Canopy Management Research Articles

Harvest index of apple and kiwifruit – how high can we go by optimising plant architecture and canopy management?

Efficiency of plant function is measured using harvest index (HI), the fraction of annual fruit dry mass yield divided by the total annual dry mass of tree. HI describes the proportion of total annual biomass allocated into harvestable sinks. The HI of mature apple trees on dwarfing rootstocks is ~60-70%, higher than HI estimates of ~40% for kiwifruit vines. In a recent physiological study using tall spindle ‘Scilate’ (EnvyTM) apple planted intensively on M.9, a mature tree fruit yield of 105 kg tree(-1) fresh weight (175 t ha(-1) at 1667 trees ha(-1)) was achieved in the 9th year from planting. Average fruit dry matter content at harvest was 16.2%, suggesting a calculated annual dry weight fruit yield of 17 kg tree(-1) (28.3 t ha(-1)) in the 9th year. This mature tree yield was produced from minimal tree structure compared with traditionally-managed trees; the main axis and branches were slender in girth, and the mean dry weight of winter prunings following harvest in the 9th year was 0.62 kg tree(-1). Hence, high fruit yields were associated with little investment in standing tree structure and prunings, implying a very high tree physiological efficiency (HI). The HI of these ‘Scilate’ trees on M.9 in the 9th year was estimated to be 0.81. We speculate that HI of late season cultivars on M.9 could reach 0.85 with further optimisation of canopy management and tree architecture using artificial spur extinction. Exploiting vine architecture and optimising canopy management of kiwifruit may similarly improve yield and fruit quality by increasing vine HI. Preliminary results on whole vine behaviour (flowering, yield and vigour) in response to canopy architectural modification using spur pruning to reduce pruning intensity of ‘Zesy002’ (SunGold®) kiwifruit indicated that spur pruning did not modify yield but reduced vine dry weight of winter prunings by 50% after a single growing cycle. Ongoing work will compare vines managed by spur pruning and replacement cane pruning to quantify budbreak, flowering, yield and fruit quality responses over successive growing cycles.

The effects of cultivar and training system on vegetative growth of mango (Mangifera indica) orchards in Far North Queensland

Understanding how and why canopy structural growth imposes productivity limitations is critical to managing high yielding, regular bearing mango (Mangifera indica) orchards. This study aimed to see how vegetative and reproductive growth responds to canopy management including bending. To investigate the relationship between shoot architecture, flowering and fruiting we measured structural, functional and temporal patterns of branching and flowering at the tree, scaffold and growth unit levels. Mango architectural analysis found strong varietal effects on vegetative growth, while increasing tree density led to increasing flowering across the orchard area. Single leader medium density trees had a significantly higher mean flower count (m-3 canopy volume tree-1) compared to the conventional training systems, and there was no significant difference between the densities within the conventional system. Limb bending of a parent in the single leader training systems led to an increase in the length of children growth units (bent = 16.07 cm, unbent = 12.05 cm). This paper outlines briefly the techniques used to collect architecture data and summarises the first year of vegetative and reproductive growth in each of the management scenarios.

‘Gala’ apple performance with mechanical hedging in southern Brazil growing conditions

Different canopy management strategies have been used to reduce vigor and labor costs, including time of pruning and training system. “Fruiting wall” systems lend themselves to mechanical hedging, to control vigor and reduce labor costs. Hedging could eliminate the need for summer pruning. This trial evaluated different hedging times during the summer and different hedging intensities in a Brazilian orchard located at Vacaria-RS (-28,44 S; -50,85 W) on cultivar 'Maxi Gala' grafted on M.9 rootstock, planted in 2009, at ca 3,570 trees ha(-1), trained as tall spindle. Trees were hedged in 2014/15 at one intensity; in 2015/16 the same intensity used in 2014/15 was compared to a heavier one. The intense hedge uniformly narrowed the trees to 90 cm thick; the less intense narrowed the trees 120 cm thick at the base, 100 cm in the top. Hedging was applied at four different times during the southern summer: first weeks in December, January, February, March. Unpruned trees served as control. The lighter hedging in 2014/15 did not cause regrowth in any of the 4 treatment times. Yield was not affected in both years for the lighter pruning, while it was reduced in the intense hedge in 2015/16 if pruning were done in December. Fewer fruit dropped in the intense hedge in January than in December. Further observations need to be carried out, namely on growth, vigor and return bloom.

