Hail Nets Research Articles

The effect of two orchard light management practices on the sensory quality of apple: fruit thinning by shading or photo-selective nets

SummaryThe effects of innovative techniques for orchard light management on the sensory properties and quality of apple (Malus _ domestica Borkh.) fruit were measured using sensory and instrumental techniques. In the first experiment, ‘Rosy Glow’ fruit, thinned chemically or by shading, were compared. In the second experiment, ‘Fuji’ fruit were grown under five different coloured photo-selective hail nets and compared. For ‘Rosy Glow’ fruit, the efficacy of both thinning methods was comparable in terms of crop load, and no sensory differences were perceived between treatments by a trained sensory panel, based on quantitative descriptive profiling, except for the “green flesh” attribute. Nevertheless, ‘Rosy Glow’ fruit from the shade-based thinning had a higher mean fresh weight (FW; 215 g vs. 198 g) and higher titratable acidity (5.3 vs. 4.5 malic acid eq. 100 g-1 juice). Some significant differences were reported by the trained sensory panel for four out of the ten attributes rated among the ‘Fuji’ apples produced under the neutral black net (control), and the red, white, yellow, and blue photo-selective hail nets. Differences were greatest between fruit from the red and yellow hail nets. Apples from the red hail net had higher scores for yellow colour perception (average intensity 42.3 vs. 28.5, based on a linear scale anchored at 0 as the minimum and 100 as the maximum), sweet taste (score 54.9 vs. 42.4), and hardness (i.e., sensory definition for firmness; score 52.0 vs. 43.0), and a lower score for green colour (4.6 vs. 10.0). In terms of objective instrumental measurements, fruit from the red net treatment had a higher mean FW (217 g), with larger cells and larger intercellular spaces measured in terms of the number of cells mm-3 and the percentage of intercellular spaces, and a higher mean dry matter (DM) content [14.7% (w/w)], when compared to fruit from the other photo-selective net treatments. The spectrum of transmitted light influenced fruit growth by affecting cell proliferation and ripening, which changed the sensory perceptions of fruit appearance, taste, and texture.This study demonstrated that it is possible to use sensory panel analysis to measure the impact of new pre-harvest treatments on the quality of harvested apple fruit.

Photo-selective hail nets affect fruit size and quality in Hayward kiwifruit

The aim of the present research was to verify if photo-selective hail nettings can be used to affect fruit quality at harvest and during cold-storage, in addition to hail protection. The study was carried out in Southern Italy on 7-year-old Hayward kiwifruit vines. Four types of photo-selective hail nettings (blue, grey, red, and white) were compared with an un-netted control. The nettings affected differentially and significantly most of the qualitative parameters measured in this study. Both the white and the red nets appeared to be very interesting because they allowed a high dry matter accumulation in the fruit. This was translated into a high soluble solids concentration in the fruits during cold-storage. The blue and grey nets tended to affect negatively the percentage of dry matter and soluble solids content of fruit. This may be due to shading effects. In addition, the white and the blue nets had a slight negative effect on flesh chlorophyll concentration and colour. All the tested nets decreased polyphenol concentration and antioxidant activity of the kiwifruit at harvest. It is proposed that in case hail protection is a must, the right choice of photo-selective hail nets can lead to additional benefits, making the netting more cost-effective for the growers.

Effect of hail protection nets on apple scab in ‘Royal Gala’ and ‘Fuji’ apple cultivars

In commercial apple orchards in Southern Brazil, it is common to avoid hail damage by covering the trees with nets. However, this technology can affect the epidemiology of some apple diseases, specially the apple scab (AS). This study was carried out to assess the effects of both black and white hail netting on the temporal dynamics of AS disease in a commercial ‘Royal Gala’ and ‘Fuji’ apple orchard in a high-altitude region of Southern Brazil during two growing seasons. Apple trees on M9 rootstock, trained to a slender spindles and with a spacing of 3.5 m × 0.8 m, were left uncovered (control condition) or covered with black or white hail netting. The incidence and severity of AS were quantified biweekly from October to February by evaluating 100 leaves distributed randomly on four medium-height branches per plant with 12 replications. Disease progress curves were constructed and the epidemics were compared by four epidemiological measures: the beginning of symptom appearance (BSA), the time to reach the maximum disease intensity (TRMDI), the maximum value of disease severity (Ymax), and the area under the disease progress curve (AUDPC). The highest intensity of AS was observed in the plants under the black hail netting. Reductions in BSA and TRMDI and increases in Ymax and AUDPC by the hail net were found in both ‘Royal Gala’ and ‘Fuji’ cultivars and growing seasons. Differences between white hail netting and control condition on BSA and TRMDI for AS were found in both cultivars and growing seasons. However, no differences between white hail netting and control condition on AUDPC for AS were found in both cultivars and growing seasons, except for ‘Fuji’ cultivar in 2004/05 growing season. The results of the study showed that the hail protection system using black hail netting is susceptible to increase the intensity of apple scab more than white hail netting.

