Unsprayed Vines Research Articles

Uncovering the effects of kaolin on balancing berry phytohormones and quality attributes of Vitis vinifera grown in warm-temperate climate regions.

The application of kaolin particle film is considered a short-term strategy against several environmental stresses in areas with a Mediterranean-like climate. However, it is known that temperature fluctuations and water availability over the season can jeopardize kaolin efficiency in many Mediterranean crops. Hence, this study aims to evaluate the effects of kaolin foliar application on berry phytohormones, antioxidant defence, and oenological parameters at veraison and harvest stages of Touriga-Franca (TF) and Touriga-Nacional (TN) grapevines in two growing seasons (2017 and 2018). The 2017 growing season was considered the driest (-147.1 dryness index) and the warmest (2705 °C growing degree days) of the study. In 2017, TF kaolin-treated berries showed lower salicylic acid (-26.6% compared with unsprayed vines) and abscisic acid (ABA) (-10.5%) accumulation at veraison, whereas salicylic acid increased up to 28.8% at harvest. In a less hot season, TN and TF kaolin-treated grapevines showed a twofold in ABA content and a threefold increase in the indole-3-acetic acid content at veraison and lower ABA levels (83.8%) compared with unsprayed vines at harvest. Treated berries showed a decreased sugar content, without compromising malic and tartaric acid levels, and reactive oxygen species accumulation throughout berry ripening. The results suggest kaolin exerts a delaying effect in triggering ripening-related processes under severe summer stress conditions. Treated berries responded with improved antioxidant defence and phytohormone balance, showing significant interactions between kaolin treatment, variety, and developmental stage in both assessed years. © 2021 Society of Chemical Industry.

The effects of calcite silicon-mediated particle film application on leaf temperature and grape composition of Merlot (<i>Vitis vinifera L.</i>) vines under different irrigation conditions

Aim: This study examined whether the application of calcite-silicon mediated particle film (CaPF) at veraison can mitigate a drought-induced increase in leaf temperature on grapevine, thus contributing to improved leaf functionality, yield and grape composition traits.Methods and results: A total of 48 five-year-old Merlot (Vitis vinifera L.) vines grafted onto SO4 were grown (in 20 L PVC pots) under Mediterranean conditions (Southern Italy). The vines were pruned to a single spur with 3 winter buds irrigated daily to 100 % field capacity, and fertilised weekly.At veraison and using a 2×2 factorial experimental design, the two main factors, thermoregulation and water, were imposed at two levels: spraying with a thermoregulation compound (CaPF) and no spraying (NS); irrigation (WW) and drought stress (D)). A group of 24 vines was subjected to a 15-day drought period by receiving, every day, 25 % (D) of the daily water consumption of WW vines. The other 24 vines continued to be fully irrigated on a daily basis (WW). Twelve vines per group were sprayed (WW+CaPF, D+CaPF) with calcite-silicon mediate (3 % V/V) at the beginning of drought imposition, the remaining 24 vines were not sprayed (WW-NS, D-NS). Soil water moisture and stem water potential values were monitored from 11.30 to 13:30 nearly every week, and other vegetative and reproductive parameters were also measured.During the experiment, air temperature peaked at ≈35°C at midday, VPD at about 3.7 kPa and PAR reached ≈2000 µmol m-2 s–1. Results show that in CaPF sprayed vines, leaf-air temperature differences were lower than in unsprayed vines in both irrigated and drought stressed groups. WW+CaPF vines retained significantly more leaf area and showed the highest value of accumulated vine transpiration.Conclusion: Calcite-silicon mediated particle film could enhance the resilience of grapevine to adverse environmental conditions and may contribute to preserve terroir elements in highly reputed wine grape growing areas.Significance of the study: The study showed that foliar application of calcite silicon-mediated processed particles films can be used in arid regions to mitigate leaf temperatures in grapevines.