Bud load management on table grape yield and quality – cv. Sugrathirteen (Midnight Beauty®)

ABSTRACT Viticulture is an activity of great economic and social importance in the Submedium region of the Sao Francisco River Valley, with emphasis on table grape and wine production. With the increasing expansion of the viticulture, a growing number of alternatives that do not affect fruit quality have been studied to maximize table grape yield, such as pruning and load adjustment. The aim of the present study was to evaluate the influence of different bud loads on canopy management to enable the marketable and economic production of cv. Sugrathirteen (Midnight Beauty®) in the submedium region ofthe Sao Francisco River Valley. This study was carried out for two years (2014/2015) in an experimental area for the introduction of new cultivars patented by Prodomo Farm in the municipality of Petrolina, Pernambuco, Brazil. The experiment was conducted in a randomized block factorial 2 × 5 design, with two seasons and 5 treatments, 6, 8, 10, 12 and 14 buds short_textwhich correspond toshort_text 17, 23, 29, 34 and 40 buds·m–2 short_textrespectivelyshort_text, distributed in 4 plots, considering five plants per replicate. Our results show that pruning seasons significantly affected sprouting percentage. However, the difference in bud load influenced this variable, with higher values in the pruning at 14 buds in both seasons. According to the results, the selection of pruning system according to bud load and to genetic features of the cultivar, and their interaction with the environment, produced higher yields in pruning with 10 buds, without negatively affecting grape quality.

Palissage Reduces Cluster Zone Lateral Shoots Compared to Hedging

Summary Goals: Hedging grapevines is a common canopy management practice in vineyards in the northeastern United States, however it is criticized as being a short-term solution to vine vigor because it can stimulate lateral shoot growth, resulting in a repeated cycle of hedging and leaf removal that costs growers time and money. Palissage is an alternative canopy management tool where long shoot tips are tucked down into the canopy (i.e. Tuck) or wrapped horizontally along the top of the canopy (i.e. Wrap). Anecdotally, growers had reported that palissage initiated earlier cessation of shoot growth during the growing season and reduced or eliminated the need for leaf removal in the fruiting zone due to fewer lateral shoots. This work aimed to test the effects of palissage on vegetative and reproductive growth, yield, disease incidence and severity, and juice and wine sensory on Riesling ( Vitis vinifera L.) grown in northeastern United States. Key Findings Neither palissage treatment affected vine yield in 2015, but Tuck increased yield in 2016 compared to hedging. Wrap reduced the number of laterals in the fruit zone in 2015 but not 2016 compared to hedging. Tuck increased rachis length by 1.4 cm compared to hedging in 2016, but cluster compactness wasn’t reduced by either treatment. Tuck and Wrap decreased botrytis incidence slightly in 2016 when compared to hedging. A sensory panel found that wines grouped separately by treatment based on aroma. Impact and Significance: This study demonstrated that palissage – particularly Wrap - was a potentially viable canopy management technique to reduce lateral growth in the fruit zone. Impacts varied based on year, but in at least one year palissage reduced lateral shoot growth in the fruiting zone, increased rachis length, and maintained or increased yield, although fruit in the Tuck treatment was less ripe. The potential long-term impacts palissage has on vine vigor, yield, and fruit quality need to be further explored, but these methods hold promise to break the hedging-leaf removal cycle in vigorous vineyards.

