Green Tip Research Articles

Modeling apple bloom phenology

Detailed information about apple phenology allows a grower to manage the orchard efficiently and to decide how many fruits per tree harvest. In general, eight stages have been identified for apple development starting with green tip until petal fall. Mathematical models can be developed to predict crop phenological stages. The objective of this study was to model apple phenology as a function of the physiological time using cumulative degree days (GDD). The cultivars 'Cripps Pink', 'Gala', and 'Red Delicious' were monitored twice weekly during four growing seasons for eleven different locations in the main apple growing regions of eastern Washington. Thirty buds were selected and the number of buds at a particular stage was registered. Daily temperature data came from the closest automated weather station of AgWeatherNet to the orchard where the samples were collected. The field observations showed that the stages were not mutually exclusive with at least two stages overlapping during apple development. The approach for the model was based on the duration or accumulation of GDDs for each individual stage from the first to the last observation of each stage. To determine GDD, the base temperature, i.e. 6.11°C was subtracted from the average temperature. For each stage, the lower and upper limits for the duration were calculated as the average of the minimum and the maximum GDDs for each stage. A comparison of the stage distribution among seasons, cultivars, locations and their interactions was conducted using GLIMMIX SAS procedure. There was significant effect of the factors and their interactions, indicating the complexity of apple development. The duration of each phenological stage was similar for all of the cultivars however cultivar 'Gala' started later than the other two cultivars for each stage. The model performance was good. A prototype of the model will be implemented on the AgWeatherNet portal (www.weather.wsu.edu).

Variation in the flowering phenology of apple and pear in Australia

Bud burst and flowering dates of commercial apple and pear cultivars were monitored in three geographically and climatically distinct growing regions of Australia (Applethorpe, Queensland; Shepparton, Victoria; Manjimup, Western Australia). Whole tree field assessments were made of 5% green tip, first open flower and progression of flowering to full bloom at all sites. Initial data from 2012 and 2013 indicated significant regional and varietal variation in the timing of bud burst and flowering. Variability in the duration of the period between first open flower and full bloom among sites suggests potential effects of climate on the consistency of flowering. Relationships between phenological variability and temperature are discussed. Field measurements and temperature data are being used to develop cultivar specific models of bud burst and flowering time. These phenological models will be used in conjunction with 2030 climate forecasts to make predictions about potential impacts on the pome fruit industry in Australia. Preliminary results from the modelling analysis are presented.

Cane pruning on Chardonnay grapevine in the high-altitude regions of Southern Brazil

High-altitude regions of southern Brazil, located above 900 m above sea level, the cordon training with spur pruning is widely used because of easier application. In these regions, Chardonnay wine grape shows potential to produce quality wines, however, in commercial vineyards, the training system used has not provided productivities that makes economically viable the cultivation of this variety. Given this, the present study aimed to evaluate the effect of different cane-pruning systems on the vegetative, productive and enological potential of Chardonnay grapevines grown in the high-altitude region of Southern Brazil. The experiment was conducted in a commercial Chardonnay vineyard, located in Sao Joaquim – Santa Catarina State (28o 17 ′39”S and 49∘ 55′56” W, to 1230 m a.s.l) during 2015 and 2016 vintages. Chardonnay vines (grafted on 1103 Paulsen) were planted in 2010, with a 3.0 m (row) × 1.0 m (vine) spacing. The treatments consisted of different cane-pruning systems: Cordon spur-pruning (control); Sylvoz; Cazenave; Capovolto; single Guyot and double Guyot. Pruning was performed in August of each year when the buds were in the green tip developmental stage. Data was analyzed by Scott Knott test (p g−1 grape at 2016 vintage. Commercial maturity of grapes (soluble solids, acidity and polyphenols) did not differ among training systems studied. The results suggest that cane-pruning systems could be an alternative to increase production efficiency of Chardonnay in high-altitude region of southern Brazil.

