Early Leaf Removal Research Articles

Optimizing ‘Xinomavro’ (Vitis vinifera L.) Performance by Post-Bloom Basal Leaf Removal Applications

A three-year study was conducted to investigate the effects of two timings—at berry set and at veraison—of post-bloom leaf removal (LR) applications from the basal sections of the shoot on the growth, yield, and berry composition of Vitis vinifera L. cv. Xinomavro, the major red winegrape of North Greece. LR at berry set drastically reduced yield by affecting all its components while increasing the ratio of secondary foliage per total leaf area. LR at veraison had a milder effect on growth and yield. Both treatments increased sugar and phenolic compound levels in berries, while early LR increased the contribution of more stable forms of anthocyanins. Additionally, early LR increased the skin-to-pulp ratio, suggesting that it could be an effective viticultural technique for more concentrated red wines. Overall, both LR timings improved most of the berry attributes compared to the non-treated vines; however, the earlier application can be recommended when aiming at the production of deep-colored and richly flavored wines.

Timing of leaf removal modulates tannin composition and the level of anthocyanins and methoxypyrazines in Pinot noir grapes and wines

This study aimed to investigate the impact of leaf removal on concentrations of anthocyanin, tannin, and methoxypyrazines (MPs) in Pinot noir grapes and wines. Leaf removal after 7 days (LR7), 30 days (LR30), and 60 days (LR60) of flowering were compared with no leaf removal control (LRC). Grapes and resultant wines were analysed for tannin and aroma composition using liquid chromatography and two-dimensional gas chromatography–mass spectrometry. All leaf removal treatments increased anthocyanin concentration in grapes and reduced MP levels in grape stems compared to LRC, indicating the effectiveness of both early and late leaf removal. Leaf removal after 7 days and 30 days were more effective in enhancing colour density, polymeric pigments, and tannin concentration in wines. Higher grape skin tannin and anthocyanin concentrations, along with lower seed tannin concentration in berries, correlated with higher tannin concentrations in wines. LR7 showed significantly higher skin-originated tannin proportion than LRC, suggesting a useful tool to manage tannin extraction. Aroma composition of resultant wines was influenced by leaf removal, although these differences were not evident in the sensory evaluation.

Identifying an Early Leaf Removal Threshold for Grüner Veltliner, a High-Yielding, High-Vigor Cultivar

Identifying an Early Leaf Removal Threshold for Grüner Veltliner, a High-Yielding, High-Vigor Cultivar

Evaluating the Effects of Early Pruning, Leaf Removal, and Shoot Thinning on ‘MidSouth’ Grapes over Two Consecutive Vintages in South Mississippi

Yield components and fruit composition of ‘MidSouth’, an interspecific hybrid bunch grape (Vitis spp.) with relatively low total soluble solids and high titratable acidity, was evaluated in south Mississippi to determine if treatments consisting of early pruning, early pruning with pre-bloom leaf removal, normal pruning with post-fruit set leaf removal, or normal pruning in one study, or post-fruit set leaf removal, post-fruit set shoot thinning, or neither leaf removal nor shoot thinning in a second study could improve these qualities. Early pruning with leaf removal reduced berries per cluster, cluster weights, yields, and Ravaz index. Early pruning treatments had inconsistent results from year to year, and normal pruning treatments were not often significantly different. Shoot thinned vines had lower yields and Ravaz index and higher total soluble solids. Second study leaf removal vines had lower juice pH in 2020 and lower yield per vine in 2021. These findings show that ‘MidSouth’ can be altered by these practices, but they did not appear to sufficiently alter ‘MidSouth’ quality. Thus, early pruning with or without leaf removal, normal pruning with leaf removal, and shoot thinning are not recommended for ‘MidSouth’ in south Mississippi, and normal pruning without these practices should be continued.

Early Basal Leaf Removal at Different Sides of the Canopy Improves the Quality of Aglianico Wine.