Cordon Renewal Strategies for Declining Merlot Grapevines

Summary Goals: Some of the older vineyards in Washington have been exposed to recurring winter freeze events. Over the years this has resulted in gradual vine decline and reduced yields, prompting growers to consider vine renewal or replanting strategies. Unlike vineyard replanting, successful cordon renewal may result in a full crop within one to two years. The purpose of this study was to evaluate the potential of four different cordon renewal strategies to revive an aging and declining, cordon-trained and spur-pruned Merlot (Vitis vinifera) vineyard. Key Findings: None of the cordon renewal strategies tested succeeded in restoring adequate vigor in these vines. However, retaining three short canes (five to eight buds each) per cordon increased three-year average and cumulative yields compared with cordon removal, disbudding, and standard spur pruning. Higher yields were mainly due to higher numbers of clusters as a result of higher numbers of fruitful shoots. Cordon removal and retraining led to more uniform recovery than the other strategies, but no yield during the first year and intermediate yields during the next two years made this strategy economically less attractive than the short-cane approach. Complete disbudding of the cordon to encourage renewal of spur positions resulted in yields that were no better than those obtained with continued standard spur pruning. Disbudding also led to bushy growth initially, which may increase the cost of canopy management during the first year. In the first year, the low-yielding disbudding treatment resulted in somewhat higher fruit sugar accumulation. Otherwise, fruit composition was similar in all four pruning treatments, and the slight differences that were occasionally observed were within the expected range of technological maturity for high quality fruit. Impact and Significance: A three-year pruning trial conducted in a declining, cordon-trained Merlot vineyard indicated that retaining three short canes (five to eight buds each) resulted in higher crop production than other winter pruning methods. Although adaptive pruning strategies may have some potential to delay the need for replanting in vineyards that have incurred cumulative cold injury, such strategies may be effective only in conjunction with other cultural practices that enable vines to maintain or regain sufficient shoot vigor.

Urban Trees and Water Use in Arid Climates: Insights from an Integrated Bioeconomic-Health Model

Managing outdoor water use while maintaining urban tree cover is a key challenge for water managers in arid climates. Urban trees generate flows of ecosystem services in arid areas, but also require significant amounts of irrigation. In this paper, a bioeconomic-health model of trees and water use is developed to investigate management of an urban forest canopy when irrigation is costly, water has economic value, and trees provide ecosystem services. The optimal tree irrigation decision is illustrated for Albuquerque, New Mexico, an arid Southwest US city. Using a range of monetary values for water, we find that the tree irrigation decision is sensitive to the value selected. Urban deforestation is optimal when the value of water is sufficiently high, or alternatively starts low, but grows to cross a specific threshold. If, however, the value of water is sufficiently low or if the value of tree cover rises over time, then deforestation is not optimal. The threshold value of water where the switch is made between zero and partial deforestation is well within previously identified ranges on actual water values. This model can be applied generally to study the tradeoffs between urban trees and water use in arid environments.

Canopy management strategies to control yield and grape composition of Montepulciano grapevines

Background and Aims Higher temperature during the season is forcing growers in Central Italy to explore ways to reliably control vine yield and grape ripening, while maintaining grape composition. The most common approaches include altering winter pruning, shoot thinning (St), leaf removal and bunch thinning. These studies, however, rarely evaluated these practices in concert and over multiple seasons. Methods and Results From 2009 to 2013, five treatments were applied to Vitis vinifera L. cv. Montepulciano: winter pruning only (Wp, Control); Wp plus St; St plus pre-flowering defoliation (St + Dpa); St plus pre-veraison defoliation (St + Dpv); and St + Dpv plus bunch thinning (St + Dpv + Bt) applied prior to veraison. Effects on canopy architecture, yield, ripening and berry composition were measured. Compared to Wp, St, St + Dpv and St + Dpv + Bt treatments reduced leaf area and leaf layer number in the fruiting zone, while St + Dpv + Bt reduced yield. No treatment slowed ripening. The treatment St + Dpa reduced yield and the incidence of Botrytis cinerea, and improved fruit composition, but increased TSS in berries. All treatments were ceased after 2013 and the vines were pruned in winter only. The treatment St + Dpa imposed in 2013 had a strong carry-over effect on yield but not TSS in 2014. Conclusions Shoot thinning alone reduced canopy density but failed to reduce yield or improve fruit composition. Both the St + Dpv and St + Dpv + Ct treatments provided a more open fruit zone, had no effect on yield and increased TSS in fruit at harvest. Shoot thinning plus pre-flowering defoliation decreased yield and improved berry composition in a Mediterranean climate; however, given its observed carry-over effects on yield this approach should be applied only in alternate years, suggesting the need for further research exploring additional viticultural practices. Significance of the Study Despite some benefits of St, defoliation and bunch thinning on their own or even in concert, no combination tested was consistently effective for controlling vine yield and grape ripening, while maintaining grape composition.

