Single-tree Replicates Research Articles

Evaluation of biopesticides for the control of Erwinia amylovora in apple and pear

With increasing organic acreage and scrutiny of antibiotics use, alternatives to antibiotics for the control of Erwinia amylovora are of interest to stakeholders. At the same time failures of minimally tested, newly marketed products have resulted in severe infections leading to costly tree and orchard removal. We evaluated antibiotic alternatives in 8 Washington, 3 Oregon, 3 New York and 2 Pennsylvania field experiments conducted 2013 to 2022. Antibiotic alternatives included essential oils (thyme and cinnamon extracts), mineral compounds (potassium aluminum sulfate), oxidizers (peracetic acid-peroxide), soluble coppers (copper octanoate, copper hydroxide, copper sulfate pentahydrate), and biological controls (Aureobasidium pullulans, Bacillus subtilis, bacteriophage). Studies were conducted in ‘Bartlett’ and ‘dAnjou’ pear, ‘Gala’, ‘Cameo,‘ and ‘Red Delicious’ apple with 4 to 6 single-tree replicates arranged in a randomized complete block inoculated with E. amylovora at 80–100% bloom. In summary analysis of 8 Washington trials Alum (potassium aluminum sulfate), Blossom Protect (A. pullulans) and several copper products (Previsto, Mastercop, Instill) provided good disease suppression of 70–73% similar to antibiotic checks. Several essential oil, copper, and peracetic acid-peroxide and biological products (Serenade Opti, Cueva, Oxidate 5.0, Jet Ag, Thyme Guard and Thymox) provided intermediate disease suppression between 45 and 62% significantly better than the water-treated control. In multistate trials Alum with 2–3 applications provided good control in most experiments (means 2019: WA 79%, NY 77%, PA 57%; 2020: OR 86%, NY 65%, WA 28%; 2021: NY 87%, WA 50%). Essential oils with 3–4 applications provided intermediate control NY 2021 81% control 23% thyme oil, 70–85% control NY 2020, 2021 60% cinnamon oil.

Effects of Iron Rates on Growth and Development of Young Huanglongbing-affected Citrus Trees in Florida

Essential nutrients for citrus [‘Bingo’ (Citrus reticulata, Blanco)] production are important for different functions, including photosynthesis, resistance to disease, and productivity. During the past 15 to 20 years, citrus production in Florida has significantly declined as a result of the devastating citrus greening disease also called huanglongbing (HLB). Therefore, a greenhouse study was conducted for 2 years, starting in 2018, at the University of Florida/Institute of Food and Agricultural Sciences Citrus Research and Education Center in Florida to evaluate the effect of varying rates of iron on the growth and development of 2-year-old HLB-affected ‘Bingo’ (Citrus reticulata, Blanco) trees on Kuharske citrange rootstock. Four treatments were used in a randomized complete block (HLB status) design with seven single tree replicates for each treatment. The treatments applied were 0.0 (control), 5.6 (standard fertilization, lx), 11.2 (2x), and 22.4 (4x) kg⋅ha−1 iron on HLB-affected and healthy (non-HLB) citrus trees. Data including trunk diameter, tree height, and leaf samples were collected, processed, and analyzed at 3-month intervals for 2 years. At the end of the second year, trees were destructively sampled and processed as above-ground and below-ground biomass. Tree heights were different among iron rates of HLB-affected trees (P < 0.001); however, they were similar for non-HLB trees for both years. Higher average trunk diameters (P < 0.001) were observed for HLB-affected trees that received the 2x rate compared with the 1x rate and the control. In 2019, non-HLB trees showed 13% to 40% higher iron concentrations in leaves than HLB-affected trees. However, leaf iron concentrations were comparable for HLB-affected and non-HLB trees in 2020. Above-ground biomass for HLB-affected trees had between 33% and 44% more biomass (P < 0.01) than below-ground biomass for the corresponding iron fertilization. Iron accumulation correlated positively with all studied nutrients in the above-ground parts for both HLB-affected and non-HLB trees. A 95% confidence interval at which total biomass was nearly maximum corresponded to an iron rate of 9.6 to 11.8 kg⋅ha−1, which was close to the 2x rate. Therefore, soil iron application using the aforementioned rates may be appropriate for better growth and development of young HLB-affected trees.

