Ursache des Triebsterbens an Heidelbeeren in Norddeutschland: Schadpilze oder Winterfrost?

In the summer of 2010 and during the following two seasons, a twig dieback of blueberries (Vaccinium corymbosum) was observed in southern Lower Saxony especially in younger plantations of the variety ‘Duke’. The sudden onset of a chlorosis and necrosis of individual twigs was associated with a destruction of the vascular cambium and with longitudinal streaks of brown discolourations in the xylem tissue deposited during the previous year. New shoots were often formed from the intact roots and from regions of older twigs located immediately above the soil surface. Potentially pathogenic fungi, including Godronia cassandrae, Phomopsis spp., Diplodia seriata, Pestalotiopsis sp., Paraconiothyrium sporulosum, Colletotrichum acutatum, Fusarium avenaceum and F. lateritium, were found sporadically on dead twigs, each fungus being present in 6 or fewer of the 12 plantations surveyed. Winter frost damage of xylem tissues was determined to be the main cause of the disease, facilitated by a delayed termination of vegetative growth which led to a lack of winter hardiness at the time-point of the first serious frost events.     

The impact of soil compaction on soil aeration and fine root density of Quercus palustris

The soil around Quercus palustris trees, 30 cm (11.8 in) average diameter breast height (DBH) were treated by compaction (C) or C plus clay slurry (CS) treatments in November 1994 and repeated in May 1996. Soil oxygen diffusion rate (ODR), fine root density (FRD), DBH, twig growth, leaf area and dieback were monitored for 4 years beginning in 1996. Both compaction treatments significantly reduced ODR at 15 cm. Early each season, ODR was below the 0.20 g/cm²/min threshold level reported to inhibit root growth in several species [Stolzy, L.H., Letey, J., 1964. Correlation of plant response to soil oxygen diffusion rates. Hilgardia 35, 567–576] for all treatments and depths. In summer each year, ODR was adequate in the shallow soils of all treatments, though often still significantly lower in compacted soils. At 30 cm, there were no consistent differences in ODR between compacted and uncompacted soil. Significant differences in FRD due to compaction treatments were inconsistent and limited to the upper 9 cm of soil in years 2 and 3. Reduced FRD in compacted soils may be a response to the reduced ODR in spring. There were no differences in DBH, twig growth, leaf area or dieback rating. Given the minimal difference in root growth, the lack of differences in top growth are understandable. This controlled study, and others preceding it, have failed to clearly show the underlying causes of tree decline and death commonly associated with soil compaction and addition of fill soil in real landscapes.     

Urban salt contamination impact on tree health and the prevalence of fungi agent in cities of the central Lithuania

An analysis of tree health in urban greeneries exposed to winter road salt contamination was carried out in the cities of Alytus and Kaunas, Lithuania, during spring and summer 2009–2014. Trees were assessed for crown dieback, crown defoliation and foliage discolouration. In addition, the prevalence of saprotrophic pathogenic fungi that cause sooty mold disease was assessed in street and recreational plantings. Tilia cordata Mill. (small-leaved lime) was found to be the most common tree species among urban deciduous trees. Summarising the tree foliage results, saprotrophic fungi were detected on 16 species plants belonging to 13 genera. Three species of fungal pathogens belonging to two genera, two families, two classes, and two divisions, and 12 species of anamorphic fungi from nine genera were isolated and identified from Tilia cordata leaves. The most frequent sooty mold disease agents were Aspergillus brasiliensis and Cladosporium herbarum. Nonetheless, a weak correlation between salt contamination and lime tree damage by sooty mold was found.     