Production and Release of Asexual Sporangia in Plasmopara viticola

To study the influence of environmental conditions on sporulation of Plasmopara viticola lesions under vineyard's conditions, unsprayed vines were inspected every second or third day and the numbers of sporulating and nonsporulating lesions were counted in two North Italy vineyards in 2008 to 2010. Infected leaves were removed so that only fresh lesions were assessed at each field assessment. Sporulation was studied at two scales, across field assessments and across the seasonal population of lesions. Frequencies of sporulating lesions were positively correlated with the numbers of moist hours in the preceding dark period (i.e., the number of hours between 8:00 p.m. and 7:00 a.m. with relative humidity ≥80%, rainfall >0 mm, or wetness duration >30 min). In a receiver operating characteristic analysis, predicted sporulation based on the occurrence of ≥3 moist hours at night provided overall accuracy of 0.85. To study the time course of sporulation on lesions which were not washed by rainfall, numbers of sporangia produced per square millimeter of lesion were estimated on individual cohorts of lesions over the whole infectious period. The numbers of sporangia per square millimeter of lesion increased rapidly during the first 4 days after the beginning of sporulation and then tapered off prior to a halt; the time course of cumulative sporangia production by a lesion followed a monomolecular growth model (R(2) = 0.97). The total number of sporangia produced by a square millimeter of lesion increased as the maximum temperature decreased and moist hours in the dark increased. To study the release pattern of the sporangia, spore samplers were placed near grapevines with sporulating lesions. Airborne sporangia were caught in 91.2% of the days over a wide range of weather conditions, including rainless periods. The results of this study provide quantitative information on production of P. viticola sporangia that may help refine epidemiological models used as decision aids in grape disease management programs.

Effect of Molybdenum Foliar Sprays on Yield, Berry Size, Seed Formation, and Petiolar Nutrient Composition of “Merlot” Grapevines

Field experiments with irrigated “Merlot” vines were carried out at 3 sites in the Mount Lofty Ranges of South Australia over 3 years to examine the effects of molybdenum (Mo) foliar sprays on bunch yield, berry size, and nutrient composition of petioles. Bunches were divided into different size grades for black and green berries. Basal petioles were sampled at flowering and veraison for nutrient analyses. In year 3, seed number per berry was assessed at sites 2 and 3. Two Mo foliar sprays (each spray contained 118 g Mo as sodium molybdate/ha in 410–800 L/ha of water) applied before flowering increased yield per vine and bunch weight in all experiments in year 2 and at site 3 in year 3. Yield responses ranged from 221% at site 1 to 750% at site 2 in year 2 and 70% for site 3, year 3. Average bunch weight increased from 243% at site 2 to 425% at site 1 for year 2 and by 69% at site 3 in year 3, and was the main yield component affected by Mo application. In year 1, the application of Mo did not affect yield or bunch weight at any site. In year 2, the application of Mo increased the yield of 5–15 mm colored berries by 301, 499, and 258% at sites 1, 2, and 3, respectively, and by 70% at site 3, year 3. Mo application increased the percent of berries, which had one or more functional seeds (when assessed at sites 2 and 3 in year 3). Molybdenum concentrations in petioles sampled at flowering and veraison increased in response to applied Mo in all years. Petiolar Mo concentrations in unsprayed vines were consistently higher in year 1 compared with other years. The effect of applied Mo on the concentration of other nutrients in basal petioles sampled at flowering and veraison were small and of little practical importance. Nitrate-N did not accumulate in the petioles of unsprayed plants in any year. Changes in petiolar Mo concentrations between flowering and veraison were dependent on supply. Nitrate-N, total-N, and phosphorus (P) concentrations declined with time, while calcium (Ca), manganese (Mn), and iron (Fe) tended to increase. At flowering, Mo concentrations in basal petioles of 0.05–0.09 mg/kg were associated with significant bunch yield response to applied Mo. Molybdenum deficiency can be a major factor in the occurrence of berry development disorders such as shot berry formation and hens and chickens (millerandage) in “Merlot” grapevines. The increased percent of colored berries with one or more functional seeds and the decrease in the proportion of green berries suggests that Mo application affected pollination and/or fertilization, and thereafter berry development.