Variable Manganese Rates Influence the Performance of Huanglongbing-affected Citrus Trees in Florida

Improving nutrient uptake and tree health play an important role in managing Huanglongbing (HLB)-affected citrus trees in Florida. A greenhouse experiment was conducted to evaluate the effect of increasing rates of manganese (Mn) on growth and development of sweet orange [Citrus sinensis (L.) Osbeck] trees at the University of Florida’s Institute of Food and Agricultural Sciences (UF/IFAS) Citrus Research and Education Center in Lake Alfred, FL. Half the trees were graft-inoculated with the HLB pathogen and the remainder were used as the HLB-free (non HLB) control trees. Four rates of Mn (0.0 kg·ha−1 Mn (Control), 5.6 kg·ha−1 Mn (1x—standard rate), 11.2 kg·ha−1 Mn (2x—standard rate), and 22.4 kg·ha−1 Mn (4x—standard rate) were split applied quarterly to both sets of the trees in a completely randomized design. There were seven single tree replicates for each treatment. Response variables measured were trunk diameter, tree height, leaf Mn concentration, plus above- and belowground biomass. The accumulated Mn in leaf tissues significantly increased trunk diameter but did not affect tree height for both HLB-affected and non-HLB trees, the 2x rate had the maximum value for trunk diameter relative to the 4x rate. This study established a positive correlation between soil available Mn with Fe and Cu, but negative correlation with B and Zn. A strong correlation of −0.76, −0.69, and 0.65 was observed between soil Mn and B, Zn, and Cu, respectively, as compared with 0.49 with Mn and Fe. Among HLB-affected trees, the 2x rate gave the most belowground dry matter, which was 3% greater than the control and 5% greater than 4x. Aboveground dry matter had at least 30% more biomass than belowground matter among all treatments within HLB-affected trees. For small and medium roots, Mn accumulation increased with Mn application until 2x rate and decreased thereafter for HLB-affected trees. The results from our study showed an Mn rate of 8.9–11.5 kg·ha−1 Mn, as the optimum Mn level for young ‘Valencia’ HLB-affected trees in Florida.

EARLY SPRING APPLICATION OF AMINOETHOXYVINILGLYCINE (AVG) INCREASES FRUIT SET AND YIELD OF ‘ROCHA’ PEARS

ABSTRACT The low fruit set is one of the main factors leading to poor yield of pear orchards in Brazil. Ethylene is associated with abscission of flowers and fruitlets. Then, the application of ethylene synthesis inhibitors, such as AVG, is a potential tool to increase fruit set of pears. The objective of this study was to evaluate the effect of AVG, sprayed at different rates and timings, on fruit set, yield and fruit quality of ‘Rocha’ pear. The study was performed in a commercial orchard located in the municipality of São Joaquim, SC, during the growing seasons of 2014/2015 and 2015/2016. Plant material consisted of ‘Rocha’ pear trees grafted on quince rootstock ‘BA29’. AVG was tested at different rates (60 mg L-1 and 80 mg L-1) and timings [full bloom, one week after full bloom (WAFB), and two WAFB), either alone or in combination. The experiment was arranged in a randomized block design, with at least five single-tree replications. The fruit set, number of fruit per tree, yield, estimated yield, fruit weight, return bloom, and fruit quality attributes were assessed. Fruit set and yield were consistently increased by single applications of AVG at 60 and 80 mg L-1 at both one and two weeks after full bloom, without negatively affecting fruit quality attributes and return bloom.