大果杨梅新品种‘永冠’

‘永冠’是从‘东魁’杨梅中选育出的大果芽变新品种。果实近圆球形,平均单果质量为30.9g,最大可达53.0 g。果面红色或紫红色,果实柔软多汁,酸甜适中,可食率95.2%,可溶性固形物含量12.6%。在浙江黄岩果实6月下旬至7月初成熟,抗病性强,尤其抗杨梅枯枝病。     

Efficacy tests on commercial fungicides against ash dieback in vitro and by trunk injection

Ash dieback, caused by Hymenoscyphus pseudoalbidus Queloz et al. (anamorph Chalara fraxinea Kowalski), has emerged as a critical disease in urban areas and in the forests of many European countries. This study was conducted to evaluate six fungicides for their potential to control the disease. In vitro assays with different concentrations of the products against five different strains of the pathogen, illustrated that thiabendazole, propiconazole and allicin exhibited lower median lethal doses, procloraz completely killed half of the samples at higher concentrations, whereas copper sulphate and potassium phosphite were totally ineffective. Subsequently, the antifungal activities of the best three compounds were investigated in planta against H. pseudoalbidus by trunk injection. The rate of necroses development following artificial inoculation of 24 F. excelsior was significantly slowed down in the growing season by the treatment with thiabendazole and allicin. In the phenological phase and climatic conditions tested, and with the chosen formulation and injection method, propiconazole injections were impracticable. The results of this study, along with some technical suggestions for application in the field, support the idea of using organic and chemical endotherapic products to combat ash dieback symptoms in Fraxinus spp., with the safe and very low impact method of trunk injection.     

Urban London plane tree dieback linked to fungi in the Botryosphaeriaceae

Since the first report of the stain canker agent Ceratocystis platani in 2001 in Geneva, dieback of London plane trees (Platanus × acerifolia) has focused greater attention and an epidemiological monitoring has been implemented, as part of a compelling state directive for stain canker management. Genetic identification was carried out in order to ascertain the presence or absence of C. platani. We report here observations recorded between 2011 and 2013, of samplings from a total of 6 plane trees in 4 locations. Identification of bacteria and fungi was performed by sequencing of the rDNA ITS region for fungi, and of the 16S rRNA gene for bacteria. Fungi belonging to the Botryosphaeriaceae species occurred in almost every sampling, whereas Ceratocystis platani was only isolated in 2 trees. The 4 botryosphaeriaceous species, Diplodia mutila, Dothiorella sp., Diplodia seratia and Neofusicoccum parvum, could be responsible for the observed plane cankers, while other fungi could participate in the dieback symptoms. Since these species have been reported as canker agents on other tree species in Europe, artificial infections were carried out with pure cultures of Dothiorella sp., Diplodia mutila and Neofusicoccum parvum on young plane trees. Only Neofusicoccum parvum managed to provoke cork canker symptoms after a few months, but D. mutila and N. parvum were found in internal necrotic tissues. This is the first report of Dothiorella sp., Diplodia mutila and Neofusicoccum parvum associated with plane tree dieback in Switzerland and the first report of pathogenicity of Neofusicoccum parvum in plane trees. This survey showed that most cases of plane tree dieback in the Geneva region were not caused by C. platani and that other fungi could be responsible for similar symptoms.     

Sooty canker,a destructive disease of banyan (Ficus benghalensis L.) trees in landscapes of Kish Island (Iran)

Ficus benghalensis L (banyan tree) has been planted as ornamental tree in parks, landscapes as well as along roads and streets in many southern cities of Iran. During field surveys conducted in Kish Island (Hormozgān province) an unusual decline was noticed on F. benghalensis. Affected trees exhibited bark necrosis, peeled off bark and cankers on branches and aerial roots, yellowing and defoliation, branch dieback and eventually death. A black sooty mass of fungal spores under the bark as well as wood discoloration in cross sections were also observed on infected parts of trees and pruning wood debris. Samples were collected from all affected parts of trees showing disease symptoms, pruning wood debris as well as rove arthropods in close proximity to the trees for the presence of fungal inoculum. In this study 239 Botryosphaeriaceae-like isolates were obtained from discoloured wood tissues, pruning wood debris and from the bodies of collected arthropods. Based on morphological characteristics and DNA sequence data of ITS and tef-1α gene regions, isolates were identified as Lasiodiplodia theobromae and Neoscytalidium dimidiatum. Pathogenicity of both species was performed on the branches of banyan trees and L. theobromae was more virulent, based on the length of necrotic lesions in the wood, than those of N. dimidiatum. This study is the first report of N. dimidiatum associated with sooty canker and dieback of F. benghalensis worldwide. Our study showed for the first time that L. theobromae and N. dimidiatum can also be associated with some arthropods. Our outcomes can improve the management strategies of trunk diseases caused by Botryosphaeriaceae species on ornamental trees in landscapes.     

