll (μm)	102.83 (± 9)	a	109.35 (± 7.54)	a	107.11 (± 6.22)	b	131.14 (± 7.03)	a
Adaxial epidermis (μm)	131.51 (± 0.85)	b	15.64 (± 1.56)	a	13.67 (± 1.83)	b	15.90 (± 1.45)	a
Palisade parenchyma (μm)	45.15 (± 6.44)	b	55.93 (± 4.97)	a	44.16 (± 2.64)	b	58.62 (± 5.78)	a
Spongy parenchyma (μm)	60.22 (± 6.25)	a	54.15 (± 7.25)	a	62.04 (± 6.83)	b	70.61 (± 4.53)	a
Stomatal density (stomata/mm2)	113.73 (± 9.21)	b	174.8 (± 11.4)	a	147.40 (± 4.20)	b	168.70 (± 8.27)	a
	Winter (2023)				Summer (2024)
	Covered		Uncovered		Covered		Uncovered
Mesophyll (μm)	98.81 (± 2.78)	b	104.57 (± 4.55)	a	105.60 (± 13.5)	b	122.68 (± 4.04)	a
Adaxial epidermis (μm)	10.36 (± 0.81)	b	13.76 (± 0.63)	a	10.56 (± 1.36)	b	14.74 (± 1.33)	a
Palisade parenchyma (μm)	40.94 (± 2.46)	b	48.03 (± 0.61)	a	47.26 (± 3.39)	b	53.69 (± 3.11)	a
Spongy parenchyma (μm)	50.17 (± 2.52)	b	55.50 (± 4.38)	a	57.5 (± 11.7)	b	69.97 (± 4.54)	a
Stomatal density (stomata/mm2)	128.67 (± 4.55)	b	152.50 (± 10.9)	a	122.2 (± 13.2)	a	128.3 (± 11.5)	a
Cuticle (μm)	—		—		1.24 (± 0.11)	a	1.18 (± 0.17)	b

Means followed by the same letter in the row, in each cycle, indicate no significant difference among them according to the t-test (p < 0.05).

Stomatal density (SD), defined as the number of stomata per square millimetre of leaf surface, varied significantly across all cycles except for cycle 4, with uncovered vines consistently showing higher SD. Scanning electron microscopy analysis of the abaxial epidermis further revealed that uncovered leaves had a greater deposition of epicuticular wax on the ordinary epidermal cells and guard-cells in the form of platelets (Figure 11).

The micromorphology of the grapevine leaf cuticles of the covered and uncovered plants shows a plasticity pattern of the epicuticular wax production. The epicuticular wax plays a key role in reducing UV damage, non-stomatal dehydration, the effect of strong sunlight, and preventing fungal invasion (Guo et al., 2011; Marques et al., 2016; Guan et al., 2024). The effect of light on epicuticular wax micromorphology was investigated in Hosta spp. genotypes, indicating that higher light intensities modify wax crystal organisation and are associated with changes in cuticular structure (Guan et al., 2024). Similar results were observed herein, showing that direct light exposition alters cuticle micro morphology and its protection may prevent epicuticular wax changes. SD is strongly influenced by environmental factors affecting both developing and mature leaves. For example, when mature leaves are exposed to shade or elevated CO₂ levels, newly emerging leaves typically develop a reduced SD (Engineer et al., 2016; Lake et al., 2001).

Despite these findings, the role of SD in photosynthesis and plant growth remains controversial. Some studies have shown that reduced SD can promote greater plant height and biomass under constant light and favourable water and temperature conditions, as stomatal development requires considerable energy (Wang et al., 2016). Conversely, other studies have reported that lower SD is associated with reduced photosynthetic rate and stomatal conductance (Lawson & Blatt, 2014). In this study, the higher SD observed in uncovered vines was not sufficient to enhance the photosynthetic rate, most likely due to the unfavourable conditions these plants experienced, such as elevated temperatures, excess light, and increased disease incidence.

5. Chemical control

The plastic covering prevented the direct incidence of rainwater on the leaves of covered vines, thereby reducing the wash-off of applied chemicals such as fungicides and insecticides. As a result, the frequency of pesticide application differed between treatments. Across all cycles, only two sprayings were required in the covered system, whereas in the uncovered system, the number varied between 7 and  0, depending on the cycle (Table 2). Consequently, protected cultivation reduced both the number of chemical applications and the incidence of diseases. Interestingly, caterpillar attacks were observed only in uncovered rows. These findings reinforce that management strategies that modify environmental conditions represent an effective approach to disease control by creating environments less favourable to pathogens.

Table 2. Number of sprayings during the cycle in cv. Sauvignon blanc vines conducted under covered and uncovered conditions.

Cycles	Number of sprayings Covered	Number of sprayings Uncovered
Winter (2022)	2	7
Summer (2023)	2	10
Winter (2023)	2	7
Summer (2024)	2	9

Other studies have also reported differences in chemical control strategies in vineyards due to plastic covering. For instance, Chavarria et al. (2007) recorded 17 pesticide applications in uncovered vineyards compared to only 2 in covered vineyards. Similarly, Genta et al. (2010) reported a 75 % reduction in pesticide spraying under protected cultivation. Taken together, these results indicate that the use of plastic covering is an effective strategy for disease management, mitigating the challenges posed by unfavourable weather conditions.

Conclusion

The use of plastic covering created a favourable microclimate that positively influenced vine growth and development, while also reducing disease incidence. In the studied region of Brazil, the double-pruning management technique alone was insufficient, as it likely required multiple fungicide applications to maintain vine health. Plastic covering reduced PPFD levels to values sufficient for vines to reach light saturation, while simultaneously decreasing UV-B radiation. Together, these effects contributed to improved physiological processes, such as photosynthesis.