首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Since 1984 when a new Ministerial Regulation on fire blight came into force, there have been 20 protected regions in the Netherlands, where nurseries of rosaceous plants, and pear and apple orchards are extra protected against fire blight. This policy is also necessary to meet the requirements of the European Community (EC) on fire blight. Two of the measures in the protected regions are the prohibition of flowering of the native hawthorn (Crataegus monogyna andC. laevigata), and destruction of blighted plants. In the unprotected regions, flowering is allowed, and destruction of blighted plants is limited to a zone of 500 metres around orchards.For three years, the effectiveness of preventing flowering of hawthorn in protecting pear orchards against fire blight infection was studied in the field. Five test areas of about 3 km × 3 km were chosen with hawthorns and pear orchards. Two of these areas were in protected regions and three in unprotected regions. The more than 50 000 hawthorns in the areas were grouped into 1125 sites of hawthorn. The 126 orchards larger than 0.2 ha contained about 180 000 trees.During the three years light to moderate epidemics of fire blight were observed in the regions. Fire blight occurred in 2.3% of the non-flowering sites and 19.8% of the flowering (or fruiting) sites at least once in 1987, 1988 or 1989. The prohibition of flowering for hawthorn in protected areas was rather well implemented, so that in protected areas a smaller proportion of sites of hawthorns had fire blight (4.1%) than in unprotected areas (14%). Moreover, there were fewer sites per square kilometre in the protected areas (13) than in the unprotected areas (26).In protected areas, 53% and in unprotected areas 59% of the pear orchards had fire blight during 1987, 1988 or 1989. The difference was not significant. The first reason for the ineffectiveness of the preventing of flowering prevention in hawthorn to control fire blight in pear orchards was the inadequate hygiene of the pear orchards in both types of region. If it be assumed that a new focus is most probably initiated by the nearest existing focus, the second reason was that fire blight hardly spread from hawthorn to pear in the period of this study. Spread of fire blight within pear orchards and between pear orchards occurred frequently.  相似文献   

2.
Following failure in control of fire blight with streptomycin, the distribution of streptomycin-resistant strains ofErwinia amylovora in Israel was surveyed. During 1994–1997 109 pear, apple, loquat and quince orchards were monitored. Streptomycin-resistant strains ofE. amylovora were recovered from flowers and from infected branches collected at 18 locations in the Sharon, Galilee and Golan Heights regions. In the Sharon region all the isolated strains ofE. amylovora were streptomycin-resistant, whereas in the Galilee and Golan Heights, resistant as well as sensitiveE. amylovora strains were recovered at different locations. In the southern coastal plain no resistance could be detected. Streptomycin-resistant strains ofE. amylovora did not hybridize with the DNA probe SMP3, and resistance could not be transferred by mating to a sensitive strain, suggesting that streptomycin resistance in Israel is not plasmid-mediated. Fire blight symptoms were observed, for the first time, on pear blossoms during the autumn of 1994. A high population of 2x 106-6x 107 CFU/flower in the autumn of 1995 and of 1996 was correlated with the appearance of blossom blight symptoms.  相似文献   

3.
ABSTRACT The possibility of using local and imported warning systems for the management of fire blight (caused by the bacterium Erwinia amylovora) in pears was tested in Israel from 1997 to 2000. Three imported systems (MARYBLYT 4.3, BIS95, and Cougarblight 98C) and one local system (Fire Blight Control Advisory [FBCA]) were used. All systems were tested in simulation experiments; MARYBLYT 4.3 and FBCA were also tested in orchard experiments under natural infections. Simulation experiments included 193 orchard-plots in which the time of disease onset enabled us to determine the date of infection. Thirty-five experiments were conducted in commercial orchards; in 10 of these, fire blight developed naturally. The performance of the imported warning systems was too variable to be accurately used under Israeli conditions. In the simulation experiments, the success rate (i.e., the capacity of the systems to predict the exact date of the occurrence of infection episodes) of the imported systems was low (3 to 55%) with considerably large variability among years (CV = 30 to 67%). Similar results were obtained in the orchard experiments for MARYBLYT 4.3: in only two of five experiments where plots were managed according to that system was disease severity significantly lower than that recorded in untreated control plots. In comparison, the local system, FBCA, predicted most infection episodes in the simulation experiments with low variability (99%, CV = 1.0%). In the orchard experiments, adequate disease suppression was achieved in all eight experiments in which FBCA recommendations were followed. We concluded that it was not possible to import and successfully implement fire blight warning systems in Israel that have been developed in regions with dissimilar environmental conditions.  相似文献   