It is well known that the early removal of basal leaves is a viticultural practice adopted to improve the exposure of clusters to direct sunlight and UV radiation and increase the phenolic compounds and anthocyanin concentration in the berries. The aim of this work was to study the influence of early basal leaf removal on Aglianico wines produced in the Apulia region (southern Italy) during three consecutive seasons. Three vine treatments were carried out, where 100% of the cluster-zone leaves on the north, south and both sides of the canopy were removed. Undefoliated plants were used as a control. The effect of the treatments on the basic chemical parameters, phenol content and volatile composition of wines was investigated using WineScan FT-MIR, spectrophotometry, HPLC-DAD and SPME-GC/MS. Early defoliation increased the amounts of flavonoids (+35–40%), anthocyanins (+15–18%), total polyphenols (+10%), antioxidant activity (+8–14%) and colour intensity (+10%), especially when leaf removal was applied on the south side. Moreover, leaf removal led to a 40% increase in free anthocyanins when applied on the south side of the canopy, while a 24% increase was observed when applied to the north side and 21% when applied to the north and south sides. A negative effect was observed on volatile compounds, which decreased by about 18, 14 and 13% when the treatment was applied on the north, north-south and south sides of the canopy, respectively. In conclusion, early leaf removal treatments allow for the modulation of the phenolic and volatile concentrations of Aglianico wines.

Effect of Early Basal Leaf Removal on Phenolic and Volatile Composition and Sensory Properties of Aglianico Red Wines.

The aim of this work was to study the influence of early basal leaf removal on Aglianico wines produced in the Apulia region (Italy). Three treatments were carried out, where 100% of fruit-zone leaves on the north (DN), south (DS) and on both sides of the canopy (DNS) were removed. A control (CT), where all basal leaves were retained, was also performed. Instrumental (HPLC-DAD-MS and GC-MS) and sensory analysis (QDA) were used to evaluate the treatment effect on the phenolic and volatile compositions and on the sensory descriptors of wines. DNS reached the highest amounts of phenolic compounds, showing a change in the phenolic pattern from flavonols and anthocyanins. Moreover, leaf removal influenced the levels of 37.8% of volatile compounds, quantified by increasing the concentration when early leaf removal was applied on the north side of the canopy (DN), with respect to the south (DS) and both sides (DNS). In the sensory analysis, Aglianico wines were defined by 16 sensory attributes with GM > 30%, where the highest values were reached for defoliation treatments vs. control. In conclusion, early leaf removal treatments allowed us to modulate the phenolic and volatile concentrations of Aglianico wines.

Cluster-Zone Leaf Removal and GA3 Application at Early Flowering Reduce Bunch Compactness and Yield per Vine in Vitis vinifera cv. Pinot Gris

Compact bunches have been often associated with higher susceptibility to Botrytis cinerea and therefore reduction in berry quality in grapevine. The objective of this study was to evaluate three management methods (early leaf removal, gibberellic acid, and their combination) for reducing bunch compactness in Vitis vinifera cv. Pinot gris trained in two different training systems with contrasting vigor (Guyot and pergola). Treatments were applied at BBCH 62 or BBCH 65 and yield components, total soluble solids, fruit set, and bunch compactness parameters were evaluated. Both treatments individually reduced berry number, mean bunches weight and bunches compactness as well as yield per vine when compared to control-untreated vines. However, no major differences were observed when both the treatments were applied in combination for Guyot or pergola although a higher reduction in yield was detected for Guyot and a significant increase in total soluble solids was observed in pergola. Our study suggests that intense leaf removal and gibberellic acid applied at early flowering can help reducing bunch compactness in Pinot gris and showing it in two training systems. In particular, leaf removal represents a valuable alternative to plant growth regulators (i.e., gibberellic acid) as applicable in organic viticulture.

