陕西关中地区梨黑星病的发生与防治

梨黑星病在陕西关中地区为害非常严重,经常在6—7月间流行,引起巨大损失。当冬季干燥寒冷时,病菌主要以落叶上残存的分生孢子过冬,但是如果遇上潮湿温暖的冬季便可大量形成子囊壳;至于病菌能否在病梢、病芽内外越冬的问题,初步试验结果是否定的。病害流行与降雨及温度的关系最为密切,潜育期为12—29天,具体情况随气温而定;另外还初步提出了病害初次侵染与续发侵染的预测条件。在武功采集到另一类型的梨黑星病菌,其特点是分生孢子梗非常细长,上面的瘤状物也较突出明显;推测可能同于 Venturia inaequalis f.piri Hara。喷射1∶1∶160式波尔多液并结合进行清园,减少越冬菌源及加强栽培管理,提高树势等项工作对病害防治具有优良效果。     

辽宁梨黑星病的防治

辽宁省是我国主要梨产区之一,近年发展尤为迅速,总株数近4000万株,年产量32万余吨。近几年,梨黑星病发生十分普遍,为害相当严重。防治该病已成为梨树生产上的一项重要工作。1 症状梨黑星病主要为害叶片及果实,其症状特点是在病部产生黑色霉状物。叶片受害多先发生于叶背面,在叶脉上形成长条形黑色霉斑。在叶表面的叶脉间产生近圆形褪绿斑,不久病斑上长出初为绿褐色后变黑色的霉状     

我国北方梨黑星病的发生危害及防治对策

我国北方梨黑星病的发生危害及防治对策李保华，赵美琦（山东菜阳农学院植保系２６４２００）（北京农业大学植保系）董向丽（菜阳农学院植保系）１９９３年８－１０月，作者对河北石家庄、昌黎，山东菜阳、，黄县、文登，北京大兴等地近年梨黑星病的发生与危害作了调查，...     

2001年梨黑星病大发生原因及防治对策

经观察和调查,描述了梨黑星病在黄河故道地区的症状表现,分析了2001年大发生的原因,提出了防治对策。     

防治梨黑星病的技术要点

为防治梨黑星病，各个果园都投入了大量人力、物力进行多次施药，但有的果园并未取得好的防效。究其原因有多种可能：①用药不当，未在关键时期施药，病害失控；②病菌对有些杀菌剂已有抗性，虽按要求施用，防效下降；③对新的高产内吸杀菌剂品种应用技术未能深刻领会。实质是对病原菌的越冬、早春初发生、流行的气候条件等所知不多，抓不住防治关键，再加上对药剂使用技术不精等原因综合而成的结果。     

河北廊坊市鸭广梨暴发梨黑星病

固安县北义后村是一个有百余年生产历史的鸭广梨产区,有混植梨园1000余亩。其中鸭广梨树占梨树总数的80％,其产量产值占梨产量产值总数的90％以上。另外零星分布有少量鸭梨、京白梨等。是一个以盛产鸭广梨为特点的果树专业村。1982-1989年,该村的鸭梨、京白梨每年都因梨黑星病发生造成不同程度损失:而鸭广梨很少见到病果,果实商品率一般可达90％以上。1990年该     

梨抗黑星病AFLP标记筛选

 Pear scab caused by Venturia nashicola is one of the most destructive diseases of pears. Molecular markers linked to scab resistance gene is expected to be useful for improving pear. In this study, the F₁ population derived from the cross of ‘Huangguan’ and ‘Yali’ was analyzed genetically. The resistance of pear to scab was proved to be controlled by a single gene in a dominant manner. Bulked segregant analysis (BSA) was conducted to screen 64 fluorescent AFLP primer pairs. A marker designated as D3-365 was found to be linked to the resistant locus. Selective genotype linkage analysis showed that the genetic distance between the marker and the resistant locus was 14.9 cM.     

花期前喷药防治梨黑星病

为了防止梨黑星病早期发生,我们试验在梨树开花前喷波尔多液,有显著效果。 试验是在东代固大队,27年生梨园内进行,品种为鸭梨,树势衰弱,1963年感黑星病较重,病果率为75％。处理方法见下表:     

梨黑星病流行动态模拟模型程序设计

梨黑星病流行动态模拟模型(PSSM)能以一日为一个步长模拟整个生长季节梨黑星病的流行动态。PSSM的计算机程序采用了面向对象的程序设计。模型中,梨园每一天的状态,如寄主、病原物的相对数量,果园环境的温度、湿度,果园管理措施等,由一个果园状态对象表示。果园状态对象由18个子对象和10个子模型构成。18个子对象分别表示寄主、病原物的相对数量、果园环境条件和管理措施等。10个子模型模拟孢子传播、侵染、病斑显症等病害流行动态过程。模型运行时,子模型根据果园前期状态和当日环境,计算获得数据,创建表示当日果园状态的对象,并依次类推。程序结构清晰自然,能较好地再现病害发生与流行的生物学过程。     