4.
Oxolinic acid (OA) has been the only bactericide used against fire blight in pear and quince orchards in Israel since 1998. OA-resistant Erwinia amylovora strains (Ea-OAR) were detected in several orchards in two restricted areas in the northern Galilee region during 1999–2001. In the following years, resistant strains could not be detected in some of these locations. Documenting the fate of Ea-OAR strains in commercial orchards at eight sites in northern Israel during 2000/03 revealed that the resistant population appeared irrespective of the number of sprays applied and the severity of the disease. The persistence of the Ea-OAR populations varied from site to site, ranging from 4 to 20 months; these differences could be attributed to the fire blight management activities of growers. Comparative studies on the fitness of Ea-OAR and E. amylovora strains sensitive to OA (Ea-OAS) were conducted in vitro and in planta using two strains of each group. In four of the six comparisons, disease incidence on detached blossoms inoculated with Ea-OAS was significantly higher than that on blossoms inoculated with Ea-OAR. In two experiments conducted on 8-year-old pear trees grown under netting, the colonization of Ea-OAS in blossoms, annual shoots and perennial spurs was significantly higher than that of the Ea-OAR. In two experiments conducted on 2-year-old trees grown under netting in an experimental station, the incidence of shoots exhibiting fire blight symptoms and the rate of symptom progress within the branches were significantly higher in trees inoculated with Ea-OAS than in those inoculated with Ea-OAR. The results of this study suggest that OA-resistant E. amylovora strains have lower fitness than wild-type strains. These findings may have implications for fire blight management.  相似文献   

5.
Fire blight, caused by Erwinia amylovora, is a major disease threat to apple, pear and other pome fruit worldwide. The disease is widespread in Europe and has recently become established in Switzerland. Antibiotics are the most effective controls used in North America but these are not permitted for agricultural use in most European countries. A newly registered biological control product Biopro®, based on the antagonist Bacillus subtilis strain BD170, is being used as an alternative strategy for fire blight management. A specific molecular marker was developed for monitoring the spread of this agent on blossoms after Biopro® spray application in a Swiss apple orchard throughout the bloom period for 2years. Direct spraying resulted in efficient primary colonisation of pistils in flowers that were open at the time of treatment. Subsequent bacterial dissemination (secondary colonisation) of flowers that were closed or at bud stage at the time of treatment was observed but was found to be dependent on the timing of treatments relative to bloom stage in the orchard. Foraging honeybees were shown to be disseminators of Biopro®. We also report detection of the biocontrol agent in honey collected from hives where bees were exposed by placing Biopro® at the entrance or in the hatching nest and from hives that were simply placed in sprayed orchards.  相似文献   

6.
梨火疫病由梨火疫病菌（Erwinia amylovora）引起,可以通过蜜蜂授粉传播而加重危害。为做好香梨安全授粉工作,防止因直接放蜂造成梨火疫病的大流行,本研究测试了香梨花上分离的一株解淀粉芽孢杆菌（Bacillus amyloliquefaciens）对梨火疫病菌的拮抗效果,并利用自行研发的“蜜蜂导向盒”进行了蜜蜂传播生防菌防病试验。结果表明“蜜蜂导向盒+生防菌”技术在香梨花期可以有效控制由梨火疫菌引起的花腐和枝枯。  相似文献   