Prohexadione calcium controls shoot growth of pear trees

The aim of this study was to evaluate the effects of prohexadione calcium (PCa) on vegetative growth and production of ‘Carrick’, ‘Packham’s’ and ‘William’s’ pear. The trial was performed at the experimental field of the Federal University of Pelotas, Capão do Leão, RS, Brazil (31º 52’ 00" S; 52º 21’ 24" W), during the growing seasons of 2011 and 2012. Treatments were applied to single-tree replications in a randomized complete block design with four replications as follows: Control (unsprayed), PCa (PCa - 750 g ha-1 i.a.). The application was split in four (187,5g ha-1 a.i. each) and three timings (250g ha-1 a.i. each) in the 2011 and 2012 growing seasons, respectively. The assessed parameters were: shoot length, trunk cross sectional area (TCSA) increment, number of nodes, internode length, pruning weight, number of fruits, average fruit weight, production per tree and return bloom. It was possible to conclude that application of PCa at 750 g. ha-1 a.i satisfactorily controls shoot growth through the reduction of internode length of ‘Carrick’, ‘Packham’s’ and ‘William’s’ pears. Besides, it was observed that return bloom is not negatively affected by PCa. So, this plant growth regulator is a potential management tool to reduce shoot growth and the need for pruning in pear orchards.

Peach cell number and size is affected by crop load and cultivar

Peach fruit development is impacted by crop load, cultivar genetics, and temperature during the Phase I growth stage after fruit set. Four peach cultivars, 'Carored', 'Summerprince', 'Scarletprince' and 'Redhaven', ripening from mid-May to early July were selected for fruitlet sampling every 5 days from week 2 to week 5 post-bloom. Fruitlets were collected mid-shoot, 1.5 m above ground, from the exterior of all four sides of the tree. Fruitlets were fixed with FAA (ethanol-formaldehyde-acetic acid) before mounting for sectioning. Trees of each cultivar were either thinned one week or four weeks after petal fall. There were four single-tree replicates for each cultivar and treatment. Mesocarp cell number and size were recorded from transverse sections using Infinity Analyze software. Differences in cell number due to crop load were observed within days after early thinning. Early thinned trees had 8 to 19% more cells than later thinned trees 3 weeks after the first thinning date. At week 4 post-bloom, the two later ripening cultivars, 'Redhaven' and 'Scarletprince', had more cells than the two early ripening cultivars. Differences in cell size occurred with 5 days of thinning for the earliest cultivar, 'Carored'. The other 3 cultivars did not see differences in cell size between treatments until 2 weeks after the earliest thinning treatment. Three weeks after the early thinning, fruit from early thinned trees had cells 5% ('Summerprince') to 43% ('Carored') larger than the later thinned trees. At week 5, early cultivars had larger cell size than the later ripening cultivars. Fruit from the early thinned trees ripened earlier and were larger at harvest.

Manipulating time of bud break, flowering and crop development of sweet cherry with the dormancy breaker Waiken®

Trials were conducted over two seasons to determine the effect of late winter applications of the rest breaker Waiken® (an emulsified vegetable oil compound, SST Australia Pty Ltd) on flowering and spring growth of sweet cherry cultivars 'Vista' and 'Sylvia'. Trial design in all trials was a randomised complete block with 10 single tree replicates. An untreated control was included in all trials and Waiken was applied to dormant trees. In the first season, Waiken was applied at 4% by volume to drip point to 'Vista' trees on 4th August (approx. 7 weeks before budburst). Treatment advanced and concentrated the flowering and harvest maturity and also reduced apical dominance and increased leaf canopy development in spring. The following season trials were established on 'Vista' and 'Sylvia'. In the 'Vista' trial, 4% Waiken was applied as a single application at four different times NDASH the earliest on 2 August (54 days before budburst (dBBB)) and the latest application on 27 August (30 dBBB). In the 'OSylvia' trial, 4% Waiken was applied at either 73 dBBB (2 August) or 60 dBBB (15 August). In both cultivars, earlier applications of Waiken advanced bud break, flowering and fruit maturity by approximately 7 days. Later application of Waiken at 30 d BBB delayed bud development and flower opening, reduced the length of the flowering period and concentrated fruit maturity. Waiken increased early canopy development at all timings but to a greater degree with earlier applications (up to 300%). This work has demonstrated that Waiken is effective in manipulating budbreak and flowering in sweet cherry and has potential to delay bud and flower development to help avoid frost in frosty areas. However further work is needed to determine how late it can be applied to delay bud break in cherries.