The use and mechanism of NO to prevent frost damage to flower of apricot

Apricot production is mostly located in areas of Iran, where flowering is damaged by temperatures. Using plant growth regulators to decrease spring frost damage is suggested as a measure to avoid frost damage. The objective of this study was to determine the effects of nitric oxide treatment on avoiding spring frost damage apricot. We evaluated applications of nitric oxide (NO) 0 (control, water only), 10 and 15μM at green tip and pink tip stages of ‘Thokhm Gerdi’ apricot then treated shoots were collected and cutting sections were placed in incubator and subjected to sequential freezing temperature, −1, and −3°C, held for 30min at each temperature. The NO treatment decreased freezing injury, lipid peroxidation and ion leakage percentage for flowers after freezing tests at treatment both stages (especially pink tip stage and −3°C) compared with control. The results showed No application increased significantly proline, inducing sugar, ascorbate peroxidase, superoxide dismutase, catalase, peroxidase enzyme activity and DPPH-radical scavenging activity of flowers. These results showed that NO affects antioxidant capacity of flowers and changes solute content (proline, inducing sugar). Moreover, NO treatment protects apricot flowers from freezing and spring frost damage. So, the present study is the first evidence that nitric oxide effects on avoiding spring frost damage of apricot.

Evaluation of Dormant-Stage Inoculum Sanitation as a Component of a Fire Blight Management Program for Fresh-Market Bartlett Pear.

From 2010 to 2013, the efficacy of copper-based inoculum sanitation as a component of fire blight management programs was evaluated in commercial pear orchards located in northern California. Forty-one 4-ha sections of orchard were split into two equal-sized plots, with the orchardist applying horticultural oil alone to one plot and horticultural oil plus a fixed copper bactericide to the other plot. These treatments were timed to begin just prior to and finish at the "green tip" phenological stage, which occurs about 5 weeks before full bloom. During bloom, flower samples were collected from the plots and subjected to a loop-mediated isothermal DNA amplification (LAMP) assay for specific detection of Erwinia amylovora. Overall, epiphytic populations of E. amylovora on flowers were detected rarely at midbloom (6% of samples) but commonly at petal fall (44% of samples). In three of four seasons, E. amylovora detection in flower samples at a given bloom stage was significantly suppressed in copper-plus-oil-treated plots compared with oil-only plots. All orchards also received antibiotic treatments during the bloom period and, perhaps as a consequence, the development of fire blight was sporadic and not affected significantly by the copper treatment in any season. The pathogen detection data indicate that copper sanitation may add value to a fire blight management program by delaying the increase of epiphytic populations of E. amylovora in flowers to the late stages of the bloom period, at which time the number of susceptible flowers declines rapidly.

Role of methyl jasmonate and salicylic acid applications on bloom delay, flowering and fruiting of ‘Elberta’ Peach

Peach (Prunus persica L. Batsch.) is produced in most areas of Iran, where flowering is hindered by temperature. Using plant growth regulators to delay bloom is a suggestive measure to avoid frost damage. The objective of this study was to determine the effects of methyl jasmonate (MJ) and salicylic acid (SA) on peach bloom delay and yield. This study evaluated the applications of MJ 0 (control, water only), 100 and 200 mg L-1 and SA at 150 and 300 mg L-1 at swollen bud and green tip stages. In ‘Elberta’ peach, MJ at 200 mg L-1, its combinations with SA at 150 mg L-1 and MJ 200 mg L-1 and SA300 mg L-1 together at the two stages (green tip, swollen bud stages) delayed blooming for 6 and 8 days, respectively. The maturity and ripening of treated peach fruits were delayed for 8-12 days in green tip and swollen bud stage. Flowering percentage amount (57.83-61.80%), fruit set amount (22.59-23.53%) and yield (1.69-1.72 kg cm-2 branch) were increased by MJ 200 mg L-1 and SA300 mg L-1 treatments compared to the control treatment (flowering percentage amount (39.31%), fruit set amount (6.25%) and yield (0.82 kg cm-2 branch). The interactions of MJ and SA had more impacts on flowering (89.53%), fruit set (33.22%), fruit weight average (124.93 g), and yield (2.09 kg cm-2 branch)compared to their individual application. The present study was the first evidence for the SA and MJ effect on bloom delay, flowering and fruiting of peach.