桃花芽生理分化与枝梢类型、芽在枝梢上所处部位的关系研究

采取喷施赤霉素(GA_3)的方法对红翼(Redwing)、阳冠(Suncrest)和红皮(Redskin)等3个桃品种的花芽生理分化期的研究表明:不同类型的枝梢,不同部位的芽,进入花芽生理分化期以及持续时间存在显著差异。花芽分化盛期的长短虽取决于品种自身的结果习性,但在长梢生长显著地减缓之前1—2周其长度约占最终生长总长度的70—80％时,所有供试品种均处于生理分化盛期。     

Cane Morphology and Anatomy Influence Freezing Tolerance in Vitis vinifera Cabernet franc

In 2014 and 2015, Ohio vineyards were exposed to multiple freeze events of –20 °C or lower, resulting in vine dieback, i.e., complete damage of above ground parts in Vitis vinifera. Grapevines that sustained dieback were rehabilitated for trunk replacement by training 1-year-old shoots with two distinct morphologies, based on internode diameter of large (L) and normal (N). This study evaluated the impact of cane morphology (L and N) in V. vinifera Cabernet franc on freezing tolerance (FT) of bud, phloem, and xylem tissues in relation to their respective anatomical structures and carbohydrate concentrations. Compared to N canes (7–9-mm diameter), L canes (10–15 mm) in Cabernet franc were considered vigorous and had the following morphological characteristics: long and heavy, with long and wide internode, and presence of numerous laterals. Furthermore, cane anatomy was also different with L canes having a significantly higher number of vascular transport units, xylem vessels, and phloem fibers than those in N canes. Freezing tolerance of buds and phloem was also different between the two cane types, with L canes being more cold sensitive than N canes, especially during fall acclimation and late-winter deacclimation. Sugar concentrations, however, were not different between L and N canes. These results suggest that cane morphology and anatomy play a significant role in affecting FT and the large and abundant anatomical structures of phloem and xylem contributed to the reduced FT of these tissues. In all practicality, this study suggests the best cultural practice for trunk replacement, and vine recovery should include the removal of the undesirable vigorous and cold sensitive canes during pruning.     

Analysis of factors governing water flow traits in fruiting plants twigs

We compared hydraulic traits of 18 tropical/subtropical fruit-producing species plants and a further 18 from temperate zone. Plants were classified into four categories by height: tall tree (>10 m), small tree (4–9 m), shrub (1–4 m) and vine. We measured ratios [(cross-section area of xylem)/(cross-section area of twig)], and the diameters and numbers of xylem vessels in microscopic images. We calculated the water flow index (WFI: Σr⁴ S⁻¹ × xylem ratio, where, r is the vessel radius, and S is the xylem cross-section area) according to Hagen–Poiseuille's law. Vine had thick vessels and remarkably higher WFI than free-standing trees in both temperate and tropical fruit species. Vessel diameter increased as trees being taller in both in latitudinal groups. Xylem vessel number decreased with height in temperate fruit trees but not in tropical species. WFI increased with tree height of both latitudinal groups. There were no significant effects of latitude on WFI.     