First Report of Diplodia seriata Causing Pear Branch Canker Dieback in California

California produces 26% of the United States pear crop on approximately 5,600 ha. A survey of seven northern California pear orchards (Pyrus communis cv. Bartlett) in summer 2010 revealed the presence of wedge-shaped cankers on 2- to 5-cm diameter branches, equating to 1- to 3-year-old wood. Many of the observed cankers occurred near pruning wounds, and there was decreased foliation on infected branches. Infected wood was surface disinfected with 95% ethanol and briefly flamed. After removing bark, small sections of diseased tissue were plated onto 4% potato dextrose agar (PDA) amended with 0.01% tetracycline and placed on the lab bench at 22°C until fungal growth emerged. Fungal colonies that were consistently isolated were transferred to fresh PDA using hyphal tip isolation. Fungal colonies were dark brown to gray with aerial mycelium and formed pycnidia after 15 days of incubation at 22°C. Conidia were brown, oval to oblong, and measured (16.5-) 20 to 24 (-26) × (7.5) 8.75 to 11 (-12.5) μm (n = 50). DNA from 14- to 21-day-old colonies was extracted and sequences of the rDNA internal transcribed spacer region and part of the β-tubulin gene were amplified using primers ITS4/ITS5 and Bt2a/Bt2b, respectively (2). The DNA sequences of fungal isolates from California showed 99 to 100% homology with the ex-type Diplodia seriata De Not. (1) CBS112555 deposited in GenBank. DNA sequences from three California isolates were submitted to GenBank with accession numbers KC937062, KC937065, KF481957, KF481598, KF481959, and KF481960. Pathogenicity tests were performed in March 2011 on 3-year-old Bartlett pear trees planted at an experimental farm in Davis, CA. A single, circular, 2-cm pruning wound at the top of the trunk was inoculated on each of three single-tree replications using 2-cm mycelial plugs from 14-day-old colonies growing on PDA. After inoculation, mycelial plugs were covered and sealed with Parafilm and aluminum foil for the duration of the trial. Three control trees were inoculated using sterile PDA plugs. Twelve months after inoculation, UCD103 and UCD105 were consistently re-isolated from the margin between necrotic and healthy tissue using the same methods described for the original isolation, and UCD102 was re-isolated in two out of three plants. The average lesion lengths of UCD102, UCD103, UCD105, and control plants were 12.5, 17.3, 23, and 1 mm, respectively. Control lesions were short and sterile, and seemed to be a physiological reaction from the plant. A second pathogenicity test was completed in 5 months beginning in June 2012. UCD105 was consistently re-isolated, and UCD102 and UCD103 were re-isolated in two out of three plants. The average lesion lengths for UCD102, UCD103, UCD105, and control plants were 2, 3, 5, and 1 mm, respectively. Compared to grapevine (Vitis vinifera), the pathogen grows more slowly in pear tissue under natural conditions. To our knowledge, this is the first report describing D. seriata as a causal agent of pear branch canker in California. Canker diseases can reduce the lifespan of perennial plants, ultimately leading to long term economic losses for growers (3).

FIELD EVALUATION OF ORGANICALLY ACCEPTABLE FOLIAR INSECTICIDES FOR CONTROL OF GREEH PEACH APHID, 2013

A field test was conducted to evaluate the efficacy of five organically acceptable foliar insecticides for the control of GPA on young (non-bearing) peach trees under New Mexico conditions. The trial was conducted in Apr, 2013, in a 0.12 ha block of peaches (planted in Mar, 2012), at the Los Lunas Agricultural Science Center, Los Lunas, NM. The experiment was conducted as a randomized complete block design with five single-tree replicates per treatment, using initial (pre-treatment) infestation levels as the blocking factor. A water-treated check was included. Aphid populations on the experimental trees were assessed by counting all individuals on the two apical leaves of five randomly selected shoots per tree. Pre-treatment counts were made on 25 Apr, 2013 and all applications were made between 8 and 10:20 am the following day using a 7.5 liter garden sprayer. Products, formulations and rates are listed in Table 1. All treatments were applied to run-off. Aphid populations were re-assessed at 1, 3 and 7 DAT using the same method as described above. The data were not normally distributed and could not be successfully transformed; they were therefore analyzed by Kruskal-Wallis non-parametric analysis of variance, followed, where appropriate, by pairwise between-treatment comparison using the Mann-Whitney procedure. All statistical analyses were conducted using Minitab® statistical software.