Foliar Urea Application in the Fall Affects Both Nitrogen and Carbon Storage in Young `Concord' Grapevines Grown under a Wide Range of Nitrogen Supply

One-year-old `Concord' grapevines (Vitis labruscana Bailey) were fertigated with 0, 5, 10, 15, or 20 mm N in a modified Hoagland's solution for 8 weeks during summer. Half of the vines fertigated at each N concentration were sprayed with 3% foliar urea twice in late September while the rest served as controls. Four vines from each treatment combination were destructively sampled during dormancy to determine the levels and forms of N and carbohydrates. Nitrogen fertigation during the summer did not significantly alter vine N concentration whereas foliar urea application in the fall significantly increased vine N concentration. In response to foliar urea application, concentrations of both free amino acid-N and protein-N increased, but the ratio of protein-N to free amino acid-N decreased. Arginine was the most abundant amino acid in free amino acids and proteins, and its concentration was linearly correlated with vine N concentration. Concentrations of total nonstructural carbohydrates (TNC) decreased slightly in response to N supply from fertigation. Foliar urea application in the fall significantly decreased TNC concentration at each N fertigation level. Starch, glucose, and fructose decreased in response to foliar urea applications, but sucrose concentration remained unaffected. Approximately 60% of the carbon decrease in TNC caused by foliar urea application was recovered in proteins and free amino acids. We conclude that free amino acids account for a larger proportion of the N in vines sprayed with foliar urea compared with the unsprayed vines, but proteins remain as the main form of N storage. In response to foliar urea application, part of the carbon from TNC is incorporated into proteins and free amino acids, leading to a decrease in the carbon stored in TNC and an increase in the carbon stored in proteins and free amino acids.

Resveratrol Content of Muscadine Berries is Affected by Disease Control Spray Program

Control of muscadine diseases is necessary to minimize yield loss and is especially important for highest quality fresh-market berries. In a systematic disease control spray program, four fungicides registered for grapes were applied sequentially at 10- to 20-day intervals from early bloom until just before harvest to five muscadine cultivars. Objectives of the study were to: 1) determine the effects of the spray schedule on foliage and berry diseases; and 2) study the relationship between disease incidence and resveratrol content of the berries. Resveratrol, a phytoalexin, has shown potential value in prevention and treatment of cardiovascular disease and certain cancer processes. Foliar diseases were rated visually twice during the season. Berry disease ratings were made at harvest. All fungal foliage and berry diseases were significantly reduced by fungicide treatments. Resveratrol was determined separately on berry skins, seed and pulp/juice by gas chromatography/mass spectroscopy (GC/MS). Overall, resveratrol levels in berry skins from unsprayed vines were much higher than those of sprayed vines. Concentrations varied by cultivar and within cultivar by treatment. The relationship between resveratrol concentration in skins and total disease score or scores of specific diseases was not established. Seed resveratrol concentrations differed by cultivar but were not affected by the fungicide treatments. Resveratrol concentration of seed was lower than that of skins. Accumulation of resveratrol in juice/pulp was much lower than in skins and seeds.

Effects of Powdery Mildew on Vine Growth, Yield, and Quality of Concord Grapes.