Impact of canopy management practices on phenolic composition and sensory profile of cv. Teran wine

The aim of this study was to investigate the impact of early leaf removal (ELR) and cluster thinning (CT) on the phenolic composition of cv. Teran berries and wines, and the sensory profile of wines at 6 and 24 months after fermentation. Although only ELR increased the concentration of total anthocyanins in the berries as compared to the untreated control (UC), both ELR and CT had higher concentration of total anthocyanins and greater colour intensity in the resultant wines than the UC. Similar effects were obtained with total phenolics in the berries and the wines; while CT obtained higher concentration of total phenolics in the berries than UC only in one season, same treatment obtained higher concentration of total phenolics in the wine in both seasons as compared to UC. Only minor sensory differences in wines were obtained at the age of 6 months, while treatments were highly discriminated 24 months after fermentation, when both ELR and CT wines had more enhanced fruitiness, aromatic intensity, complexity, body, balance and wine overall quality than UC. The obtained results indicate that adequate wine aging period is needed for a relevant assessment of the impact of vineyard management practices on wine sensory characteristics.

Performance of Early Fruit-Zone Leaf Removal in Cabernet Sauvignon and Merlot in an Arid Climate

<h3>Summary</h3> <h3>Goals:</h3> Our goals were to evaluate how the timing of early fruit-zone leaf removal, done between prebloom and post-fruit set, influenced the risk of reduced fruit set, sunburn, and fruit quality in <i>Vitis vinifera</i> Cabernet Sauvignon and Merlot grown in the hot, arid, and irrigated region of eastern Washington State. <h3>Key Findings:</h3> Fruit set was reduced in <i>V. vinifera</i> Cabernet Sauvignon when fruit-zone leaf removal was completed during bloom. Prebloom and postbloom fruit-zone leaf removal did not reduce fruit set. Sunburn occurred on fruit on the westside of the canopy in both <i>V. vinifera</i> Cabernet Sauvignon and Merlot. Sunburn severity increased with later-timed fruit-zone leaf removal. Overall, the maximum severity of sunburn was 15% of the cluster surface area. Vintage had a greater effect on fruit quality than timing of leaf removal for both varieties. This emphasizes the need to make canopy management decisions that are informed by weather forecasts to achieve desired management goals. <h3>Impact and Significance:</h3> Early fruit-zone leaf removal was traditionally avoided in eastern Washington, in favor of completing the practice after berries have reached pea-size. The later timing of leaf removal, however, can result in sudden exposure of the fruit during the typically warmest and sunniest time of the growing season. Results from this study show that many of the assumed risks associated with early fruit-zone leaf removal, such as extreme reduction in fruit set and sunburn, are not fully realized. This means that early fruit-zone leaf removal could be adopted in this hot, arid climate without a high risk of reduction in fruit quantity or quality.

EARLY LEAF REMOVAL AS STRATEGY TO REDUCE BOTRYTIS BUNCH ROT ON CHARDONNAY GRAPEVINE IN HIGH ALTITUDE REGION OF SANTA CATARINA STATE

The objective of this work is to compare different periods of leaf removal in the control of this disease in Chardonnay grown in high altitude regions of Santa Catarina - Brazil. The experiments were conducted in São Joaquim city, in 2018 and 2019 growing seasons. The treatments consisted of leaf removal at the phenological stages of full bloom, buckshot berries, pea-sized berries, veraison, and the control treatment, in which the plants without leaf removal. Epidemiological variables were calculated from: beginning of symptom appearance; times to reach maximum disease incidence and severity; maximum disease incidence and severity; and areas under the incidence and severity disease progress curves. The results of the present work show the importance of early leaf removal of Chardonnay in management of B. cinerea, it is recommended to be carried out at the phenological stages of full bloom, buckshot berries and pea-sized berries, as it provides a reduction in the maximum severity of B. cinerea and a reduction of AUSDPC. The rate of disease progression demonstrated that B. cinerea infection and development was faster in plants not submitted to leaf removal. The management of early leaf removal is efficient to prevent the development of B. cinerea in Chardonnay.