Development of single‐dispenser pheromone suppression of Epiphyas postvittana, Planotortrix octo and Ctenopseustis obliquana in New Zealand stone fruit orchards

Pheromones of two native leafrollers of economic importance to the New Zealand horticulture industry, Planotortrix octo [(Z)-8-tetradecenyl acetate and tetradecyl acetate] and Ctenopseustis obliquana [(Z)-5-tetradecenyl acetate and (Z)-8-tetradecenyl acetate], were reinvestigated and combined with pheromone of Epiphyas postvittana [light-brown apple moth, (E)-11-tetradecenyl actetate and (E, E)-9,11-tetradecen-1-yl acetate] to develop a single dispenser for mating disruption of three pest species for integrated pest management. Additional compounds identified from pheromone gland extracts were characterised as repellents for P. octo. However, for C. obliquana from Central Otago, a change in ratio of (Z)-5-tetradecenyl acetate and (Z)-8-tetradecenyl acetate and the addition of three compounds found in the gland (dodecyl acetate, tetradecyl acetate and hexadecanal) led to a significant improvement in catch over previous lures. Males from Central Otago showed antennal electrophysiological responses to hexadecanal, unlike C. obliquana from Auckland, which did not. Three multiple-species disruption blends were devised in a single dispenser to target E. postvittana, P. octo and C. obliquana. Disruption of traps was recorded in single-tree replicates with all three blends, but the five-component blend was overall most effective at disruption and was deployed area wide in commercial orchard plots. Deployment of single dispensers into commercial stone fruit orchards led to disruption of trapping for the three species and measurable reductions in insecticide use in cherries, peaches and nectarines without increased fruit damage (assessed in apricots).

Alternative Organic Fungicides for Apple Scab Management and Their Non-target Effects

A major challenge in organic apple production in humid production regions is the available fungicide options for apple scab [Venturia inaequalis (Cooke) Wint.] management. The standard sulfur/lime sulfur fungicide program can be injurious to the applicator, the apple ecosystem, and the apple tree itself. The objectives of this study were to compare the efficacy of three potential alternative fungicides [potassium bicarbonate (PB), neem oil (NO), and Bacillus subtilis (Bs)] with a standard organic sulfur/lime sulfur (SLS) fungicide program and a non-treated control (NTC) for management of apple scab and to evaluate potential non-target impacts on pest and beneficial arthropod populations. The five treatments were applied to ‘Empire’ trees arranged in a completely randomized design with five single-tree replications at the University of Vermont Horticultural Research Center in South Burlington, VT. Fungicides were applied with a handgun to drip using maximum label rates. Applications began on 26 Apr. 2007 and 23 Apr. 2008 and continued on approximately a weekly schedule through the end of June and then every 2 weeks through 23 July 2007 and 17 July 2008, respectively. The standard SLS treatment resulted in the best scab control in both years. The NO treatment reduced foliar and fruit scab compared with the NTC and the other alternatives at the end of the 2008 growing season and had insecticidal activity. However, both the SLS and NO treatments had disadvantages, including phytotoxic burning on the fruit and/or significantly more russeting on the fruit at harvest. In each year of the study, one or more of the alternative treatments, particularly Bs, resulted in higher insect damage than the non-fungicide-treated control. This research showed that PB, Bs, and NO do not offer advantages over the standard SLS fungicide program in organic apple production and in some cases offer distinct disadvantages in terms of non-target impacts. Chemical names used: potassium bicarbonate (Armicarb “O”), Bacillus subtilis (Serenade MAX), neem oil (Trilogy), sulfur (Microthiol Sulfur)/lime sulfur (Miller Lime Sulfur)

Microencapsulated Pear Ester Enhances Insecticide Efficacy in Walnuts for Codling Moth (Lepidoptera: Tortricidae) and Navel Orangeworm (Lepidoptera: Pyralidae)