7.
Brown spot disease on pear caused by Stemphylium vesicarium may affect leaves and fruits. Inoculum sources present on orchard floors play an important role in the epidemiology of pear brown spot. The pathogen can overwinter on plant residues and multiply and spread on the residues during the growing season. In the Netherlands, brown spot characteristically occurs only in a fraction of the orchards per season. Until now, no tools are available for Dutch pear growers to predict the risk of brown spot in specific orchards. As a consequence, preventive fungicide sprayings are common. The concentration of DNA of pear-pathogenic S. vesicarium was quantified by a specific TaqMan-PCR assay for various types of plant residues present on orchard floors to evaluate their importance as potential inoculum source. The pathogen was often found in residues of pear leaves, grasses and weeds, but only occasionally in mummies and prunings. Studies of the population dynamics showed that S. vesicarium decreased in dead pear leaves during early winter whereas pathogen populations developed with irregular pattern during the growing season on residues of weeds and grasses. Based on DNA concentrations of S. vesicarium in plant residue samples taken in 78 to 106 orchards in the springs of 2010, 2011 and 2012, the risk of brown spot development could be predicted for individual orchards. Such a risk prediction will allow growers to adapt their fungicide spray schedules to avoid unnecessary sprays in low-risk orchards.  相似文献   

8.
Post‐harvest diseases of apple and pear cause significant losses. Neofabraea spp. and Cadophora spp. infect fruits during the growing season and remain quiescent until disease symptoms occur after several months in storage. Epidemiological knowledge of these diseases is limited. TaqMan PCR assays were developed for quantification of N. alba, N. perennans, C. malorum and C. luteo‐olivacea in environmental samples. Various host tissues, dead weeds and grasses, soil and applied composts were collected in 10 apple and 10 pear orchards in May 2012. Neofabraea alba was detected in 73% of samples from apple orchards and 48% from pear orchards. Neofabraea perennans was present in a few samples. Cadophora luteo‐olivacea was detected in 99% of samples from apple orchards and 93% from pear orchards, whilst C. malorum was not detected in any sample. In apple orchards, highest concentrations of N. alba were found in apple leaf litter, cankers and mummies, and of C. luteo‐olivacea in apple leaf litter, mummies and dead weeds. In pear orchards, N. alba and C. luteo‐olivacea were found in highest concentrations in pear leaf litter and in dead weeds. Substrate colonization varied considerably between orchards. The temporal dynamics of pathogens was followed in four apple orchards and four pear orchards. In apple orchards the colonization by pathogens decreased from April until August and increased from September until December. This pattern was less pronounced in pear. Knowledge on population dynamics is essential for the development of preventative measures to reduce risks of fruit infections during the growing season.  相似文献   

9.
Control of the codling moth,Cydia pomonella (L.) (Lepidoptera: Tortricidae), by pheromone-mediated mating disruption, was studied in Israel using two types of dispensers: Shin-Etsu twist-tie (normal and long-life) and TNO matrix formulation (square wafers). Factors affecting mating disruption: initial pest population density, timing of the pheromone application, early season insecticide treatments and monitoring of the pest, were evaluated. Efficacy of mating disruption was assessed by comparing catch of males in pheromone traps located in pheromone-treated and chemically sprayed control plots. Fruit infestation during the season and at picking time was the major criterion to assess mating disruption. The preferred time for pheromone application was before the first flight of the moth. When pheromones were applied at a later stage, one or two early insecticide sprays had to be used to reduce the initial level of the codling moth population. In all tests, trap catch in pheromone-treated plots was drastically reduced as compared with respective control plots. In pheromone-treated plots where total seasonal trap catch (after pheromone application) was less than 12 males/trap, fruit infestation was less than 1.5%; zero trap catch resulted in 0.1-0.3% infestation. At high population levels, mating disruption was ineffective, with the rate of infestation at picking-time being similar in pheromone-treated and control plots. All the field tests indicated that mating disruption with either Shin-Etsu ropes or TNO squares can control codling moth infestations in apple and pear orchards, at relatively low densities of the pest, as efficiently as commercial insecticide sprays.  相似文献   