Early Defoliation Impact on Fruitset, Yield, Fruit Quality, and Cold Hardiness in ‘Chambourcin’ Grapevines

Several winegrape cultivars grown in cool climates, including Vitis sp. ‘Chambourcin’, are highly productive and require crop regulation to ensure timely fruit maturation and improved fruit quality. Balanced pruning and cluster thinning are the cultural practices used to attain the desired crop load in ‘Chambourcin’. However, crop reduction by cluster thinning is labor intensive, costly and typically not mechanized for winegrapes. In this study, the practice of early season leaf removal was investigated as an alternate tool to reduce crop level, thereby optimizing crop load and fruit quality in ‘Chambourcin’. The specific objectives were to determine the effects of the timing of leaf removal (pre-bloom, bloom, fruitset, no removal) on yield components, crop load, fruit composition, and cold hardiness. Leaf removal at pre-bloom and bloom reduced yield and crop load (Ravaz index) as compared to control (no defoliation). However, leaf removal did not impact fruit composition. Furthermore, defoliation at pre-bloom and bloom reduced bud cold injury during the dormant season. Therefore, early season leaf removal is a viable alternative to cluster thinning as a vineyard practice for yield regulation in ‘Chambourcin’ grapevines.

Phenolic profile of grapevine cv. Tempranillo skins is affected by timing and severity of early defoliation

Aim of study: To investigate the effects of three early leaf removal treatments on the phenolic compounds of cv. ‘Tempranillo’ (Vitis vinifera L.) grape skins.Area of study: The experiment was conducted in a vineyard located in Requena, Valencia (South-eastern Spain) over two consecutive seasons.Materials and methods: Four treatments were investigated over two seasons in drip-irrigated vines: Control (C), non-defoliated and three defoliation treatment, applied at different phenological stages and intensities where all leaves from the first 6 nodes were eliminated just before flowering (ED) and at fruitset (LD). The fourth defoliation treatment was performed at the same time of ED but only the leaves facing east of the eight first nodes were removed (EED). At harvest, thirty-eight phenolic compounds were quantified by HPLC in the grape skins, including anthocyanins, flavanols, flavonols, hydroxycinnamic acids and their tartaric derivatives.Main results: A general increase of the skin phenolic compounds concentration was found in response to the defoliation treatments. The largest and more significant effects were observed for LD in 2009 with relative increases with respect to the un-defoliated vines of 14.8, 86.0, 119.0, and 75.9% for anthocyanins, flavanols, flavonols and hydroxycinnamates, respectively. On the other hand, EED did not clearly modify any polyphenolic compound. In addition, the response of phenolic families analyzed to defoliation treatments was different. Malvidine derivatives were not altered by any of the treatments, while the contents of quercetin and kaempferol derivatives and ferulic and coumaric acids, increased in both years when LD was applied.Research highlights: The defoliation effects on specific phenolic substances were dependent on timing, severity, and the season. Skin phenolic compounds increase in response to defoliation treatments and flavonols and hydroxycinnamates were the most affected families.

Mid-Term Effects of Conservative Soil Management and Fruit-Zone Early Leaf Removal Treatments on the Performance of Nerello Mascalese (Vitis vinifera L.) Grapes on Mount Etna (Southern Italy)

The aim of this study was to analyze the mid-term influence of minimum tillage (MT) combined with early leaf removal (ELR) on the performance of the black grapevine variety Nerello Mascalese (Vitis vinifera L.). The research was carried out from 2015 to 2018 in a vineyard located in the Mount Etna area, East Sicily, Southern Italy. An average of about 8000 cm2 of leaves were removed from the ELR vines, corresponding to a canopy defoliation of 44% in 2017 and 30% in 2018. As for the stem water potential of both primary and lateral leaves, ELR-MT treatment showed the best performance (up to −0.4 MPa) among the four combinations. In 2017, no differences in yield/vine were found among treatments, whereas in 2018 the yield was significantly lower in ELR treatments. Among the different treatments performed, the ELR-MT showed the best results both in terms of physiological plant parameters (water status and photosynthetic activity) and fruit quality (higher concentration of sugars and total anthocyanins and polyphenols). ELR-MT treatment is also associated with a lower incidence of tillage operations from four to only one per year (−60–70 h/ha). In contrast to what was observed in the first 3 years of application (i.e., from 2015 to 2017), yield was heavily penalized during the fourth year of application (2018), probably due to the excessive depletion of nutritional reserves, the reduction of bud fertility and the unfavorable meteorological condition. For these reasons, the ELR-MT combination might require an interruption every 2–3 years of application.