The efficacy of combining insecticides with a microencapsulated formulation of ethyl (2E,4Z) -2,4-decadienoate (pear ester, PE-MEC) was evaluated in walnuts, Juglans regia L., for codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), and navel orangeworm, Amyelois transitella Walker (Lepidoptera, Pyralidae). Two types of studies were conducted to compare the use of insecticides with and without PE-MEC. In the first study, PE-MEC in combination with reduced rates of insecticides, including chlorpyrifos, phosmet, methoxyfenozide, and codling moth granulovirus were evaluated in single tree replicates. PE-MEC was tested at one to three rates (0.6, 1.8, and 4.4 g active ingredient ha(-1)) with each insecticide. In the second study, seasonal programs including sprays of esfenvalerate, chlorpyrifos, and ethyl parathion at full rates were evaluated in replicated two ha blocks. Significant reductions in nut injury occurred in the single-tree trial with treatments of PE-MEC plus insecticide compared with the insecticides used alone against both pest species; except with methoxyfenozide for navel orangeworm. Similarly, nut injury in the large plots was significantly reduced with the addition of PE-MEC, except for navel orangeworm in one of the two studies. These results suggest that adding pear ester as a microencapsulated spray can improve the efficacy of a range of insecticides for two key pests and foster the development of integrated pest management tactics with reduced insecticide use in walnut.

TIME OF ERGER APPLICATION FOR BUDBREAK INDUCTION IN APPLE TREES

More than 50% of the Southern Brazilian apple production is located in areas where chilling varies from 800 to 1.200 cold units by the North Carolina model, or from 400 to 600 hours of temperature below 7.2°C. This low chilling results in budbreak and blooming delay, which requires artificial budbreak induction. Erger, an inorganic nitrogen compound, combined with calcium nitrate, has a similar effect to that of hydrogen cyanamid, with the advantage of being less dangerous to the environment. Budbreaking products are influenced by environmental factors, but mainly by the temperature at the time of application or during the following days, which should be at least 20°C. The aim of this experiment was to evaluate the effects of time of Erger 5% + Calcium Nitrate 5% application on budbreak induction of 'Imperial Gala' and 'Suprema' apple trees. The experiment was carried out in Cacador, Brazil (lat. 26°46'31), in an RCB design with five treatments and six single tree replications. The treatments were a check and four fortnightly Erger applications. Phenology, axillary and terminal budbreak, fruit set, fruits per cluster and mean fruit weight were evaluated. In comparison with the check treatment, Erger 5% + calcium nitrate 5% anticipated up to 28 days the full bloom of 'Imperial Gala' when applied on August 15, but only up to 13 days if applied on September 15. The effect on 'Suprema' was at a lesser extent than on 'Imperial Gala'. The axillary's budburst of 'Imperial Gala' significantly increased when the plants were treated on August 1, differing from the check up to 60 days after application. The axillary's budbreak on 'Suprema' was greater than on the check trees except for the application on August 15 because of the low temperature that persisted also during the following days. The low temperature affected the response in both cultivars. Fruit set of 'Imperial Gala' was not affected by the time of treatment application, but it was reduced in 'Suprema' when applied on August 1. There was a tendency of mean fruit weight increase on treated plants, probably related to a longer bloom-ripening period.

A comparison of pod production and insect ratings of 12 elite Prosopis alba clones in a 5-year semi-arid Argentine field trial