Disease and pest management in apple: Farmers' perception and adoption in J&K state

Diseases and pests are one of the limiting factors for low productivity of the fruit crops in Kashmir valley, India. A study on management of resources with respect to disease and pest management of apple and extent of adoption of recommended plant protection technology was undertaken for increasing apple production in Kashmir valley of J and K State. District Baramulla was selected purposively on the basis of maximum area and production under apple crop. A sample size of 200 apple growers 50 each from 4 villages were selected randomly. The study revealed that the perception index regarding attributes of technology recommended in two diseases viz. San Jose Scale and Apple Scab was 68.88% and 80.76% in respect of profitability (83.97%), simplicity-complexity each 63.57% and 54.27 % for practicability attributes of technology. The data further showed that the farmers adoption level under Chemical control was high at silver tip to green tip stage (80%) and fruit let pea size stage (78%) and medium adoption was observed at pink bloom (bud) stage (74%), petal fall stage (74%) walnut size apple stage (70%) on Apple Scab similarly, the extent of adoption was low (45%) for mechanical and no chemical control measures under clean cultivation. In case of San Jose Scale the farmers adoption level regarding name of chemical, its dose, quantity of water required per acre for preparing spray solution and time of spray at late dormant spray, (feb, March) was high (80%). The findings will help to improve the level of farmers’ knowledge to increase apple production in Kashmir valley.

Spring frost vulnerability of sweet cherries under controlled conditions.

Spring frost is a significant production hazard in nearly all temperate fruit-growing regions. Sweet cherries are among the first fruit varieties starting their development in spring and therefore highly susceptible to late frost. Temperatures at which injuries are likely to occur are widely published, but their origin and determination methods are not well documented. In this study, a standardized method was used to investigate critical frost temperatures for the sweet cherry cultivar 'Summit' under controlled conditions. Twigs were sampled at four development stages ("side green," "green tip," "open cluster," "full bloom") and subjected to three frost temperatures (-2.5, -5.0, -10.0°C). The main advantage of this method, compared to other approaches, was that the exposition period and the time interval required to reach the target temperature were always constant (2h). Furthermore, then, the twigs were placed in a climate chamber until full bloom, before the examination of the flowers and not further developed buds started. For the first two sampling stages (side green, green tip), the number of buds found in open cluster, "first white," and full bloom at the evaluation date decreased with the strength of the frost treatment. The flower organs showed different levels of cold hardiness and became more vulnerable in more advanced development stages. In this paper, we developed four empirical functions which allow calculating possible frost damages on sweet cherry buds or flowers at the investigated development stages. These equations can help farmers to estimate possible frost damages on cherry buds due to frost events. However, it is necessary to validate the critical temperatures obtained in laboratory with some field observations.

HIGH DENSITY ORCHARD PRODUCTIVITY OF THE NEW 'KALEI' SCAB-RESISTANT APPLE

‘Kalei’ is a new high quality scab-resistant red apple developed in Queensland, Australia. Fruit mature two weeks before ‘Pink Lady’(TM), and are sweet, crisp and juicy. Consumer testing of ‘Kalei’ apples and assessment of the productivity of ‘Kalei’ trees in a range of orchard systems were two primary components of the evaluation process that provided the confidence to release this cultivar in 2012. This paper reports on two experiments conducted at Applethorpe Research Station (28°37’S) in southern Queensland, to measure the orchard productivity of ‘Kalei’. Trees on M.9, MM.102, M.26 and MM.106 rootstocks planted at 2,500 trees/ha yielded 70-80 t/ha in their 8th leaf in 2012, with >90% packouts of first grade fruit. The yield of ‘Kalei’ trees in open V trellis systems reached 115-140 t/ha in 2012 (8th leaf), with packouts of first grade fruit above 95%. The semi-spur habit of ‘Kalei’ trees is easy to manage, and aids fruit colour development. The potential yields of trees in their 6th and 7th leaf were reduced by severe dust storms. ‘Kalei’ can be an excessively large apple (>200 g) if trees are under-cropped. No sprays for apple scab control (except for green tip copper) have been applied since planting, and ‘Kalei’ trees continue to show no leaf or fruit symptoms of apple scab.