Effect of hail nets on the microclimate, irrigation requirements, tree growth, and fruit yield of peach orchards in Catalonia (Spain)

SummaryHail nets protect orchards from storm damage, but also offer potential water savings for fruit trees grown in arid areas. We investigated the effects of black nets on water use, growth, yield, and fruit quality in peach trees growing in Catalonia, Spain, over 2 years (2006 and 2007). Water savings were quantified by irrigating the netted trees to a similar midday stem water potential (Ψstem) as the control trees. This method was only partially successful in 2006, with the netted trees being over-watered early in the season (i.e., higher Ψstem than the controls), and under-watered (i.e., lower Ψstem than the controls) later in the season. A combination of water stress and a hail net resulted in lower yields because of a smaller fruit size. Skin colour was more enhanced in control fruit. In 2007, Ψstem values were similar between treatments. Any difference in tree performance was therefore due to the hail net per se. Fruit size was similar between treatments, and the lower yields of netted trees were due to decreased fruit number. There were no treatment differences in fruit skin colour or flesh firmness. Soluble solids concentrations were higher in nonnetted fruit. In both years, water savings amounted to approx. 25%, if irrigation replaced the potential evapotranspiration that was measured. Hail nets are therefore recommended for their effects on water saving in arid areas, despite lower fruit yields.

Effects of excessive weather on the micro-climate of apple plantations under the hail protection nets

The general utilisation of hail nets is spreading all over the world and in Hungary too. Hail nets are at present the only tool, whichis able to prevent heavy hail damage in agricultural crops. Besides its numerous advantages, there are also deleterious side effects, e.g. itchanges the microclimate of the crop stand. Our study aimed to observe the differences, which characterise the physical status of crop standsunder the protection of hail nets compared with the stands in open air under various meteorological conditions: high or low temperature, calmor windy atmosphere and their possible combinations. The results indicated that on hot and calm days the difference may attain 3–4° C. Oncool summer days, the difference was only 1.5 ºC. The hail net influences the relative humidity of the air, which means on ho summer daysoften 7-8% differences. Conditions of radiation may also differ conspicuously. Measurements prove the reduced global radiation on sunnysummer days to 70%. This impairs as a rule the development of fruits reducing their quality and also its quantitative traits. Sunburn is, on theother hand, significantly prevented by shadow.

Economic aspects of applying hail protection nets in apple plantations

The up to date intense apple growing in Hungary is capable to produce yearly about 500-1000 thousand Ft/ha income, which means that the investment of 4 000–5 000 thousand Ft is returned by producing 10-20% net income. The economic balance may, however, be upset by the damage caused by hail, quantitative and qualitative, with an apparently increasing frequency experienced in each third or fourth year. Estimates prove that each hail causing 50% damage may reduces the income proportionately to the capital by 1.5–2.0 percent points, which means a serious threat for the economy of apple production. According to calculations, a plantation producing 30–40 t/ha yields would not be able to raise incomes compensating the investment of 7.0–10.0 million Ft/ha, let alone the frequencies of hail damages. Consequently, 50–60 t/ha yields are needed to become successful, and in planning of new plantations those high yields are aimed with hail nets. An additional difficulty is represented by a lack of financial resources to install hail protection nets.

Reflective materials under hailnet improve orchard light utilisation, fruit quality and particularly fruit colouration

The increase in hailstorms, possibly due to climate change, has led to installation of hailnets in fruit orchards worldwide. This is associated with poorer fruit quality, particularly fruit colouration, which is determined by the light conditions viz diminishing light intensities and shorter day length in the autumn. To overcome these adverse effects of hailnets, five materials were examined as possible ground covers as to their light reflection and the subsequent effect on fruit quality including fruit colouration, using a 9-year-old apple orchard cv. ‘Gala Mondial’ on M9 under black hailnet near Bonn. The ground covers included the woven white plastic Extenday R/Daybright™, the kaolin-coated, bio-degradable paper UniSet O™ and the aluminium-coated plastic Mylar™ and Svensson ILS Alu™; the latter is a white plastic interwoven with aluminium strips used as energy saving screen in greenhouses. The ground covers were spread in the alleyways 4–5 weeks before anticipated harvest; adjacent uncovered grass strips under the hailnet served as control. Light reflection, measured perpendicular at 1 m height in the alleyways at the time of fruit colouration, was 79–80% by Extenday R/Daybright™, 75% by UniSet O™, 68% by Mylar™ and 58% by Svensson Alu ILS™. Apple fruit with any of the reflective ground covers ripened 2–3 days earlier without affecting internal fruit quality and sugar as indicative of taste. The reflective ground covers under black hailnet improved the proportion of well-coloured class I fruit relative to the control (uncovered grass) by an averaged 9%. Economic analysis showed that Extenday R, with an expected lifetime of ten years (based on 4–6 weeks spread time per year) under hail nets in North-Western Europe, scored best based on 45 t ha −1 yield in cv. ‘Gala Mondial’ and 0.40 € kg −1 farm-gate price, resulting in 200 € ha −1 net return. Manual labour for spreading and retrieving the ground covers had the major share of the overall gross cost and offers scope for improvement by mechanisation.