Impacts of Pre-bloom Leaf Removal on Wine Grape Production and Quality Parameters: A Systematic Review and Meta-Analysis

Wine grape (Vitis vinifera L.) is the most widely cultivated fruit crop in the world. However, the climactic characteristics in some growing regions are suboptimal for grape production, including short season length and excess precipitation. Grape growers can utilize an array of methods to mitigate these issues, including “early leaf removal,” a management practice involving the removal of leaves from selected basal nodes along shoots around bloom. This meta-analysis reviews the extensive literature on this practice, with specific regards to application at “pre-bloom” (PB). One hundred seventy-five publications on the topic of “early leaf removal” were identified using key terms and subsequently narrowed via eight data curation steps. The comparison between treated (PB) and control plants in these studies revealed two important results. First, PB lowered bunch rot disease (−61%), partially through reducing the compactness of clusters. Second, PB promoted a significant increase in fruit total soluble solids (°Brix, +5.2%), which was related to the increase in the leaf-to-fruit ratio. Furthermore, cultivar and rootstock were found to have a large influence on the success of PB, while the contribution of climate was smaller. In conclusion, PB significantly lowers yield and bunch rot disease and increases °Brix, both of which improve grape and wine quality.

Early Leaf Removal Increases Berry and Wine Phenolics in Cabernet Sauvignon Grown in Eastern Serbia

Cluster zone leaf removal is a well-established viticulture practice for improving cluster microclimate and wine quality in cooler climates, while its efficacy in warmer conditions is less is known. Here we compared the effect of early (ELR, after fruit set; diameter of berries 3–5 mm) and late (LLR, beginning of veraison) leaf removal on berry composition and wine phenolic profile of grapevine (Vitis vinifera L.) variety Cabernet Sauvignon grown in a temperate, warmer region of Eastern Serbia. Compared to the control (no leaf removal), both leaf removal treatments increased the sugar content in fresh juice and alcohol concentration in wine. Over three consecutive years (2011–2013) markedly different in temperature and rainfall, ELR was clearly most effective in decreasing weights of cluster and of one berry, and in increasing of skin share in a berry. The content of total phenols, tartaric acid esters, anthocyanins, and flavanols in berry skin and wine was the highest in ELR treatment. ELR prominently modified the phenolic profile: Increasing flavanols, myricetin and quercetine in skin and wine, and anthocyanins, peonidin-3-glucoside in skin and delphinidin-3-glucoside in wine. This work demonstrated that early leaf removal positively influenced the chemical composition of berries and wine of Cabernet Sauvignon and might be recommended for practice in the temperate warm conditions.

The Impact of Early Basal Leaf Removal at Different Sides of the Canopy on Aglianico Grape Quality

It is known that early removal of basal leaves improves the exposure of cluster to direct sunlight and UV radiation, which positively influence the phenolic compounds and anthocyanin concentration of berries. This study was carried out to evaluate the effect of leaf removal applied before flowering to the basal zone of the canopy at different sides (fruit-zone north canopy side, south canopy side and north–south canopy side, respectively) of Aglianico vines trained to vertical shoot position system and row oriented to east–west (EW). The study was conducted in the controlled and guaranteed designation of origin (CGDO) Castel del Monte area (Apulia region, Italy). The treatment did not affect yield per vine, and nor sugar, pH, and total acidity of grapes. When it was applied to the basal south canopy side, the concentration of proanthocyanidins and total polyphenols of grapes increased, as well as antioxidant activity. In particular, anthocyanins content, determined by HPLC, increased by 20% with respect to control when treatment was applied to south and north–south canopy sides. Interaction between season period and treatment was found for all anthocyanins except for petunidin-3-coumaroyl-glucoside. Basal leaf removal applied to the north canopy side caused an increase in malvidin-3-O-glucoside content in grapes in 2016 and 2018, but not in 2017. Our results indicate that basal leaf removal (six basal leaves removed from the base of the shoots) before flowering (BBCH 57) can be used as an effective strategy to improve grape total polyphenols, anthocyanins concentration and antioxidant activity in vineyards cultivated under warm climate conditions. The treatment could represent a sustainable alternative to manual cluster thinning since it does not reduce yield per vine and can be performed mechanically.