Behavior of European pear cultivars to floral bud necrosis in southern Brazil

The pear crop offers an expansive market opportunity in southern Brazil, because of suitable climatic conditions and available infrastructure. However, there are still some barriers that prevent satisfactory economic production. Floral bud necrosis (FBN) is one of the main problems afflicting pear orchards in southern Brazil. FBN is characterized by the occurrence of necrosis in the flower primordia of floral buds decreasing the crop yield potential. The objective of this work was to evaluate the behavior of European pear cultivars (Clapp's Favourite, Conference, Packham's Triumph, Rocha, Abate Fetel, Santa Maria, Decana and William's) grafted on quince rootstocks (Adams, EMA and EMC) to FBN susceptibility in two different phenological stages (vegetative dormancy and green tip) and two different edaphoclimatic regions (Fraiburgo/SC and Urupema/SC) of southern Brazil during the 2009/2010 and 2010/2011 growing seasons. Twenty floral buds at both phenological stages of vegetative dormancy and green tip were collected in 10 randomized plants per plot in each region. The floral buds were assessed by microscope following the symptomatic scale of: 1. Floral buds with absence of necrosis; 2. Floral buds with partial necrosis and, 3. Floral buds with total necrosis. The combinations Conference/Adams and Packham's Triumph/EMA and the combination Abate Fetel/Adams showed the highest severity of floral bud necrosis in both phenological stages evaluated in the region of Fraiburgo/SC and Urupema/SC, respectively. The Clapp's Favourite/EMA and Conference/EMC combinations significantly showed the lowest severity of FBN in both the phenological stages of vegetative dormancy and green tip in both regions of Fraiburgo/SC and Urupema/SC, in the edaphoclimatic conditions of southern Brazil during the 2009/2010 and 2010/2011 growing seasons.

Seasonal changes of physiological parameters in sweet cherry (Prunus avium L.) buds

Studies concerning chilling requirements of sweet cherry are of great importance to improve phenological models on the base of plant physiological processes. Mainly the release of dormancy is still a black box in phenological modelling. From an economical point of view, sweet cherries are one of the most interesting fruits, but information about the relationship between dormancy, growth and development of flower buds under the climatic conditions of the North Eastern Germany are scarce. The presented 2 year results are to our knowledge the first under natural conditions in fruit tree orchards with a high temporal resolution during the dormant stage (October) until cluster development (April). We investigated changes in sweet cherry buds of ‘Summit’ with respect to fresh and dry weight, water content, C- and N/15N content, abscisic acid (ABA), an ABA-isomer, sugars, carotenoids, and free amino acids (asparagine, aspartic acid, isoleucine) in 2011/2012 and 2012/2013.The transition from dormant stage to the beginning of growth was first obvious by markedly changes of the water content. The phase from green tip to tight cluster, with a length of only 4 days, was the period of the most physiological activity in single buds, because of the highest daily accumulation rates of fresh/dry weight, C, N. We assume a concentration dependant regulation of the member of the aspartate family (asparagine, aspartic acid, isoleucine) during dormancy, growth and development in sweet cherry buds. The ABA content showed 2011/12 a clear bimodal pattern which was at lower level similar in 2012/13, but not so strong incisive. In both years, the first peak was probably related to the end of endodormancy. However the ABA-isomer content showed in both seasons a unimodal pattern. The maximum of the ratio of ABA-isomer/ABA indicated the beginning of ontogenetic development which starts 3 and 2 weeks later, respectively. Our results suggest that ABA and the ABA-isomer in the sweet cherry buds regulate differentiated metabolic processes in the dormant stage and during bud growth and development. After replication in the season 2013/14 the estimated dates of release of endodormancy, beginning of ecodormancy and start of ontogenetic development will be used to validate and improve phenological models for the beginning of cherry blossom.

Germplasm Collection and Diversity Analysis in Yardlong Bean (Vigna unguiculatasubsp.sesquipedalis) from Coastal Andhra Pradesh and Odisha

Diversity in yardlong bean (Vigna unguiculata subsp. sesquipedalis), an under-utilized vegetable legume was collected from parts of North coastal Andhra Pradesh (Srikakulam and Viziznagaram districts) and adjoining regions of Odisha (Koraput and Gajapati districts). Substantial variation was observed among the 39 accessions collected. Most of collections had pods which were light green (28), some were light green with purple tip (6), and a few were dark green (4); one accession (IC582551, Jeypore, Koraput, Odisha) had purple pods with green tip. Variation in pod length ranged from 24–75 cm; fresh pod weight (10 pods) from 60–140 g and seeds/pod from 6.2–17. Pod length had the highest dispersion index (158%), followed by100-seed weight (127%), fresh pod weight (89%) and seeds/pod (83%). Accessions IC582850 and IC582863 had the longest pods (75 cm). A pure line selection from IC582850 (Jeypore, Odisha) is released for cultivation as ‘Arka Mangala’. This pole type, photo-insensitive variety with green, smooth pods and a crop duration of 3–4 months recorded a pod yield of 25.7 t/ha with an increase of 24% and 30% pod yield over the check varieties ‘Lola’ and ‘Vyjayanthi’, respectively.