Testing the suitability for coastal green areas of three ornamental shrub species through physiological responses to the saline nebulization

Besides abiotic constraints, plants along the coastal urban areas must face additional cues such as saline aerosol, which impact net plant CO₂ assimilation (P_n), reducing biomass and influencing their aesthetic features. In this study, three species (Photinia × fraseri, P; Escallonia rubra, E; and Feijoa sellowiana, F) were subjected to saline nebulization (SN) with a 100 mM NaCl solution. Analyses were performed at 0, 10, and 20 days by monitoring the ion accumulation in plant organs, leaf osmotic potentials, gas exchange, chlorophyll a fluorescence parameters, and chlorophyll contents. Overall, E-SN plants absorbed more Na⁺ and Cl⁻ in leaves than P-SN and F-SN ones. This phenomenon was influenced by leaf ‘wettability’ features such as the contact angle of water droplets, droplet retention, and water storage capacity, and the effectiveness of translocating these ions on twig tissues. SN increased the leaf osmotic potential (regardless of species). At 10 days (i.e., moderate stress conditions), P_n declined in all SN species, but more severely (−82 %) in E-SN plants. The observed P_n reductions were due to different limiting factors according to the plant species: P_n was reduced by non-stomatal limitations in P-SN plants, stomatal closure in F-SN, and a combination of both in E-SN individuals. At 20 days (i.e., severe stress conditions), in all SN-plants, lower values in all the physiological parameters than controls were observed, indicating a low tolerance to prolonged SN. The work shows that non-destructive physiological measurements provide a reliable assessment of plant tolerance to SN, which can help growers to select ornamental species suitable for coastal green areas.     

Top working method and bloom density of pollinizers as productive determinant for spur type apple (Malus x domestica Borkh.) cultivars

Apple (Malus x domestica Borkh.) shows gametophytic self incompatibility and requires cross pollination by suitable pollinizers. Gradual decline in natural pollinators and insufficient proportion of pollinizers have been observed in the apple orchards over the years across the North Western Himalayan region. This situation resulted in considerable pollination problem in the region. The present study was undertaken (during the years 2006–2010) to examine the effect of top working methods and time as well as type of pollinizers on different growth parameters for efficient pollination management. Chip budding performed in fall, late winter and summer gave significantly higher success rate (90.0, 89.8 and 80.9%, respectively). Other methods viz., side rind graft (85.6%) and cleft graft (71.2%) during February–March, and T-bud (71.7%) during July–August also gave better success. The highest shoot numbers (4.1) and length (92.8 cm) were recorded when chip budding was performed during September–October and February–March, respectively. In 4th year, chip budded scion branches of all the pollinizers recorded significantly higher number of spurs/m twig length with a range of 22.8 (December–January) to 24.7 (September–October). Significantly the highest bloom density (22.1) was recorded on chip budded (February–March) branches of pollinizers in 4th year. Fruit set on top worked trees of ‘Oregon Spur’ was only in the range of 18.0–20.1% in 1st year and reached to the range of 35.6–41.5% in 4th year. Seed numbers/fruit also increased to the range of 7.3–7.9 in 4th year from 2.9 to 4.6 in 1st year. All these factors resulted in better yield efficiency (2.6–3.8) of ‘Oregon Spur’ in 4th year. ‘Manchurian’ crab produced significantly higher shoot length of 86.5–87.2 cm and 146.1–149.2 cm in 1st and 4th years, respectively. However, ‘Stark Spur’ produced the highest number of spurs/m twig length of 28.9 when grafted/chip budded during December–January or February–March, and 27.1 when chip/T-budded during September–October or July–August. Top working with ‘Manchurian’ crab also resulted in significantly higher fruit set (44.2–45.4%) and yield efficiency (3.6–3.8) on ‘Oregon Spur’ in 4th year. This was followed by ‘Stark Spur’ as pollinizer (37.1–38.2% and 2.9–3.1, respectively). Highly significant positive correlation of shoot numbers, spur density and bloom density of pollinizers with fruit set and yield efficiency of ‘Oregon Spur’ were observed. ‘Manchurian’ crab was found to be very efficient as pollinizer, followed by ‘Stark Spur’ for spur type ‘Oregon Spur’ apple cultivar on the basis of higher bloom density and fruit set parameters.     