10.
Brown spot of pear (Pyrus communis) caused by Stemphylium vesicarium is an important disease in fruit‐growing areas of Europe. The control of brown spot is based on protectant sprays of fungicide applied, at 7‐ to 15‐day intervals depending on the type of fungicide, from fruit set to preharvest regardless of the risk of infection. A forecasting model has been developed and can be used for timing the fungicide applications and to eliminate unnecessary sprays. The model quantifies the relationship between wetness duration and temperature in disease severity and can be used as a tool for the prediction of disease infection periods. The capacity of risk prediction was validated over 2 years. The fungicide sprays scheduled by the STREP forecaster were evaluated in commercial orchards during 3 years in different climatic areas in Spain and Italy. The results showed consistently that use of the STREP model minimized the number of fungicide sprays compared with a protectant schedule, but without decreasing the quality of commercial disease control. The susceptibility of selected European pear cultivars to infection by S. vesicarium and the influence of fruit age were also determined. The implementation of the model in warning stations will require the combination of predictions by the STREP model, the level of inoculum and the sensitivity of phenological stage and pear cultivar.  相似文献   

11.
A collection of 205 strains ofErwinia amylovora isolated in Israel over a period of 12 years has been established. The strains were isolated from different varieties of pear, apple, loquat and quince grown in Israel, and collected from different locations in the country. They were characterized in respect to degree of virulence on several hosts and serological and molecular characters. Pathogenicity tests carried out on flowering branches of pear and apple, shoots of pears, and on trees of pear and loquat grown in containers outdoors, revealed no significant differences in the severity of blossom blight or shoot blight among the various strains. ELISA and immunofluorescence assays revealed no serotypic groups among the Israeli strains. Genomic diversity was studied by random amplified polymorphic DNA (RAPD) analysis using 24 arbitrary 10-base primers. All the strains examined (45 Israeli and 11 from Egypt, Cyprus and Greece) produced the same RAPD patterns with each of the primers used. Amplification patterns were indistinguishable from those produced by strains isolated from the neighboring countries. Results presented in this study suggest that the population ofE. amylovora in Israel is homogenous.  相似文献   

12.
The efficacy of oxolinic acid (at 200 and 300 μg a.i./l) and of several antibiotic compounds (streptomycin sulfate at 100 μg a.i./l, glycocide B at 700 μg a.i./l, kasugamycin at 80 μg a.i./l and gentamicin sulfate at 30 and 60 μg a.i./l) againstErwinia amylovora, the causal agent of fire blight in pears, was evaluated in 43 orchard experiments in 1997–2000 in Israel. In addition to the above orchard experiments, the efficacy of the bactericides was tested in live experiments with artificial inoculation. Natural fire blight symptoms were observed in 16 of the 43 experiments; in 13 of them, disease intensity and its distribution among the experimental plots provided a basis for data analysis, leading to reliable conclusions concerning the efficacy of the tested bactericides. Oxolinic acid at 300 μg a.i./l was highly effective againstE. amylovora and reduced disease severity significantly in all experiments, as compared with the untreated plots; however, a concentration of 200 μg a.i./l was not effective in some cases. Among the tested antibiotics, only gentamicin sulfate was as effective as oxolinic acid. Results of the artificial inoculation experiments corroborated those obtained in the naturally infected orchards. The pre-infection activity of oxolinic acid was determined on blossom clusters that were sprayed with the bactericide before inoculation. Control efficacy on blossom clusters sprayed 1–4 days before inoculation ranged from 68% to 80%, a level which did not differ significantly from that observed on blossom clusters sprayed on the day of inoculation (80% control). The postinfection activity of oxolinic acid was determined on blossom clusters that were sprayed with the compound after inoculation. Oxolinic acid was as effective when applied 1 or 2 days after inoculation as when it was applied on the day of inoculation; however, application of the bactericide 3 days after inoculation no longer resulted in significant disease suppression. Oxolinic acid has been used commercially in Israel since 1998 with appreciable success. Contribution No. 533-00 from the Agricultural Research Organization  相似文献   