Canopy architecture and fruit microclimate, not ripening-related phytohormones, control phenylpropanoid accumulation in response to early leaf removal in ‘Merlot’ (Vitis vinifera L.) grapevines

Early leaf removal (ELR) applied in the grapevine cluster zone at bloom or pre-bloom (PB) is a vineyard practice commonly utilized to reduce fruit disease and yield. In addition, the literature reports that ELR enhances fruit quality, however, little research has deciphered the potential factors regulating this response. In this work, the objective was to understand whether the increase in fruit quality in response to manual or mechanical leaf removal is due to changes in fruit-zone microclimate, vine physiology, or ripening/stress related hormone biosynthesis. In ‘Merlot’ (Vitis vinifera L.) vines, 60% of leaf area was removed from shoots in three ways: 1) manual removal of 5 leaves (PB-MA), 2) mechanical removal (PB-ME), and 3) simulated mechanical removal (PB-SIM), which was implemented by removing the distal portion of leaves on the first eight nodes to understand whether PB-ME improves fruit quality via enhanced microclimate conditions or plant stress. Yield was reduced in PB-ME and PB-SIM, while total soluble solids was not different at harvest; meaning that ELR decreased the partitioning of carbohydrates to fruit. Anthocyanins and flavonols were enhanced by PB-ME, however neither ABA nor ethylene were similarly altered. Instead, the leaf area at nodes above the fruit-zone was lower in PB-ME compared to non-defoliated ones, which increased post-veraison fruit temperature (+2.8 °C). These parameters correlated with anthocyanins at harvest. In conclusion, skin phenylpropanoid concentrations were influenced by canopy density above the fruit-zone. Additionally, ripening-related phytohormones were not involved in the response of phenylpropanoid biosynthesis in vine subjected to ELR.

The impact of cluster thinning and leaf removal timing on the grape quality and concentration of monomeric anthocyanins in Cabernet-Sauvignon and Probus (Vitis vinifera L.) wines

Aim: Leaf removal around clusters and cluster thinning are techniques usually applied in cool-climate vineyards in order to achieve optimal grape maturity. However, the impact of the timing of these two operations differs across varieties. Thus, the aim of the present work was to investigate the effects of cluster thinning and leaf removal timing (performed at three specific time points) on grape quality and monomeric anthocyanins in the wines of Cabernet-Sauvignon and Probus (Kadarka × Cabernet-Sauvignon, Vitis vinifera L.)Methods and results: The experiment was conducted in Sremski Karlovci (Northern Serbia) in 2014, 2015, and 2016. Leaf removal was applied on six basal nodes of each shoot at three time points, 7 days after flowering, 30 days after flowering, and at veraison, i.e., at the onset of berry ripening. After cluster thinning, which was performed 7 days after flowering, one cluster per shoot was retained. On the treated vines, leaf removal treatment and cluster thinning were applied only once. Leaf removal was more effective than cluster thinning in respect to grape quality. Leaf removal, applied 7 and 30 days after flowering, decreased titratable acidity in Cabernet-Sauvignon, while in Probus an interaction of leaf removal and year was observed. Moreover, early leaf removal decreased the incidence of Botrytis sp. in Probus. The varieties reacted differently to cluster thinning in respect to grape quality: cluster thinning increased total soluble solids in Probus and lowered titratable acidity in Cabernet-Sauvignon. In 2015, both cluster thinning and leaf removal yielded changes in the anthocyanin ratios in the wines. Cluster thinning increased total and acylated anthocyanins in the wine of Cabernet-Sauvignon compared to wine derived from unthinned vines. The peonidin content was 40 % higher in the Cabernet-Sauvignon wine if the vines were subjected to leaf removal treatments.Conclusions: Cluster thinning and leaf removal affected both Cabernet-Sauvignon and Probus (Vitis vinifera L.) grape quality and wine composition. Early leaf removal was the most effective treatment in both varieties. Therefore, combined application of cluster thinning and early leaf removal is highly recommended in the production of high-quality red wines in Serbia.Significance and impact of the study: Timing of leaf removal application was usually investigated around flowering and veraison. Our results suggested that leaf removal between these two phenological stages also improves grape quality and changes the ratio of the monomeric anthocyanins in the wine.