Reponses of mamey sapote (Pouteria sapota) trees to continuous and cyclical flooding in calcareous soil

Physiological and growth responses of ‘Pantin’ and ‘Magana’ mamey sapote (Pouteria sapota) trees to continuous and cyclical flooding were studied in a series of experiments. Trees were grown in containers in a very gravelly loam soil and were subjected to continuous flooding of the root zone for 30–66 days (Experiments 1 and 2) or alternating flooding–unflooding cycles for 50 days (Experiments 3–5). For all experiments, the control treatment consisted of nonflooded trees. Net CO₂ assimilation (A) and stomatal conductance (g_s) decreased within 3 days of continuous flooding and internal CO₂ concentration was significantly higher in leaves of flooded than nonflooded plants. In the cyclic flooding experiments, trees were flooded in 3- to 6-day cycles and then unflooded for the same time periods. Stomatal conductance and A decreased within 3 days of flooding, leaf epinasty occurred between days 5 and 10, leaf senescence and abscission occurred between days 15 and 30, and branch dieback and tree death occurred between days 30 and 60. Three cycles of 3-day flooding and 3-day recovery of trees had little effect on leaf gas exchange of ‘Magaña’ trees. Similarly, ‘Pantin’ trees survived 3 cycles of 6 days of flooding interspersed with 3–6 days of recovery despite consistent decreases in g_s and A during flooding. Stomatal conductance and A of both mamey sapote cultivars decreased within a few days of flooding and this species appears to have intermediate flooding tolerance compared with other tropical fruit crops based on tree survival.     

光肩星天牛的生活习性及防治

光肩星天牛是园林树木的重要蛀干害虫,分布于国内二十多个省市,它不仅造成树势衰弱,枝条枯死,而且被害的枝干易被大风折断,严重者往往引起全株死亡。危害相当严重。是一种毁灭性蛀干害虫,树木从干基直到侧枝、顶枝都可受害,受害严重的树木千疮百孔将死亡或被砍伐。     

Landscape-scale assessment of tree crown dieback following extreme drought and heat in a Mediterranean eucalypt forest ecosystem

Mediterranean regions are under increasing pressure from global climate changes. Many have experienced more frequent extreme weather events such as droughts and heatwaves, which have severe implications for the persistence of forest ecosystems. This study reports on a landscape-scale assessment investigating potential associated factors of crown dieback in dominant tree species following an extreme dry and hot year/summer of 2010/11 in the Northern Jarrah Forest of Western Australia. Analyses focussed on the influence of (i) geology, (ii) topography, (iii) climate, and (iv) fire history. The results showed that trees on specific soils were more likely to show canopy dieback. Generally, trees on rocky soils with low water holding capacity were found to be affected more frequently. Other explanatory factors identified that dieback occurred (i) on sites that were close to rock outcrops, (ii) in areas that received a slightly higher amount of annual rainfall compared to the surrounding landscape, (iii) on sites at high elevations and (vi) on steep slopes, and (v) in areas that were generally slightly warmer than their surroundings. These results expand our understanding of how landscape-scale factors contribute to the effects of an extreme drought and heating event in Mediterranean forest ecosystems, and give indications of where changes are likely to occur within the landscape in the future. The analogues with other Mediterranean climate regions make the results of this study transferable and a starting point for further investigations.     

Ultrastructural observationof lemon fruit abscission

Ultrastructural changes in the abscission zone between ovary wall and floral disc were followed during abscission of young lemon (Citrus limon (L.) Burm. f. cultivar ‘Villafranca’) fruit explants. Although some cell breakage was observed by light and scanning electron microscopy as well as cell wall dissolution, only middle lamella dissolution was observed by transmission electron microscopy, strongly suggesting that pectic substance dissolution is the primary cause of cell separation.Prior to cell separation the middle lamella of the cell wall stained deeply, the amount of rough endoplasmic reticulum (ER) profiles increased, and the number of Golgi bodies also increased. However no change in mitochondria or chloroplast structure was observed before cell separations, and no microbodies were observed.In Ethephon (2-chloroethylphosphonic acid)-treated explants, essentially similar cytoplasmic and cell wall changes occurred during the course of abscission, but the changes were more rapid.     