Semi-arid adapted nitrogen fixing trees of the genus Prosopis have been extensively used in Argentina for soil improvement, luxury quality lumber production and sweet (35% sucrose) pods for humans and livestock. Due to the great demand of Prosopis alba for lumber, erect, tall, high pod producing trees of this species have been greatly overharvested, leading to erosion of the gene pool. A previous progeny trial with 57 half sib families identified 12 trees with promise for rapid growth, high production of pods and sweet pods. This trial, on a site with a salinity of 8.6 dS m −1 EC and a pH of 7.7, examined clones of these 12 trees in a randomized complete block trial with 8 single tree replications for height, basal diameter, canopy height and diameter, production of pods, sensory characteristics of the pods, disease resistance and insect resistance. In the 5th year of production and 7th year from planting, three clones produced more than 50 kg pods per tree versus 32 kg for check. At this 10 m × 10 m spacing, this yield of 5000 kg/ha compares favorably to many other semi-arid crops, especially given the unfavorable salinity and pH. In contrast to genetic improvement in pod production, the clones had lower diameter, height and canopy growth than the check. The lower biomass production may be due to fibrous root system produced from cuttings, since some of the clones blew over in high winds but none of the checks produced from seed blew over. Companion seed orchards of salt tolerant clones may provide rootstock for these high pod production clones. Significant differences in insect and disease resistance of the clones were observed and full sib crosses were made to study the genetics of the resistance. All clones had good sensory properties for use in human food. This is the first replicated trial with multipurpose clones useful for lumber and human food. The annual diameter growth rates ranged from 2.8 to 4.1 cm year −1 which was estimated to produce an internal return of approximately 20% from lumber alone.

LEAF AREA INDEX FOR FLAT SHAPE TRAINED LONGAN (DIMOCARPUS LONGAN LOUR.) TREES TO IMPROVE FRUIT QUALITY AND YIELD

The using of leaf area index (LAI) in order to improve yield and fruit quality of longan was conducted in two experiments. The first experiment was performed in 6-year-old flat shape trained 'Daw' longan trees from September 2005 to July 2006. The treatments were a) defoliation of old leaves at 20% of the whole tree, b) defoliation at 40%, c) defoliation at 60%, and d) no defoliation (control), with four single tree replicates, applied at 60 days after anthesis. After harvest, the results showed that the fruit yield of all the treatments gave no significant differences, but the defoliation treatments at 40 and 60% gave extra large fruit percentages of 50.65 and 50.94%, respectively, which were higher than the control trees (30.93%), and the 20% defoliation (33.90%). In addition, the LAI of the control trees and the 20% defoliation trees were 6.27 and 5.31, respectively, which were significantly higher than the 40 and 60% defoliation, 3.49 and 2.47 respectively. In the second experiment LAI at 2 and 3 (by defoliation of old leaves) compared with control trees, LAI at about 7. This experiment used four flat shape 5-year-old 'Daw' longan tree replicates, conducted from August 2006 to February 2007. After harvest, the results showed that the yield, the seed size and weight, the pericarp weight and thickness, and the fruit total soluble solids gave no significant differences among the treatments. But the aril weight and the aril recovery percentages of the trees with LAI at 2 and 3 were significantly higher than the control trees. In addition, the fruit weight, the fruit size, and the aril thickness of the trees with LAI at 3 were significantly higher than the control trees, but showed no significant differences to the trees with LAI at 2.

INTENSIDAD DE PODA SOBRE EL VIGOR, PRODUCCIÓN Y PESO DEL FRUTO, DEL MANGO 'ATAULFO'

Pruning is an essential practice to maintain the productivity in mango orchards. However, this labor is an uncommon practice in Nayarit, Mexico. Until now, it is unknown the more suitable pruning intensity to control the tree size and to get the best yields. The objective of this study was to evaluate the effect of pruning intensity on vigor, yield and weight fruit of ‘Ataulfo’ mangos. Three pruning intensities were evaluated, consisting of pruning at 50, 75 or 100 cm of all the shoots around the tree canopy. A control without pruning was also included. A completely randomized experimental design with 10 single tree replications was used. The main variables were vigor, yield and fruit weight. After the first year of evaluation, it was found that pruning facilitated to control the tree size since pruned trees had 10 % less height and 14 % less canopy diameter than unpruned trees. Pruned trees with 100 cm had the highest vegetative growth and the new shoot were longer with 31 cm; but the flowering in the immediately year after the pruning was the lowest with 16.50 %. Pruning intensity did not affected annual or accumulated yield of two years. In addition, it was noticed that any of the pruning intensities affected the fruit weight.