Effects of 2,4-dichlorophenoxyacetic acid on the biochemical parameters and oxidative stress in rats: The protective role of pomegranate (punica granatum) juice

Arid pomegranate (Punica granatum) orchards are frequently rainfed. In these systems, orchard managers might be able to manipulate a stand’s canopy structure (e.g., thinning, pruning) to improve rainfall water input to the soil. The aim of this research was to determine how changes in management activities in rainfed pomegranate orchards in arid regions of Central Iran affects rainfall partitioning into throughfall, stemflow, and rainfall interception loss. We monitored gross rainfall, throughfall, stemflow and rainfall interception loss in three stands with varying levels of thinning and pruning. Management practices sufficiently altered the stand and canopy structure of pomegranate orchards to impact the quantity and pathway (throughfall v. stemflow) of rainfall reaching the ground. Decreases in tree height, canopy cover, crown length and LAI were correlated to a significant increase in rainfall reaching the forest floor. Results indicate that orchard managers may be able to prune 40% of the live crown and thin 70% of the stand if the objective it to significantly increase water inputs into the soil. Future research should focus on the impact of canopy management on soil moisture content and soil evaporation and transpiration.

Canopy management of macadamia trees and understory plant diversification to reduce macadamia felted coccid (Eriococcus ironsidei) populations

The macadamia felted coccid, Eriococcus ironsidei Williams, is an invasive pest in Hawaii that causes severe damage and yield losses in macadamia nuts. Developing integrated pest management options including effective conservation biological control is essential. Combining techniques of canopy thinning with the provision of nectar and pollen plant sources for beneficial insects in the understory may result in improved E. ironsidei suppression. The role of canopy modification and understory habitat in enhancing natural enemy effectiveness to reduce E. ironsidei populations was investigated. Plots with pruned trees plus wild plants had up to 48% less E. ironsidei than the control plots, and the pruned-only plots had up to 32% less E. ironsidei compared to the control plots. A greater abundance of natural enemies was found in the treated plots than in the control plots. Predatory beetles were up to 62% more abundant in the pruned trees plus wild plants than in the control plots, and in the pruned-only plots there were up to 54% more predatory beetles than in the control plots. Encarsia lounsburyi (Berlese and Paoli), a wasp that parasitizes E. ironsidei was up to 73% more abundant in the pruned plus wild-plant plots, and up to 50% more abundant in the pruned-only plots than in the control plots. Pruning macadamia trees potentially enhanced natural enemy populations within the orchards increasing predation from 36% to 60% and parasitism from 1.3% up to 4.3% compared to control plots. Yields of macadamia trees were not affected by the pruning during the period of the study, and current results suggest a potential increase in yields over time after pruning. This study provides evidence that pruned macadamia trees and understory plant species diversification support natural enemy populations and may provide enhancement of biological control of E. ironsidei in macadamia nut orchards.

Prolonged artificial shade affects morphological, anatomical, biochemical and ecophysiological behavior of young olive trees (cv. Arbosana)

Abstract Light requirement in olive trees is the most important factor to ensure both olive production and oil quality. However, in the intensive and hyper intensive olive cultivation, problems of shading frequently appear. The objective of this work was to study the effects of reduced irradiance on growth, morphology, anatomy, physiology and some biochemical traits of young olive plants. Thus, an artificial shade (ca. 60%) was performed in young olive plants cv. Arbosana. Plant responses occurred to shade application may be classified as short- and long-term ones. Shoot growth was started to be affected 18 months after shading application, and after that date a total suppression of growth was observed. However, both leaf surface and leaf angle insertion were affected from the beginning of the experiment (3 months).Shaded leaves had higher area and lower thickness. Palisade and spongy parenchyma thickness were reduced in shaded plants. Stomatal density, net photosynthetic rate, stomatal conductance and transpiration rate were also reduced by shade. Shading induced a significant decrease in the concentration of chlorophyll a, β-carotene, lutein and pigments within the xanthophyll cycle (VAZ). A significant decrease of fruits number was observed in shaded plants after one year of shading application, while with prolonged shade, a total absence of fruits were observed. In conclusion, the limitation of the amount of light intercepted by the olive canopy affects negatively most of studied parameters. Therefore, an adequate management of the olive canopy by applying adequate training and pruning programs or by the application of growth regulators will avoid shading problems with negative effects on vegetative growth and yield.