Influence of Hail Net and Reflective Foil on Cyanidin Glycosides and Quercetin Glycosides in ‘Fuji’ Apple Skin

The objective of this work was to compare the contents of cyanidin glycosides and quercetin glycosides in the skin of apples grown with or without hail nets and using reflective foil or not. Under hail nets, photosynthetically active radiation was 10% to 30% lower in comparison with the control treatment. Covering the orchard floor with reflective foil had a positive effect on lighting, particularly on the lower parts of the fruit. Fruit coloration depends on the contents of anthocyanins copigmented with flavonols, the synthesis of which is light-dependent. The content of the main cyanidin glycoside in ‘Fuji’ apple, cyanidin galactoside, was lowest in the control treatment as well as concentrations of cyanidin arabinoside and two other cyanidin pentosides. Reflective foil caused a higher cyanidin glycoside content. Among flavonols, quercetin galactoside, quercetin glucoside, quercetin pentoside, quercetin arabinofuranoside, quercetin xyloside, quercetin rutinoside, quercetin rhamnoside, and quercetin were detected. Hail net and reflective foil both affected the increasing quercetin–glycosides contents. The highest amounts were achieved in the treatment under the hail net, where the orchard floor was covered with reflective foil. We also analyzed catechin, epicatechin, and chlorogenic acid. The lowest amounts of these were measured in the skin of fruit grown on trees under hail nets. In the control treatment, contents of those phenolic compounds were equal or higher, whereas the highest concentrations were detected in the treatments using reflective foil, where lighting was also higher in comparison with the treatments without it.

Haplotype diversity of Tilletiopsis spp. causing white haze in apple orchards in Northern Italy

White haze (WH), a manifestation of extensive colonization of anamorphic smut fungi of the genus Tilletiopsis on the surface of apple fruit, has recently been described as a new postharvest disorder of the cultivar Elstar. This study shows that these fungi can also affect apple fruit of different cultivars prior to harvest, and therefore seriously compromise the quality of the produce in Northern Italy. In order to identify the Tilletiopsis taxa involved in the induction of WH in this region, 48 isolates, mainly derived from fruit samples, were analysed by DNA sequencing of the internal transcribed spacer region. Six haplotypes were identified that could be assigned to three different phylogenetic lineages, the T. washingtonensis group, the T. pallescens group and the Entylomataceae. More than 40% of the isolates were classified as T. washingtonensis which had not previously been associated with WH. Furthermore, this is the first study that reports the occurrence of this species on field‐grown fruit samples. The extensive overgrowth of apple fruit by Tilletiopsis spp., appearing erratically in the last decade, may be a consequence of moist weather conditions and novel cultural practices, such as the use of hail nets and the intensive application of foliar nutrients.

Does the microclimate under hail nets influence micromorphological characteristics of apple leaves and cuticles?

A higher frequency of hail storms, possibly due to climate change, has led to increased installation of hail nets worldwide. The objective of the present work was to investigate potential effects of the microclimate under these hail nets on micromorphological characteristics of the leaves and adaxial leaf cuticles. Leaves of apple cultivars 'Pinova' and 'Fuji' grown on trees under white (highly translucent) or red-black (low transmittance) hail nets or on uncovered (control) trees were evaluated in June, August, September and October. The microclimate under the colored hail nets had no impact on leaf micromorphology, amount of cuticular wax, or leaf thickness. Similarly, no differences in thickness and permeability for calcium could be established between cuticles of leaves grown on trees under the two types of hail nets or uncovered trees. For all evaluated parameters, significant differences were detected between the two cultivars examined. In both cultivars, leaf wax synthesis followed a characteristic curve, increasing from the first to the second evaluation, and then decreasing continuously without affecting cuticular penetration of calcium. Overall, our results show that a reduction of the hail nets by 6-10% in both light and humidity was insufficient to influence the surface properties of apple leaves and permeability of cuticles. This may suggest that pest management strategies, i.e. formulation of agrochemicals, their application and dose, do not need to be adapted when used under hail nets. Overall, the present results indicate that the microclimatic changes brought about by colored hail nets are sufficient to enhance the vegetative growth and induce the 'shade avoidance syndrome', but do not appear to affect the leaf cuticular properties.