东北寒地96份李种质资源表型性状遗传多样性分析

为了深入了解李（Prunus L.）种质资源表型性状的变异特点和多样性,按照《李种质资源描述规范和数据标准》,对黑龙江省农业科学院牡丹江分院李资源圃内保存的96份寒地李种质资源20个描述型表型性状进行观测和描述,对16个数量型表型性状进行相关性、聚类、主成分等分析。结果表明,20个描述型性状,共观测到66个变异类型,其中叶片形状、果皮颜色、果核形状等变异范围较大。Shannon-Wiener信息指数（H）和Simpson遗传多样性指数（D）变化范围分别为0.3768 ~ 1.3993和0.2188 ~ 0.7196,其中果皮颜色（H：1.2093,D：0.6814）、叶片形状（H：1.1227,D：0.5484）等性状多样性指数较高。16个数量型性状中,单果质量变异系数最大,为61.32%;果形指数变异系数最小,为8.72%。聚类分析将96份寒地李种质资源在欧式距离22处将各种质资源分为3大类群,其中第Ⅰ类可用于选育离核、抗性强的品种;第Ⅱ类可用于选育抗性强、丰产品种;第Ⅲ类可用于选育果大、可食率高、离核品种。主成分分析结果表明,前5个主成分累计贡献率达到78.191%,主要有果实纵径、果实横径、1年生枝粗等性状,主要反映了果实大小和枝条性状因子,果实性状对于东北寒地李种质资源表型性状变异的贡献率最大,一年生枝条次之。结合相关性分析结果,16个数量型性状可简化为果实纵径、果实横径、叶片宽、果核横径、果形指数、叶片长、1年生枝粗7个主要指标,提高了寒地李种质资源评价和选育鉴定工作的效率。性     

Risk of root intrusion by tree and shrub species into sewer pipes in Swedish urban areas

Blockages in sewer pipes caused by roots are very common and several tree and shrub species are reported to be particularly likely to cause root intrusion. This study examined the relative ability of roots of different species to intrude into urban sewer pipes.Data on root-intruded pipes and the woody plants surrounding these pipes were collected from two Swedish cities, Malmö and Skövde. Plant material, location data and closed-circuit television (CCTV) inspections on root-intruded pipes with a total length of 33.7 km, containing 2180 different points of root intrusion, were examined. An inventory of 4107 woody plants was compiled.The results showed that broad-leaved trees dominated as a cause of root intrusion, but that conifers and a number of shrubs, e.g. the genera Ligustrum, Spiraea and Syringa, were also likely to have caused root intrusion. Malus floribunda Van Houtte was found to have the highest mean share of root intrusions per estimated number of pipe joints when all joints and all root intrusions within a 10 m radius from trees were calculated (0.694, maximum number of intrusions per joint 1.0), while Populus canadensis ‘Robusta’ Moench had the second highest, with 0.456 intrusions per estimated joint. However, other Malus and Populus species and cultivars had a much lower mean share of root intrusions.Most species seemed capable of causing root intrusion, and not only species of the genera Populus and Salix that were previously seen as the species most likely to cause damage to stormwater and sewer systems. There were differences in the frequency of joint intrusion by roots of different species, but the reasons for these differences were not identified and further research in the area is needed.     

‘梨红叶枯萎病’防治研究

‘梨红叶枯萎病’是湖北省一些碱性沙土梨园近年来出现的一种病害,受害梨树整株死亡,成片毁园,经研究证明此系缺硼引起。但梨树的需硼范围甚小,适宜的土壤速效硼含量指标大致为0.14～0.55×10~(-6),梨叶含硼指标,约为21～47×10~(-5)。施用不当,常会引起硼毒为害。     

金秋梨叶、梢和果实的生长动态及相关性

金秋梨自展叶到叶面积几乎停止扩大所需时间需24d,前12d叶片生长速度快,叶面积迅速增大;12d以后,叶片扩展缓慢,叶面积增加速率慢;24d后,叶片几乎停止生长。新梢的加长生长和加粗生长均可分为3个时期,持续时间与新梢种类有关。金秋梨果实的生长速率有3个高峰,分别在花后40d、82d和131d。