无公害药剂防治梨黑星病药效试验

莱阳梨肉嫩质细,清脆可口,香浓味美,驰名中外。梨黑星病Venturia Pirina(Cooke) Aderh是莱阳梨的重要病害之一,每年受害面积达1667hm2,占全市栽培梨园面积的90%以上。梨黑星病主要危害叶片和果实,叶片受害后,在叶片背面产生圆形或不规则淡黄色病斑,潮湿环境下,产生黑色霉层。果实在直径1cm大小就可受害,病斑圆形,随着果实的增长,     

辣椒疫病发病主导因素及综合防治技术研究

通过3a在多年辣椒重茬地的田间试验及调查研究,基本明确了辣椒疫病发生与灌水方法、栽培方式、降水、中心病株的出现等主导因素的关系。提出了栽培防病、化学治疗的综防技术,达到控病增产的目的。     

果树小蠹是桃树流胶病发生的主要原因

１９９６年以来，山东省胶东地区桃园流胶病偏重至大发生。桃树流胶病成为桃树生产的最重要病害之一。流胶病大发生的症状是大量胶体自桃树主干及枝条上的皮目等处流出，桃树树体因为大量流胶而衰弱并死亡。按照传统理论，桃树流胶病系生理性病害。也有报道系真菌性病害。１９９８年以来，通过我们系统观察，发现桃树枝干流胶的成因主要系一鞘翅目小昆虫在枝干表皮至韧皮部大量蛀食为害造成，蛀孔破坏了枝干输导组织，树液不能正常输送，自蛀孔流出，形成流胶病。据２００２年９月上旬标记观察，果树小蠹成虫为害的蛀孔２４h内流胶率达到９…     

即墨市麦蚜近年发生轻主要原因是生态控制的分析

1995～2004年10年间,即墨市麦蚜的防治由大量用药减为不用药,防治次数由每年2～3次减为0次。近3年,全市很少用药防治,麦蚜发生程度由大发生减为小发生,天敌的储存数量明显增加。实践证明,生态控制的重要性。     

Sensitivity of Venturia inaequalis to trifloxystrobin

The sensitivity of Venturia inaequalis to trifloxystrobin was monitored by both in vitro (spore germination) and in vivo tests (on apple seedlings). There was good correlation between the in vitro and in vivo results. Baseline sensitivity was established with 95 bulk isolates from Europe between 1995 and 1998 which showed a narrow sensitivity range-factor of up to 17 between the least and most sensitive isolates. Monitoring of populations originating from trifloxystrobin-treated and untreated orchards between 1995 and 1999 showed only sensitive isolates and no performance deficiencies were reported. Data also show that trifloxystrobin is not cross-resistant to anilinopyrimidines and triazoles, but is cross-resistant to kresoxim-methyl, another strobilurin which also inhibits the cytochrome bc1 enzyme complex at the Qo-site in the respiration chain of fungal mitochondria (QoI inhibitors). Under experimental conditions from a specific trial site in Switzerland, where trifloxystrobin has been tested since 1994, isolates containing conidia resistant to Qo inhibitors were detected in 1997 and 1999. However no obvious performance deficiencies were reported. Nevertheless these results demonstrate a risk for the development of practical resistance in V inaequalis to Qo inhibitors and therefore a need to apply resistance management principles strictly.     

农田害鼠发生主要影响因子调查分析

围场县地处河北省最北部,东、北部毗邻内蒙古。全县总面积9219km2。其中农业耕地8.13万hm2,农牧交错区20万hm2。农田害鼠常年发生面积20万hm2。其中农田发生面积8万hm2,达到防治指标面积2.7万hm2;农牧交错区发生12万hm2,达到防治指标的面积5.3万hm2。常年鼠平均密度450只/百亩,     

Germinability of Venturia inaequalis Conidia Exposed to Sunlight

ABSTRACT Detached conidia of Venturia inaequalis were exposed simultaneously outdoors to direct sunlight or in an adjacent ventilated enclosure in darkness for periods ranging from 0.5 to 16.5 h. In addition, conidia were either exposed or not exposed to UV light (254 nm) from 1 to 64 min in the laboratory. After exposure, conidia were placed on water agar in closed petri dishes and allowed 24 h to germinate. Germinability of conidia in the laboratory was reduced up to 95% by doses of UV(254) of 8.1 to 10.8 kJ m(-2).Germinability of conidia in the field was reduced up to 95% by doses of UV-B of about 44 kJ m(-2). A significant percentage of conidia survived radiation doses equivalent to 12 h in full sunlight.     