13.
ABSTRACT Fire blight, caused by Erwinia amylovora, is the most serious bacterial disease of pear and apple trees. Biological control with strains of Pantoea agglomerans (syn. Erwinia herbicola) may provide an effective disease management strategy for fire blight. Most strains of P. agglomerans evaluated for suppression of fire blight produce compounds that inhibit the growth of E. amylovora in culture. The role of these inhibitory compounds in fire blight suppression in orchard environments has not been studied. In seven field trials in Oregon, we compared the population dynamics and disease suppression with P. agglomerans Eh252, a strain that produces a single antibiotic, with its near-isogenic antibiotic-deficient derivative, strain 10:12. Water or suspensions of Eh252 or 10:12 (1 x 10(8) CFU/ml) were applied at 30 and 70% bloom to pear or apple trees. Aqueous suspensions of freeze-dried cells of E. amylovora (3 x 10(5) CFU/ml) were applied at full bloom. Additional trees were treated with streptomycin or oxytetracycline at 30 and 70% bloom and in some experiments, 1 day after application of the pathogen. Population sizes of Eh252 or 10:12 on pear blossoms were estimated by spreading dilutions of blossom washes on culture media. Average population sizes of Eh252 and 10:12 on blossoms ranged from 10(5) to 10(7) CFU, and in five of six trials, the relative area under the population curve of Eh252 was not significantly different than that of its derivative 10:12. Both Eh252 and 10:12 reduced the growth of the pathogen on blossoms compared with inoculated water-treated controls. Eh252 significantly decreased the incidence of fire blight in six of seven field trials compared with the incidence on water-treated trees, and 10:12 similarly reduced the incidence of fire blight in four of seven trials. In three of seven field trials, trees treated with Eh252 had a significantly lower incidence of fire blight compared with trees treated 3 with 10:12. Overall,3 Eh252 reduced the incidence of fire blight by 55 +/- 8%, 10:12 by 30 +/- 6%, streptomycin by 75 +/- 4%, and oxytetracycline by 16 +/- 14%. The effectiveness of strain 10:12 compared with water treatment indicates that other mechanisms (e.g., competitive exclusion or habitat modification) also contribute to disease suppression by P. agglomerans. The increased suppression of fire blight by the parental strain Eh252 compared with the antibiotic-deficient mutant 10:12 indicates that antibiosis is an important mechanism of biological control of fire blight.  相似文献   

14.
During the 1960s, the California pear industry, on a per acre basis, was among the heaviest users of pesticides. Each season, multiple sprays of up to 14 active ingredients (chlorinated hydrocarbons, organophosphates and carbamates) were typically applied for control of insects and mites. The cost of control escalated while damage from arthropod pests increased owing to greater pest resistance and more pest resurgence. The pear industry suffered classic symptoms of the ‘pesticide treadmill’. By the late 1960s, key pear industry leaders demanded action. Simultaneously, newly emerging concepts of IPM were being developed and funded. With public awareness and environmental activism on the rise in the wake of Rachel Carson's Silent Spring, the stage was set for change. This paper elucidates how pear growers, university researchers and extension agents, environmentalists, government regulators, private consultants, farm chemical suppliers and others contributed to the reduction in insecticide use in California pear orchards. Today, arthropod IPM in pears is characterized as relatively low input, biologically intensive and very successful. For example, in 2008 many pear growers only applied between three and five active ingredients (mainly organically certified) per season for control of arthropods. Copyright © 2009 Society of Chemical Industry  相似文献   

15.
Treatments with prohexadione-calcium led to lowered incidence of fire blight, scab and other diseases in pome fruit trees and other crop plants. In addition to acting as a growth regulator, prohexadione-calcium interferes with flavonoid metabolism and induces the accumulation of the 3-deoxycatechin luteoliflavan in shoots of pome fruit trees. Luteoliflavan does not possess any remarkable antimicrobial activity. Therefore luteoforol, its unstable and highly reactive precursor, has been tested in vitro for its bactericidal and fungicidal activities. Luteoforol was found to be highly active against different strains of Erwinia amylovora, the causal agent of fire blight, and all other bacterial and fungal organisms tested. Phytotoxic effects were also observed in pear plantlets. The results obtained indicate that prohexadione-calcium induces luteoforol as an active principle with non-specific biocidal properties. It is proposed that luteoforol is released upon pathogen attack from its cellular compartment and inhibits further disease development by destroying pathogen cells as well as by inducing a hypersensitive-like reaction in the host plant tissue. This mechanism would be closely analogous to the one known for structurally related phytoalexins in sorghum.  相似文献   