Vitis labruscana 'Concord' is a widely planted grape cultivar grown in the United States for processing into juice and other products. Concord fruit are sporadically but sometimes severely damaged by the grape powdery mildew pathogen, Uncinula necator. The effects of powdery mildew on vine growth, yield, and quality of Concord grapes at three levels of cropping intensity commonly found in commercial grape production were determined in vineyard studies. Top-wire cordon-trained Concord vines were balance pruned, pruned to retain 80 nodes, or minimally pruned. Replicated plots of the foregoing were then either protected from powdery mildew by regular fungicide applications, or were inoculated and left unsprayed. Over a 4-year period, the effects of foliar infection on vine growth, yield, and juice quality of unsprayed vines were compared with vines that received a conventional protection program of four fungicide applications. Failure to control powdery mildew resulted in a chronic reduction in wood maturity measured as the number of nodes on canes that developed periderm. The reduction in nodes did not reduce yield, possibly due to compensation in shoots produced from the remaining nodes. Powdery mildew did not affect bud survival or vigor, measured as the number of shoots produced per node on retained canes. The most significant effects of powdery mildew were on berry sugar levels and juice color and acidity, which on the unsprayed vines were sometimes reduced below minimally acceptable thresholds for processed grapes. Significant reductions due to powdery mildew in these parameters occurred in all three pruning treatments, but were most pronounced at higher cropping levels.

019 Effect of Fungicidal Spray Program on Resveratrol Production of Muscadine Grapes (Vitis rotundifolia Michx.)

Control of muscadine diseases is necessary to minimize yield loss and is especially important for highest quality if the berries are to be marketed fresh. Throughout the 1998 growing season, vines of five muscadine cultivars (`Noble', `Summit', `Cowart', `Higgins', and `Carlos') were treated under a systematic disease control spray program; four fungicides registered for use on grapes were applied sequentially at 10- to 20-day intervals from early bloom until just before harvest. Control plants received no fungicide. The objectives of the study were to determine the effects of the spray schedule on foliage and berry diseases and to study the relationship between disease incidence and resveratrol content of the berries. Resveratrol is a phytoalexin and has been favorably implicated in cardiovascular disease and certain cancer processes. Foliar diseases were rated visually twice during the season. Berry disease ratings were made at harvest. All fungal foliage and berry diseases were significantly reduced by the fungicide treatments. Resveratrol concentrations were determined separately on berry skins, seed and pulp/juice by GC/MS. Overall, resveratrol levels in berry skins from unsprayed vines were much higher than those of sprayed vines. Concentrations varied by cultivar and within cultivar by treatment. The relationship of skin concentration and total disease score or scores of specific diseases has not been established. Seed resveratrol concentrations differed by cultivar but were not affected by the fungicide treatments. Mean concentration of seed was lower than that of skins. Accumulation of resveratrol in juice/pulp was much lower than in skins and seeds.

The effects of hydrogen cyanamide on budburst and fruit maturity of ‘Thompson Seedless’ grapevine

SummaryThe effect of hydrogen cyanamide (H2CN2) on budburst and fruit maturity of `Thompson Seedless' grapes was examined. Nine year old vines of cv. Thompson Seedless grafted on R.110 rootstock and supported on overhead tendone trellis (parral), were treated with either 2% or 4% of H2CN2, 53 and 67 d before expected budbreak and compared with unsprayed vines. The earliest treatment with 4% H2CN2 enhanced budbreak and advanced fruit maturity by 17 d. However, the same concentration applied 53 d before natural budbreak advanced the date of maturity by only 4 d. All the treatments increased significantly the percentage of budburst compared with the control. H2 CN2 had no significant effect on yield, but a positive effect on fruit quality. A higher index of maturity was obtained by the treatment: 4% H2CN2, 67 d before budbreak. All the treatments of H2CN2 induced more uniform budburst compared with the control. The best uniformity was obtained by the earliest spray using the higher concentration (4%).