Negative cross-resistance to N-phenylanilines in benzimidazole- resistant strains of Botrytis cinerea,Venturia nashicola and Venturia inaequalis

A new series of compounds with high contra-selective activity against benomyl-resistant fungal strains was found among ring-substituted N-phenyl-anilines. Hydrophobic substitution in one of the benzene rings, together with the secondary amine character of the molecule, are important factors for high fungitoxicity. The sensitivities of benomyl-resistant isolates to some representatives of the N-phenylanilines equal or even surpass their sensitivity to diethofencarb or MDPC. The negative cross-resistance with benzimdazole fungicides is valid for strains of Botrytis cinerea, Venturia nashicola and Venturia inaequalis. The strains of B. cinerea with double insensitivity to benzimidazoles and phenyl-carbamates are insensitive also to N-phenylanilines. However, the similarly double-insensitive strain of V. nashicola was found to be just as sensitive to the N-phenylanilines tested as the strain resistant only to benzimidazoles. The latter result revealed an important bonus compared with diethofencarb. Preventive application of one of the most active representatives of the N-phenylanilines to young cucumber plants was effective against infection with benomyl-resistant isolates of B. cinerea. Moderate apical translocation after root-dipping was also observed.     

Effects of environmental factors on discharge and germination of ascospores of Venturia nashicola

Experiments were conducted under controlled environmental conditions to study the effects of temperature, duration of wetness, relative humidity (RH) and light on the discharge and germination of ascospores of Venturia nashicola , the causal agent of pear scab in China. Discharge of ascospores from pseudothecia required free water or 100% RH. A period of soaking in water as short as 10 s was sufficient to initiate the discharge of ascospores. Temperatures from 10 to 30°C did not significantly affect the temporal trend of ascospore discharge. A greater proportion of ascospores was discharged under light than in the dark. However, a period of light as short as 10 min, either during the initial wetting of pseudothecia or interrupting the darkness, was sufficient to reduce the inhibitory effect of darkness on ascospore discharge. Ascospores were discharged within 10 min after pseudothecia were wetted and most ascospores ( c. 80%) were discharged within the first hour. The temporal pattern of ascospore discharge could be well described by a logistic model, which estimated that 50% of ascospores were discharged within half an hour of wetting. Ascospores germinated over a wide range of temperatures from 5 to 30°C, with an optimum at c . 20°C. Temporal dynamics of ascospore germination at six temperatures (5, 10, 15, 20, 25 and 30°C) were satisfactorily described by logistic models.     

Characterization of Ribosomal DNA from Venturia inaequalis and Its Phylogenetic Relationship to rDNA from Other Tree-Fruit Venturia Species

ABSTRACT A portion of the 18S ribosomal DNA (rDNA) gene, the internal transcribed spacers (ITS1 and ITS2), and the 5.8S rDNA gene were polymerase chain reaction-amplified from strains and field populations of Venturia inaequalis and assessed for genetic variation. A previously reported optional group I intron in the 18S rDNA gene of V. inaequalis was detected in 75.0% of 92 strains collected worldwide and in 61.1 and 71.2% of 54 and 59 strains from two Michigan orchards, respectively. Sequence and restriction analysis of rDNA revealed four intron alleles, three of which were present both in worldwide strains and in each field population. Two ITS1 alleles were detected and found to be linked to specific intron alleles. The ITS1-5.8S-ITS2 sequences from V. asperata V. carpophila, V. cerasi, V. inaequalis, V. nashicola, V. pyrina, and Cladosporium caryigenum were compared using phylogenetic analysis. Strains of the Venturia species were placed in three distinct monophyletic groups in a phylogenetic tree. The first group comprised V. inaequalis; the second, V. pyrina and V. nashicola; and the third, V. cerasi, V. carpophila, and V. asperata. The described intron and ITS1 alleles in V. inaequalis provide genetic markers for subdividing populations of V. inaequalis, and the ITS1-5.8S-ITS2 sequences are valuable in determining the relationship of the species from tree-fruit crops with other Venturia species.     

Differential responses of germinating Venturia inaequalis conidia to kresoxim-methyl

A new class of agricultural fungicides derived from strobilurins act as respiration inhibitors by binding to mitochondrial cytochrome b. The effects of the strobilurin, kresoxim-methyl, on conidia germination, mycelial growth and the protection of apple leaves from scab development were investigated for two isolates of Venturia inaequalis randomly selected from a culture collection. Inhibition of mycelial growth required relatively high doses of kresoxim-methyl (ED₅₀=1 μg ml^-1) for both isolates. In comparison, germination of conidia was highly sensitive for one of the isolates (ED₅₀=0·005 μg ml^-1), while the level of inhibition achieved for the second isolate was 60-fold less (ED₅₀=0·3 μg ml^-1). As deduced from identical sequences of cytochrome b cDNAs prepared from both isolates, the different responses of germinating conidia to kresoxim-methyl were not caused by differences in the sequence of cytochrome b as the target site for strobilurin action. Strong synergistic effects of salicylhydroxamic acid on kresoxim-methyl inhibitory potency suggested that the reduced kresoxim-methyl sensitivity observed for germinating conidia was caused by interference of the alternative respiratory pathway with inhibitor action. However, this mechanism of target site circumvention in germinating conidia had no adverse effects on the protection of apple leaves from scab infection by kresoxim-methyl. © 1998 Society of Chemical Industry