Effect of cluster zone leaf removal on monoterpene profiles of Sauvignon Blanc grapes and wines

Monoterpenes contribute to the varietal aromas of grapes and wines. We determined the effects of cluster zone leaf removal on the monoterpene profiles of Sauvignon Blanc grape berries and wines, and on the expression of key genes in the terpenoid pathway. Leaf removal at two intensities (half basic, 50%; full basic, 100%) was conducted at two weeks before veraison, veraison, and two weeks after veraison. Half basic leaf removal increased the pH and decreased the tartaric acid content in grapes and wines. The concentrations of most free- and bound-form monoterpenes in grapes were increased by early leaf removal. The total monoterpene contents were increased in wines in the defoliation treatments, but were significantly lower in wines from the full basic leaf removal treatments than in wines from the half basic leaf removal treatments. The defoliation treatments resulted in increased transcript levels of some key genes in terpene biosynthesis (VvPNLinNer1, VvPNLinNer2, VvPNLNGl1, VvPNLNGl2, and VvUGT88A1L1).

Effects of leaf removal on grape cluster architecture and control of Botrytis bunch rot in Sauvignon Blanc grapevines in Southern Brazil

Management practices, such as leaf removal, can affect grape cluster architecture and the microclimate around the cluster, which influences the development of Botrytis bunch rot disease. The timing of leaf removal among five different phenological stages was investigated as a tool for managing grape cluster architecture-related variables and for managing Botrytis bunch rot of Sauvignon Blanc grapevines. A commercial vineyard located in São Joaquim municipality, in the highland region of Santa Catarina State, Southern Brazil, was assessed in a randomized complete block design during the 2015 and 2016 growing seasons. The treatments consisted of leaf removal of four basal leaves around clusters at the phenological stages of full bloom, buckshot berries, pea-sized berries, veraison, and 15 days after veraison. At harvest, cluster architecture variables (cluster length, cluster mass, rachis mass, number of berries, berry mass, and cluster compactness index) and Botrytis bunch rot incidence and severity were assessed weekly from the first appearance of symptoms to harvest. Disease progress curves were constructed and compared to several epidemiological parameters. There was no significant effect of the removal of four basal leaves on the cluster architecture-related variables (cluster and berry masses, number of berries, and cluster compactness index); however, reduced the intensity of Botrytis bunch rot. Leaf removal carried out before veraison significantly reduced (P < 0.05) the incidence, severity, AUDIPC, and AUDSPC of Botrytis cinerea in Sauvignon Blanc when compared with those of vines without leaf removal. Early leaf removal at the phenological stages of full bloom, buckshot berries, and pea-sized berries reduced the severity of B. cinerea infection and showed in the phenological stage of full bloom the lowest values for AUDSPC of 199.26 and 171.30 in the 2015 and 2016 growing seasons, respectively. The results of this study suggest that leaf removal carried out before veraison during the phenological stages of full bloom, buckshot berries, or pea-sized berries should be recommended for Sauvignon Blanc cultivar production to reduce Botrytis bunch rot in the highland regions of Santa Catarina State, Southern Brazil.