Impact of Taedia scrupeus (Hemiptera: Miridae) Feeding on Cluster Development in Concord Grapes

Taedia scrupeus (Say) feeds on grape clusters and shoots early in the growing season. The impact of nymphal and adult feeding was assessed at the individual shoot level by confining nymphs within sleeve cages at 4 different times: prebloom, bloom, postbloom, and prebloom to postbloom. Prebloom feeding significantly reduced the number of berries per cluster and average berry weight, resulting in a 68% reduction in cluster weight. When nymphs were allowed to feed from prebloom to postbloom, cluster weight was reduced by 71%.Feeding only during bloom and postbloom did not affect cluster weight. Prebloom feeding reduced the number of florets per cluster, berries per cluster, and berry weight. The whole-vine impact of T. scrupeus was examined in a commercial Concord vineyard, where 3-vine experimental units were treated with carbaryl to remove T Scrupeus or were left untreated. Unsprayed vines, with a mean density of 20 T. scrupeus per vine, yielded 10.4 kg per vine, and sprayed vines without injury yielded 14.1 kg per vine. The yield component most strongly affected was the number of clusters per vine, which averaged 165.4 and 131.8 per vine in sprayed and unsprayed vines, respectively. Each T. scrupeus nymph was associated with 0.18kg of crop loss, suggesting that as few as 0.5 nymphs per vine can cause economic injury. Where treatment of vineyards to prevent T. scrupeus injury is warranted, it must be applied during the prebloom period.

Pest control on kiwifruit with an insecticidal soap

Field trials in 1988-89 and 1989-90 evaluated an insecticidal soap alone, with Bacillus thuringiensis (Bt) or an emulsified vegetable oil for pest control on kiwifruit. Insecticidal soap alone or with vegetable oil, reduced fruit damage by caterpillars (13 and 1%, compared with 41 and 14% on unsprayed vines). Addition of Bt post-flowering, gave control similar to that of a phosmet programme (both 2%). Insecticidal soap did not prevent armoured scale insects infesting leaves and fruit, or thrips damaging leaves. Dormant applications of chlorpyrifos with or without phosmet at before flowering improved early season scale control. Thrips control was enhanced by adding vegetable oil. A blemish resembling water staining affected 40% of the fruit on the vines treated with insecticidal soap alone or with vegetable oil.

Phytotoxicity investigations of mineral oil and diazinon sprays applied to kiwifruit in winter‐spring for armoured scale control

Abstract The effect of 1, 2, or 4% mineral oil (Mobil Superior 663 97%) sprays plus technical grade diazinon (24 g a.i./100 litres) applied to kiwifruit vines at various times from 35 days before to 25 days after budbreak, was investigated in orchards at Kerikeri, Te Kauwhata, and Motueka, New Zealand. There was no significant effect on budbreak, flowers, fruit, and yield parameters on treated vines compared with unsprayed vines at Te Kauwhata and Motueka. At Kerikeri the 4% mineral oil‐diazinon treatment caused phytotoxic damage to 25% of canes from an August application, 3% of canes from a September application, and no damage from an October application after budbreak. Damaged canes typically had 2–5 terminal buds which were dead. No damage was found at the 1 and 2% rates. At Kerikeri fruit numbers and yield of the mineral oil‐diazinon treated vines were significantly reduced compared to untreated vines. After adjusting for differences in cane numbers per vine, yield losses ranged from 13 to 17% for the...

A survey of armoured scale species (Hemiptera: Diaspididae) in kiwifruit orchards

Many armoured scale (Hemiptera: Diaspididae) are polyphagous and the various plants growing near orchards are potential hosts for scale which can invade adjacent kiwifruit, Actinidia deliciosa, vines. Scale insects were collected from sprayed and unsprayed vines, scale-free potted kiwifruit plants which were placed in orchards, infested kiwifruit from 3 packhouses and from alternative host plants adjacent to kiwifruit vines. A total of 2661 specimens from 7 districts were identified. Greedy scale, Hemiberlesia rapax (Comstock), was the most widespread species on kiwifruit, followed by oleander scale, Aspidiotus nerii Bouché and latania scale, Hemiberlesia lataniae (Signoret). The same species was usually dominant on both kiwifruit vines and adjacent alternative host plants.