Determination of effective moisture diffusivity and assessment of quality attributes of banana slices during drying

The influence of drying temperatures on the moisture diffusivity and quality attributes of the dried banana slices in terms of volatile compound, shrinkage, color, texture and microstructure were studied. Bananas with peel color index of 5 corresponding to yellow color with green tip were sliced into 3 mm thickness, dipped into ascorbic acid solution and dried at four temperatures of 70, 80, 90 and 100 °C. Drying rate of banana slices can be divided into two sub-drying periods, first and second falling rate periods. The effective diffusivity estimated by the optimization technique was found to decrease sharply with moisture content in the first falling rate period and changed slightly in the second falling rate period. High-temperature drying seems to provide lower loss of volatile compounds in the dried sample. Moreover, the dried banana was very porous, resulting in remarkably lower hardness value than that obtained from the low-temperature drying whilst the crispiness was not significantly different amongst the samples obtained at various drying temperatures. Although the textural property could be improved at high temperature, the product color was brown as manifested by the low L- and hue values in particular at the drying temperature of 100 °C.

Introducing Bacillus licheniformis as the causal agent of pistachio dieback in Iran

During 2004 and 2006 growing seasons some pistachio trees in Kerman province of Iran showed dieback symptoms. Initial symptoms were observed at the beginning of the growing season and they developed during two weeks after green tip stage, as shoot tips turned black and dieback occurred. During the growing season, the symptoms developed and vessel destruction was observed. If these stems were not pruned during winter, dieback developed in the spring. During the growing season affected pistachio samples were collected and surface disinfected with 0.01% mercury chloride. Pieces of affected vessels were grown on nutrient agar (NA) and incubated at 25°C for three-to-four days. Bacterial colonies with Bacillus characteristics were isolated and 15 representative strains were selected for further characterisation. The pathogenicity of selected strains was verified on 2–3 year-old pistachio seedlings using injection of bacterial suspension (107 cfu p/ml) and control plants inoculated with distilled water; vessel destruction developed after 20 days, and bacterial causal agent was isolated from seedlings. No symptoms were observed in control plants. The strains were Gram positive, motile, with central spores and caused a hypersensitivity reaction (HR) on tobacco and geranium; they were positive for anaerobic growth, nitrate reduction, utilisation of citrate, VP test, urease, catalase, growth at pH 5.7, 7% NaCl and 45°C, acid production from arabinose, xylose, glucose and mannitol, and anaerobic fermentation of glucose. They could hydrolyze starch, aesculin, Tween 80 and gelatin but indole production was negative. Based on the characteristics of the isolated strains, they were identified as Bacillus licheniformis. This is the first report of Bacillus licheniformis as a causal agent of pistachio dieback.

Estimation of Chilling and Heat Requirements of Some Persian Walnut Cultivars and Genotypes

The objective of this work was to determine the chilling and heat requirements of Persian walnut cultivars and genotypes using excised twigs. The experiment was carried out from Nov. 2006 and 2007 to Mar. 2007 and 2008. One-year-old twigs were prepared from four cultivars and four domestic genotypes of Juglans regia L. After leaf fall, the twigs were taken and placed in plastic bags and kept at 4 ± 1 °C to stimulate 400 to 1500 chilling hours. After chilling, the excised twigs were transferred to the greenhouse with a natural photoperiod and a temperature from 18 to 27 °C. The evaluation of budbreak was made three times a week and the number of accumulated growing degree hours (°C) was determined until the buds reached the balloon or green tip stage. The chilling requirements were lowest (400 h) for catkins and highest (1000 h) for lateral buds. The Serr cultivar and ‘Z30’ genotype had the lowest chilling requirements (650 and 650 h). ‘Lara’, ‘Z63’, ‘Z53’, ‘Pedro’, and ‘Z67’ showed intermediate chilling requirements with values of 900, 900, 800, 750, and 750 h, respectively. Finally, ‘Hartley’ completed its dormancy after an accumulation of 1000 h, being the walnut cultivar with the highest chilling requirement in our study. As the final result, the cultivars and genotypes were classified into three groups based on their heat requirements: low requirement (‘Z30’ and ‘Serr’), medium requirement (‘Z53’, ‘Z67’, ‘Lara’, and ‘Pedro’), and high requirement (‘Hartley’ and ‘Z63’).