The effect of reflective foil and hail nets on the lighting, color and anthocyanins of ‘Fuji’ apple

We studied the influence of covering the orchard floor with reflective foil on photosynthetic active radiation (PAR) both under and outside hail nets, and the possibility that the reflective foil under the hail net compensates for light reduction in last month before harvest time. On the lower side of fruit in the canopy, the reflective foil increased PAR. The chromaticity value a * showed a difference in the intensity of red coloration in the reflective foil and hail net treatments. Amounts of individual cyanidins were detected by using HPLC–MS. The accumulation of five individual anthocyanins (cyanidin-galactoside, three cyanidin-pentoses and cyanidin) was investigated during last month before harvest time. Concentrations of the main, cyanidin-galactoside in ‘Fuji’ apple increased before harvest time, and at harvest time the reflective foil caused an increase in all identified anthocyanins.

Modelling the phenology of codling moth: Influence of habitat and thermoregulation

This study used an explorative, individual-based model to evaluate the influences of (1) plant architecture, i.e. dwarf versus standard trees, (2) the use of hail nets, and (3) insect behaviour on the phenology of the codling moth, Cydia pomonella (Lepidoptera: Tortricidae), a major pest in apple orchards worldwide. Body temperatures of the different codling moth stages were approximated by microhabitat temperatures, behaviouralresponsetotemperature,andbiophysicallymodelledtemperatureincrementsduetoabsorptionofsolarradiation.Results indicate a significant influence of habitat parameters on the phenology of the codling moth. Under the simulated conditions, adults appeared up to 6 days earlier in dwarf trees than in standard trees, and up to 5 days later in trees covered with hail nets than in trees without them. In contrast, thermoregulation behaviour, which is documented for the larval and adult stages, appeared to be of relatively low influence on the insect’s overall phenology. Model validation using reported pheromone trap catches of male moths agreed with the simulated appearance dates of adults of the overwintered generation. Simulated and observed appearance dates did not deviate when habitat temperature was used, but deviated considerably when standard air temperature was used as driving variable. Considering habitat and behaviour will help to improve current phenology models for the codling moth. # 2006 Elsevier B.V. All rights reserved.

Effect of plant architecture and hail nets on temperature of codling moth habitats in apple orchards

AbstractPlant architecture of apple trees in commercial orchards was rapidly changed from traditional tall trees to dwarf trees to optimize yield and fruit quality. Additionally, hail nets are widely used to prevent yield loss by hail. These changes are expected to considerably influence the orchard microclimate and thus the developmental rates of pest insects in apple. However, these relationships have not yet been fully elucidated. The present study was conducted over the seasonal cycle to investigate the influence of plant architecture and hail nets on the habitat temperatures of the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), in apple, Malus domestica Borkh. (Rosaceae). Within the canopies, leaf area index (LAI) and global site factor (GSF) were quantified using hemispherical photography. Temperature was analysed for the main habitats of the different codling moth stages, i.e., air within the canopy, bark of tree stems, and apple fruit. In dwarf trees, LAI was lower, leading to a higher GSF than in tall trees. Hail nets did not influence LAI and GSF. Results for dwarf trees compare as follows with those for tall trees: Average air temperatures within the canopy were 0.7 °C higher during daytime, whereas 0.4 °C lower at night. Mean surface temperatures of bark were 0.9 °C higher on sunny and 0.4 °C on overcast days. Mean surface temperatures of apple fruits were 1.8–2.7 °C higher on sunny days, but 0.6 °C cooler on overcast days. The effect of hail nets was confined to a reduction of the air temperature within the canopy by approximately 0.2–0.8 °C. Bark and apple surface temperatures were not significantly affected. Based on the temperature differences in the habitats considered, the calculated development of the codling moth in dwarf trees was on average 3 days faster than in tall trees. The calculations imply a negligible effect of hail nets on codling moth development.

Radiotracking of Myotis myotis (Chiroptera, Vespertilionidae) in South Tyrol and implications for its conservation

In Central Europe, greater mouse eared bats (Myotis myotis, Chiroptera: Vespertilionidae) are simultaneously reliant on man (for maternity roosts) and adversely affected by him (e.g. landscape destruction). This is a common situation for most of the Central-European bat species. In South Tyrol, however, large maternity colonies of mouse eared bats are often situated amidst zones of intensive apple growing and they usually thrive. A radiotracking study conducted in July 2000 and 2001 shows strong foraging activity in the valley bottom and nearby slopes. The elongation of the home range was 15 km, core areas ranged from 2 to 6 km away from the nursery. The greater mouse eared bats mainly used intensively cultivated orchards and deciduous shrub forests. Mature forests, meadows and pastures were scarcely used. Unfortunately intensification in apple growing; eliminating high trees and covering orchards with hail nets, is an ongoing process. To preserve greater mouse eared bats it is necessary for them to continue using the orchards in the future. So it seems necessary to convince farmers that bats in the orchards are beneficial.