EVALUATION OF POTENTIAL ALTERNATIVE EUROPEAN PEAR CULTIVARS FOR U.S. WEST COAST GROWERS

EVALUATION OF POTENTIAL ALTERNATIVE EUROPEAN PEAR CULTIVARS FOR U.S. WEST COAST GROWERS

GROWTH AND FRUITING CHARACTERISTICS OF EIGHT APPLE GENOTYPES ASSESSED AS UNPRUNED TREES ON 'M.9' ROOTSTOCK AND AS OWN-ROOTED TREES IN SOUTHERN FRANCE

ISHS VIII International Symposium on Canopy, Rootstocks and Environmental Physiology in Orchard Systems GROWTH AND FRUITING CHARACTERISTICS OF EIGHT APPLE GENOTYPES ASSESSED AS UNPRUNED TREES ON 'M.9' ROOTSTOCK AND AS OWN-ROOTED TREES IN SOUTHERN FRANCE

PERFORMANCE OF PAWPAW CULTIVARS IN SOUTH CAROLINA

A field planting of 18 selections and 10 named cultivars of pawpaw (Asimina triloba) was established in November 1996 near Clemson, S.C., as part of the Pawpaw Regional Variety Trial coordinated by Kentucky State University. Trees were planted at 2.0 × 5.5 m spacing with drip irrigation and straw mulch in a randomized complete block design consisting of 8 single-tree replications. Data collected through 2005 included tree survival, total tree yield, and yield and average weight of fruit weighing >150 g. Since the start of the trial, 3 selections, 1-7-1, 11-5 and 8-58 have been named and released as `Shenandoah', `Susquehanna' and `Rappahannock', respectively. The highest yielding cultivars were `Shenandoah', `Rappahannock', and `PA-Golden'. The cultivars with the largest percentage of large fruit were `Shenandoah' and `Susquehanna'. `Middletown', `Mitchell', `Rappahannock', `Taytwo', `Wells' and `Wilson' produced the largest percentage of small fruit (<150 g). After 9 years, 66% of the original trees (i.e., scions) were alive. `Rappahannock', `PA-Golden', `Sunflower' and `Wilson' had either one or zero trees die, whereas `Middleton' and `Wells' had only 2 trees alive. Among the selections, 2-54, 9-58, 11-13, 1-68, 3-11, and 8–20 had either 88% or 100% survival. The highest yielding selections were 10-35, 1-7-2, 1-68, and 2-10, and 1-7-2, 2-10, 4-2, and 5-5 produced the highest percent of large fruit. Fruit quality characters such as aroma, flavor, aftertaste and texture were not quantified or evaluated.

Nitrogen Uptake in a Range of Alternative Orchard Floor Management Systems

The percentage of N from fertilizer removed from the field by fruit trees is low. Overapplication of N in orchards has been a common practice and is a concern due to environmental and tree growth problems caused by excess N. Orchard floor management practices (OFMP) can improve the physical and chemical properties of the soil and may alter the soil biological community. Biological activity can affect mineralization rate and thus nutrient availability. The purpose of this study was to determine the effect of alternative OFMP on fertilizer N uptake. Research plots were located in Corvallis, Ore. (COR) (7-year-old `Fuji'), and Hood River, Ore. (HR) (3-year-old `Red Delicious'). Treatments were begun in 2001 in a split-plot completely randomized design with three replications. Main plot treatments were herbicide or cultivation. Subplot treatments were no amendment, bark mulch, compost, and barley/vetch mown and blown into the tree row. Depleted NH3SO4 was applied to single-tree replicates at budbreak. Trees were destructively harvested at harvest of 2003. At HR, the percentage of N derived from fertilizer (NDFF) was significantly lower in the whole tree, leaves, new wood, old wood, spurs, and roots of trees from compost than from unamended plots (P < 0.05). At COR, the NDFF in the leaves, fruit, new wood, spurs and roots was significantly lower in trees from compost plots than unamended plots (P < 0.05). The NDFF also tended to be lower in trees from bark mulch-treated plots than control plots, although differences were not always significant. Vetch/barley amendment resulted in NDFF similar to no amendment. There were no significant differences between the total N of trees from unamended and compost plots. Trees from compost-treated plots appear to be acquiring N from sources other than fertilizer.