Role of organosilicone surfactant in apple scab control under scab conducive weather conditions

Fungicides of integrated fruit production (dithianon, captan, and diclofluanid) and an organosilicone surfactant were compared in spray schedules from green tip until summer in order to control apple scab caused by Venturia inaequalis and to evaluate their phytotoxicity on fruit. Sixteen sprays of 1.8 kg ha-1captan, 0.41 ha-1 dithianon, and 1.8 kg ha-1 diclolfluanid significantly (P=0.05) reduced the incidence of leaf or fruit scab compared to unsprayed products. All fungicides applied with organosilicone at 0.1% resulted in lower incidence of scab on young and older leaves as well as on harvested fruit, but these were not statistically always better than fungicides applied alone. In case of diclofluanid, the fungicide applied with organosilicone at 0.1% resulted in significantly lower (P = 0.001) incidence of scab on young and older leaves. Diclofluanid applied with organosilicone at 0.1% gave the best scab control on leaf and fruit. Treatments applied with fungicides alone had no significant effect on plant phytotoxicity compared to untreated control. All fungicides applied with organosilicone at 0.1% increased (P = 0.05) fruit damage compared to untreated control or fungicide applied alone, though these were not always significantly different. In case of percentage of fruit russet, treatment of dithianon 0.4 1/ha + 0.1% organosilicone significantly increased fruit russet, while fruit russet index significantly increased in the treatment of diclofluanid 1.8 kg/ha + 0.1% organosilicone compared to untreated control. In sum, application of surfactants can help to increase efficacy of scab fungicides; and consequently, to reduce the risk of fungus infection under high scab disease pressure. This fact may also be helpful in fungicide resistance management and reduced-spray programs with accurate scab warning systems.

Nuclear, chloroplast, and mitochondrial transcript abundance along a maize leaf developmental gradient

In maize, the chloroplast chromosome encodes 104 genes whose roles are primarily in photosynthesis and gene expression. The 2,000-3,000 nuclear gene products that localize to plastids are required both to encode and regulate plastid gene expression as well as to underpin each aspect of plastid physiology and development. We used a new "three-genome" maize biogenesis cDNA microarray to track abundance changes in nuclear, chloroplast and mitochondrial transcripts in stage 2 semi-emerged leaf blades of one month-old maize plants. We report the detection and quantification of 433 nuclear, 62 chloroplast, and 27 mitochondrial transcripts, with the majority of the nuclear transcripts predicted or known to encode plastid proteins. The data were analyzed as ratios of expression of individual transcripts in the green tip (mature chloroplasts) versus the yellow base of the leaf (etioplasts). According to the microarray data at least 51 plastid genes and 121 nuclear genes are expressed at least two-fold higher in the tip of the leaf. Almost all (25) mitochondrial and 177 nuclear transcripts were expressed at least 2-fold higher in the leaf base. Independent quantification of a subset of each transcript population by RNA gel blot analysis and/or quantitative real time RT-PCR concurred with the transcript ratios determined by the array. Ontological distribution of the transcripts suggests that photosynthesis-related RNAs were most highly abundant in the leaf tip and that energy use genes were most highly expressed in the base. Transcripts whose products are used in plastid translation constituted the largest single ontological group with relatively equal numbers of genes in the three expression categories, defined as higher in tip, higher in base, or equally expressed in tip and base.