Physiological Strain in French Vineyard Workers Wearing Protective Equipment to Conduct Re-Entry Tasks in Humid Conditions.

The proper use of personal protective equipment (PPE) plays an important role in reducing exposure to pesticides in vineyard farming activities, including re-entry tasks. However, discomfort from clothing systems may increase the physiological burden on workers. We compared the physiological burdens of vineyard workers wearing three different types of PPE during canopy management in field humid conditions while accounting for occupational, climatic, and geographical environments. The study was conducted in the Bordeaux vineyards of southern France during June 2012. A total of 42 workers from seven vineyards consented to field observations. The following PPE garments were randomly allocated: HF Estufa polyamide (Brisa®), Tyvek® Classic Plus, and Tychem® C Standard. Participant sociodemographic characteristics were collected using a structured questionnaire. Skin temperature and heart rate were monitored continuously using portable devices. Multivariate multilevel linear regression models were performed to account for the hierarchical structure of data. No significant difference was found for mean skin temperature during work. Regardless of the cardiac strain parameter considered, the Tyvek® Classic Plus garment produced the poorest results (P ≤ 0.03). Under the very humid conditions encountered during the field study, the thinness and breathability of the Tyvek® Classic Plus garment resulted in undergarment humidity, imposing additional physiological burden on vineyard workers. These results confirm that the idea of using generic coveralls in any farming activity is unsuitable. Compromises should be created between physiological costs and protection, depending on the agricultural task performed, the crop grown, and the environmental conditions encountered.

Effect of shading in different periods from flowering to maturity on the fatty acid and phenolic composition of olive oil (cv. Arbequina)

Abstract In olive there is insufficient information about how radiation changes throughout different growing periods affect oil quality. The present three-season study was conducted on an 'Arbequina' orchard. In addition to control trees without shading (WS), four other treatments were applied to reduce solar radiation penetration to 50%: continuous shading throughout the experimental period (TS), shading from budbreak to fruit set (S1), from fruit set to pit hardening (S2), and from pit hardening to budbreak in the following season (S3). Shaded tree fruits from pit hardening to harvest had a lower maturity index and higher fruit production than the rest of the shading treatments. Free acidity and peroxide indexes were higher in S2 than in WS. Oleic acid was highest in oil from TS. Higher oleic acid content was found in S1 and S2 compared to S3 and WS. Linoleic and linolenic acids showed an inverse pattern to oleic acid. Phenol content was affected by reduced radiation in S2. Radiation reduction immediately after pit hardening was critical on fruit maturity, and indirectly, on the fatty acid and polyphenol content profile. Orchard design and subsequent canopy management should focus on improving canopy illumination during S1 and S2 where shading reduced both fruit production and oil quality. Shading in S3 markedly reduced oil quality but not fruit production.

High density orcharding and canopy management in guava

High density planting (hdp) is a highly efficient and advanced production system of fruit cultivation. High yield and good fruit quality can be achieved with a high density orchard in guava when the orchard has good light distribution throughout the tree canopy and there is a balance between vegetative growth and cropping. Guava bears on the current season emerging shoots. Regular pruning of shoots after fruit harvest encourages development of lateral shoots from which flowering occurs. Researchers from major guava growing countries like India, Mexico, Cuba, Venezuela, Australia, etc. have worked out the optimum plant density and canopy management techniques for higher yield and quality guava production. The techniques for ultra-high density (5000 plants ha-1) planting and rejuvenation of old, unproductive or senile orchards by canopy management have also been standardized in India. This paper reviewed the prospects of hdp and canopy management in guava.