16.
Pear blossoms are the plant tissue that is most vulnerable to infection byErwinia amylovora (Burrill) Winslowet al., the causal agent of fire blight. The interacting effects of temperature, wetness duration and inoculum size on the development of fire blight symptoms in detached pear blossoms were determined in three sets of experiments conducted under controlled conditions. It was expected that this information would facilitate the improvement of a warning system used in fire blight management. Results of the ANOVA tests of the data revealed highly significant interactions among the factors tested. The factors that contributed most to disease incidence were temperature and inoculum size; effects of wetness duration were significant in some cases, but that effect was small. It was further demonstrated that the effects of the interaction of these factors on the incidence of blossom infection may be understood in terms of the general concept of compensation. According to this concept, conditions highly favorable for one of the factors essential for pathogen development may compensate for other factors, for which the conditions are less favorable. As a result of the complex interactions observed between the biotic and abiotic factors, because of compensation relationships and because some of the factors cannot be estimated adequately (for example, inoculum level), it was concluded that it is not yet possible to improve fire blight management by using data on the quantitative relationships between biotic and abiotic factors. Contribution No. 532/02 from the Agricultural Research Organization. http://www.phytoparasitica.org posting Feb. 20, 2003.  相似文献   

17.
Stemphylium vesicarium (teleomorph: Pleospora herbarum) is the causal agent of brown spot disease in pear. The species is also able to cause disease in asparagus, onion and other crops. Saprophytic growth of the fungus on plant debris is common. The objective of this study was to investigate whether isolates of S. vesicarium from different hosts can be pathogenic to pear. More than hundred isolates of Stemphylium spp. were obtained from infected pear fruits, dead pear leaves, dead grass leaves present in pear orchard lawns as well as from necrotic leaf parts of asparagus and onion. Only isolates originating from pear orchards, including isolates from dead grass leaves, were pathogenic on pear leaves or fruits in bioassays. Non-pathogenic isolates were also present in pear orchards. Stemphylium vesicarium from asparagus or onion, with one exception, were not pathogenic to pear. Analysis of the genetic variation between isolates using Amplified Fragment Length Polymorphism (AFLP) showed significant concordance with host plants. Isolates from asparagus or onion belonged to clusters separate from the cluster with isolates from pear or grass leaves collected in pear orchards. Multilocus sequencing of a subset of isolates showed that such isolates were similar to S. vesicarium.  相似文献   

18.
黄伟  盛强  罗明  马德英  张春竹 《植物保护》2022,48(6):207-213
梨火疫病(fire blight)是由解淀粉欧文氏菌Erwinia amylovora引起的蔷薇科果树毁灭性病害。2017年首次在新疆巴音郭楞蒙古自治州发生,对库尔勒香梨产业造成严重危害和经济损失。本文总结5年来库尔勒香梨火疫病发生危害特点,详细描述了病害的田间症状表现,提出了防治建议,并对当前库尔勒香梨火疫病防治中存在的问题进行了讨论。  相似文献   

19.
梨火疫病的进境风险分析   总被引：4，自引：1，他引：4  
讨论了梨火疫病的世界分布、国内苹果和梨的生产状况及经济重要性、梨火疫病在国内的适用性及国内外检测技术现状；澄清了以前我国有梨火疫病分布的错误报道。梨火疫病对我国梨和苹果生产具有极大的潜在风险，同时对我国的环境美化和生物多样性亦具潜在威胁。我国大部分地区为梨火疫病的适生区，国内广布梨火疫病的寄主。针对进口苗木的风险最大及果实亦可传病，提出了相应的风险管理措施。  相似文献   

20.
The fungal pathogen Monilinia fructicola causes blossom blight and fruit brown rot of stone fruits in California. In this study, spore densities in the air were monitored in six orchard/year combinations with Burkard spore traps. A real-time PCR assay was developed to efficiently quantify the dynamics of spore density in these orchards during the growing season. Different patterns of dynamics of spore density were observed in these orchards. A linear relationship between numbers of spores counted with a compound microscope and those determined with the real-time PCR assay was obtained, using the same samples of spore traps. Spore density in five of six orchard/year combinations ranged from 0.0 to 0.05 spores l−1, except for that in orchard 4, which showed much higher values of spore density in the air, as well as higher values and wider range of incidences of blossom infection and fruit rot than those in the other orchards. The results demonstrated a potential method to quantitatively determine spore inoculum potential in orchards by using a real-time PCR assay.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号