Effects of three esca-associated fungi on Vitis vinifera L.: II. Characterization of biomolecules in xylem sap and leaves of healthy and diseased vines

Secondary metabolites and host defense compounds were shown to occur in xylem sap, and leaves of Vitis vinifera cv. Italia and cv. Matilde naturally infected by the esca-associated fungi Phaeomoniella chlamydospora ( Pch), Togninia minima ( Tmi) and Fomitiporia mediterranea ( Fme). Samples of xylem sap and leaves were collected from healthy vines and from vines showing severe symptoms of brown wood-streaking caused by Pch and Tmi, or from vines with symptoms of both brown wood-streaking and white rot caused by Fme. Xylem sap collection was carried out during the early spring of 2003 and 2004, corresponding to the phenological phases: (A) cotton bud; (B) green tip; (C) leaves out; (D) stretched out leaves; and (E) visible clusters. In the present work we have studied the accumulation of biomolecules (pentaketides and α-glucans), host defense compounds (benzaldehydes, benzoic acid and cinnamic acid derivatives, flavonols, flavanols, flavan-3-ol derivatives and stilbenes) at different stages of grapevine development. Accumulation and changes in total phenolics and recurring phenolics, and of three phytotoxic secondary metabolites (scytalone, isosclerone and pullulan) were analyzed by HPLC. On comparing results for cv. Italia and cv. Matilde, it can be seen that phenolic concentrations are strongly related to the cv.

The Effect of Surround WP on Apple Productivity and Fruit Quality in a Vermont Apple Orchard

Surround WP, a kaolin clay-based biopesticide product, is a potential alternative to some organophosphates used in apple orchards for the management of pests, such as codling moth. In addition, Surround has been reported to have important nontarget horticultural impacts because of its effect on canopy temperature reduction. The label for use of Surround states: “When applied at recommended rates and frequencies, benefits such as increased plant vigor and improved yields may occur in certain apple cultivars.” However, most of the research on nontarget effects has been conducted in warmer, semiarid environments. The objectives of this 3-year (2002–04) interdisciplinary research project were to determine potential nontarget effects of Surround WP application on apple tree vigor, productivity, and fruit quality in the relatively cool and moist climate of the Northeast. The research was conducted at the UVM Horticultural Research Center in South Burlington, Vt., on `McIntosh'/M26 trees. The experiment used a completely randomized design with five treatments replicated six times. Each replicate consisted of single tree plots. Treatments included: 1) Surround beginning at green tip plus fungicides; 2) Surround beginning at green tip without fungicides; 3) Surround beginning at petal fall plus fungicides; 4) standard IPM; and 5) nontreated control. Results indicate no significant differences among treatments 1, 3, and 4 (treatments that included fungicide applications) in vegetative shoot length, spur characteristics, blossom number, fruit weight, firmness, soluble solids, and fruit calcium levels. Trees treated with Surround had significantly lower yield efficiencies in 2003 and 2004 than trees under IPM treatment.

A Comparison of Methods Used to Estimate the Maturity and Release of Ascospores of Venturia inaequalis.

Maturation and release of ascospores of Venturia inaequalis were assessed at Geneva and Highland, NY, and at Durham, NH, by microscopic examination of crushed pseudothecia excised from infected apple leaves that were collected weekly from orchards (squash mounts) in 14 siteyear combinations. Airborne ascospore dose was monitored at each location in each year of the study by volumetric spore traps. Additional laboratory assessments were made at Geneva to quantify release from infected leaf segments upon wetting (discharge tests). Finally, ascospore maturity was estimated for each location using a degree-day model developed in an earlier study. Ascospore maturation and release determined by squash mounts and discharge tests lagged significantly behind cumulative ascospore release as measured by volumetric spore traps in the field. The mean date of 98% ascospore discharge as determined by squash mounts or discharge tests occurred from 23 to 28 days after the mean date on which 98% cumulative ascospore release had been detected by volumetric traps. In contrast, cumulative ascospore maturity estimated by the degree-day model was highly correlated (r2 = 0.82) with observed cumulative ascospore release as monitored by the volumetric traps. Although large differences between predicted maturity and observed discharge were common during the exponential phase of ascospore development, the date of 98% cumulative ascospore maturity predicted by the model was generally within 1 to 9 calendar days of the date of 98% cumulative ascospore recovery in the volumetric traps. Cumulative ascospore discharge as monitored by the volumetric traps always exceeded 98% at 600 degree days (base = 0°C) after green tip. Estimating the relative quantity of primary inoculum indirectly by means of a degree-day model was more closely aligned with observed ascospore release, as measured by volumetric traps, than actual assessments of ascospore maturity and discharge obtained through squash mounts and discharge tests. The degree-day model, therefore, may be a more accurate predictor of ascospore depletion than squash mounts or discharged tests, and has the added advantage that it can be widely applied to generate site-specific estimates of ascospore maturity for any location where daily temperature data are available.