Effects on fruit yield and on powdery mildew infection of fungicide and bactericide sprays applied to grapes during flowering

Abstract Benomyl 0.02%, dichlofluanid 0.1%, thiram 0.16%, and streptomycin 0.01% were sprayed twice during flowering on to the grape cultivars ‘Palomino’ and ‘Cabernet Sauvignon’. Yield and powdery mildew infection on the bunches were assessed 3 months later. None of the fungicides caused visible damage. The bactericide streptomycin reduced fruit set. Palomino but not Cabernet Sauvignon vines sprayed with benomyl produced significantly higher yields than unsprayed vines; yield from vines sprayed with dichlofluanid or thiram was not significantly affected. Vines sprayed with streptomycin produced significantly less fruit than unsprayed vines. Benomyl and dichlofluanid significantly reduced powdery mildew on both cultivars; thiram had no effect. Mildew was not assessed on the bunches of vines sprayed with streptomycin.

Berry Response of ‘Thompson Seedless’ and ‘Perlette’ Grapes to Application of Gibberellic Acid1

Abstract At a stage just after bloom, gibberellin (GA3) at 600 ppm induced maximum increase in berry size of ‘Thompson Seedless’ grapes. Seven days after fruit-set, only 25 ppm were required for maximum response. In both instances, regression lines of best fit between GA3 concentration and berry weight indicated a logarithmic response. At both late bloom and early fruit-set stages there was a large increase in berry size, but at a time halfway between these stages the response to GA3 was much less striking. After fruit-set there was a gradual decrease in response to GA3. Increase in berry size due to girdling, on both vines sprayed at bloom and fruit set with GA3 and on unsprayed vines was maximum when berry diameter was 3-10 mm at time of girdling. There was no interaction between berry response to girdling and to gibberellin application. At fruit-set, ‘Perlette’ berries generally responded to increases in GA3 concentration up to 600 ppm.

Effect on 'Thompson Seedless' Fruit of Gibberellic Acid Bloom Sprays and Double Girdling

The thinning of <i>Vitis vinifera</i> L. `Thompson Seedless9 fruit in response to gibberellic acid (GA) applied to vines during bloom was studied in Kern County, California. Also included was the response to GA treatment of fruit on double-girdled vines. With crop level per vine held constant, commercially mature clusters were significantly looser on vines sprayed with 5, 15, and 25 ppm GA at 10, 60, and 95% bloom than on unsprayed vines. The main reason was fewer berries per cm on The basal four laterals. Clusters were loosest from treatments at 60% bloom. Density of berries on hand-thinned clusters was significantly greater for thinning before than after shatter. Fruit from vines sprayed at 1.0 and 60% bloom shattered more during postharvest handling than fruit from unsprayed vines. Shot berries were fewer with prebloom thinning than with GA sprays applied during bloom, with the percentages of the latter related directly to the GA concentration and time of treatment being greatest for 10% bloom and least for 95%. The percentages were greater on the first and second laterals than on the third and fourth. Water berry formation was not conclusively affected by the concentration and timing of GA sprays. Thinning, whether done by hand before bloom or during bloom with GA sprays, increased the variability of water berry formation among the basal four laterals of the clusters. The degree Balling and Balling-acid ratio of fruit were significantly higher for hand-thinned before bloom and GA-thin ned during bloom than for vines thinned after shatter. They were also significantly higher for GA-thinned fruit than for hand-thinned fruit. Concentration of GA and time of application had no clear effect on either the degree Balling or Balling-acid ratio. Although berry size showed no clear relation to degree Balling in any treatment, it was directly related to Bailing-acid ratio in all but the unthinned treatment with very small berries (because the percentage of total acid decreased as berry size increased). The degree Balling was significantly higher for vines double-girdled at shatter or single-girdled at shatter plus another girdling when the fruit was 8-10°B than for vines single-girdled at shatter or single-girdled at shatter and the girdle reopened when the fruit was 8-10°B. Within, each pair of treatments the difference was not significant.