Canopy Management of Table Grapes Cultivar in Tropical Conditions

Canopy Management of Table Grapes Cultivar in Tropical Conditions

Canopy management, leaf fall and litter quality of dominant tree species in the banana agroforestry system in Uganda

Small-scale farmers in the banana-coffee agro-zone of Central Uganda plant and maintain trees to provide a range of benefits. However, the impact of trees on soil fertility and crop yields is small. On many farms, trees exist in infinite numbers, compositions, with no proper spacing, sequencing and canopy management recommendations. The objectives of this study were to: quantify and compare leaf fall and leaf litter biomass for the dominant tree species subjected to different pruning regimes and during different seasons and determine the nutrient concentrations in leaf litter materials in order to assess their potential to improve soil fertility. A survey was conducted on 30 randomly selected farms to examine and document the tree species. Four tree species were dominant; Ficus natalensis (15.3%), Albizia coriaria (10.2%), Artocarpus heterophyllus (10.0%) and Mangifera indica (9.2%). Experiments such as canopy pruning, collecting leaf fall and weights of pruned leaf biomass were established for the four dominant trees on five randomly selected farms. A total of 120 trees were subjected to three pruning regimes (0%, 25% and 50%). Litter traps (1 m × 1 m) were placed 2 m from the tree trunk to collect falling leaves. Leaf biomass was collected from pruned branches and eighed. Leaf samples were collected from pruned leaves and a composite sample analysed for carbon and nutrient concentrations. Results showed that 40 tree and shrub species belonging to 21 families existed on farms. Leaf fall was highest in the dry season and A. Heterophyllus registered the highest amount. Leaf biomass from pruned trees was heaviest for M. indica (42.4 ±3 kg) in the wet season and at the 50% pruning regime (45.7± 2.1kg). Total nutrient concentrations were in the order A. coriaria > F. natalensis > A.heterophyllus > M.indica. We concluded that F. natalensis and A. Coriaria should be integrated more into the agroforestry system to improve soil fertility. A.heterophyllus and M.indica should be planted on farm boundaries. The 50% pruning regime was the best and should be carried out during the wet season. Key words : Tree species, canopy management, leaf fall, nutrient concentrations, soil fertility

Management of pomegranate (Punica granatum) orchards alters the supply and pathway of rain water reaching soils in an arid agricultural landscape

Arid pomegranate (Punica granatum) orchards are frequently rainfed. In these systems, orchard managers might be able to manipulate a stand’s canopy structure (e.g., thinning, pruning) to improve rainfall water input to the soil. The aim of this research was to determine how changes in management activities in rainfed pomegranate orchards in arid regions of Central Iran affects rainfall partitioning into throughfall, stemflow, and rainfall interception loss. We monitored gross rainfall, throughfall, stemflow and rainfall interception loss in three stands with varying levels of thinning and pruning. Management practices sufficiently altered the stand and canopy structure of pomegranate orchards to impact the quantity and pathway (throughfall v. stemflow) of rainfall reaching the ground. Decreases in tree height, canopy cover, crown length and LAI were correlated to a significant increase in rainfall reaching the forest floor. Results indicate that orchard managers may be able to prune 40% of the live crown and thin 70% of the stand if the objective it to significantly increase water inputs into the soil. Future research should focus on the impact of canopy management on soil moisture content and soil evaporation and transpiration.

Quality of olives: A focus on agricultural preharvest factors

Abstract More than 11 million ha of olives (Olea europaea L.) are currently grown worldwide, 98% of which are localized in the Mediterranean Basin, with olives being one of the most important fruit trees in the area. The olive fruit is a very particular drupe since it not may be directly consumed but must instead be processed. Table olives and virgin olive oil are the two main processed products derived from olive fruits. Both are considered staple foods of the Mediterranean Diet and have been produced in the area for centuries, presumably since olive domestication occurred approximately 6.000 years ago. Despite their long history and economic importance, the focus on quality is quite recent. The presence of various and copious amounts of bioactive compounds, some of which are exclusive to olives, is drawing attention to the nutraceutical value of these products. This review aims to integrate the available information regarding the quality of table olives and olive oil with a focus on how preharvest factors may affect quality. The first part of the review describes the main quality attributes considered for each product from different perspectives, including the legal, organoleptic and nutritional points of view, among others. The physiological mechanisms involved in fruit development and ripening, which significantly affect the quality of the fruits, i.e., the raw material for obtaining both products, are also discussed. The review also addresses the potential of both the considerable number of traditional olive cultivars and recent olive breeding programs to obtain products with distinct quality attributes (in terms of sensorial profile and bioactive compounds). Finally, the most recent literature concerning the effect of environmental (soil and climate) and agronomical factors (irrigation, fertilization, canopy management and harvesting) is extensively reviewed.

A Precision Pruning Strategy for Improving Efficiency of Vibratory Mechanical Harvesting of Apples

Abstract. The state of Washington is the biggest fresh market apple ( Borkh.) producer in the U.S., and the state’s annual apple production has exceeded 60% of the national production. Due to the extensive labor requirements for harvesting fresh market apples, there is burgeoning demand for mechanical harvest solutions. Our transdisciplinary studies on mechanical harvest systems for apples have shown that fruit removal efficiency (FRE) with a vibratory system can be improved with precision canopy management. In this study, we evaluated the effect of precision pruning strategies on FRE in two groups (106 and 107, respectively) of randomly selected horizontal branches of ‘Jazz/M.9’ apple trees in a commercial orchard. Fruiting lateral branches were pruned to either shorter than 15 cm (guideline 1, G1) or 23 cm (guideline 2, G2). Harvest tests were conducted using a shake-and-catch harvester prototype developed by Washington State University with a fixed vibrating frequency of 20 Hz and shaking duration of 5 s. FRE for branches treated with G1 was significantly higher (91%) than FRE for branches treated with G2 (81%). We recorded a negative relationship between FRE and lateral shoot length. FRE was up to 98% when shoots were shorter than 5 cm, and FRE was only 56% for shoots of 25 cm or longer. We developed a shoot diameter-to-length index (S-index) to better understand the effect of shoot size on FRE. FRE was as high as 98% when the S-index was greater than 0.15. In addition, mechanically harvested fruit quality was assessed by categorizing the fruit into Extra Fancy, Fancy, and Downgrade fresh market classes based on USDA standards; however, no significant difference was found between the two treated groups. These results suggest that pruning lateral fruiting branches to less than 15 cm or to an S-index greater than 0.03 is required to achieve FRE of 85% with no negative impacts on fruit quality. Keywords: Canopy management, Fresh market fruit, Fruit removal efficiency, Mechanical harvest, Shoot pruning severity.

Distinguishing One Year and Two Year Old Canes of Red Raspberry Plant using Spectral Reflectance

Red raspberry (Rubus idaeus) is one of the important horticultural crops around the world. Various canopy management activities such as cane pruning, bundling and tying are used in this crop to improve light distribution and air-flow through plant canopies, which will reduce pest stress and improve crop yield and quality. This operation, however, is highly labor intensive, which threatens the long-term, sustainability of the red raspberry industry as labor availability is dwindling and labor cost is increasing rapidly. Mechanized or automated pruning and bundling system could be a key to ease this problem and increase returns to the growers. First step in developing an automated pruning system is to distinguish one-year-old canes (called primocanes) and two-year-old canes (called floricanes), which could then be used by a robotic system to selectively remove floricanes from the mix of primocanes and floricanes. Floricanes and primocanes look similar in terms of color, shape and size of the canes during dormant season. Hence, a non-imaging spectroscopy method was investigated in this study to utilize spectral signature of primocanes and floricanes, which can vary between two types of canes based on their difference in moisture content and chlorophyll concentration. Forty samples of each floricanes and primocanes were collected in Nov 2017 from a plot of ‘Wakefield’ cultivar. Optimal wavebands were selected using Principal Component Analysis (PCA) and one-way ANOVA. Wavebands with the significance level of 5% were used. With a group of wavebands in the visible spectrum (596nm, 65nm, 676 nm and 716nm), primocanes and floricanes were distinguished with an accuracy of 91.7% using linear support vector machine. With a combination of wavebands from chlorophyll absorption and water absorption region (716nm, 856nm, 996nm, 1056nm, and 1396nm), a classification accuracy of 100% was achieved. Results show a promise for developing a multispectral sensor (with a few selected bands) for distinguishing between floricane and primocane. To our knowledge, this work represents the first study to compare the reflectance spectra signature to distinguish primocanes and floricanes of red raspberry plants.