苹果黑星病在辽宁省的分布及其发生规律

苹果黑星病是辽宁省植物检疫对象。目前主要分布于小苹果栽植区及大、小苹果混栽区,已接近辽宁南部的大苹果主产区。经自然感病和人工接种证明,大、小苹果上的黑星病菌可以交互侵染,目前一些主栽的大苹果品种均能感染此病。辽宁地区苹果黑星病的初次侵染来源是落地越冬病叶上于翌春产生的子囊孢子。分生孢子不能越冬成活。苹果枝条及芽鳞不带菌。黑星病菌的两种孢子随气流传播,使病害逐步扩大蔓延。经过6年的观察,苹果黑星病发生始期早晚及发病轻重,与早春和夏季的降水量多少成正相关。田间药剂防治试验结果,以托布津、乙磷铝、多菌灵、特克多等药剂防治效果良好。     

黑龙江省小苹果黑星病Venturia inaequalis(cooke)winter的初侵染来源

 1958-1963年调查研究证明黑龙江省小苹果黑星病病叶上的分生孢子全部不能越冬。在早春也没有发现带病的枝条,因此以菌丝在病枝上越冬、春天产生分生孢子的可能性极小。每年春天在去年病树的干枯落叶上能找到大量子囊壳及子囊孢子,经人工接种后侵染率都极高。空中孢子捕捉的结果是:子囊孢子出现在前,分生孢子的出现是在田间发病以后,两者相距半个月以上,说明所捕捉到的分生孢子是受子囊孢子侵染后产生的。可以得出结论:黑龙江省小苹果黑星病的初次侵染来源是子囊孢子。
早期调查发病情况说明离地面越近的叶片发病越早,越重。初步认为,清扫落叶是减轻病害的重要措施之一。     

陕西苹果黑星病防治建议

苹果黑星病是由黑星病原引起的,是全世界苹果产区最重要的一种病害,严重发生时苹果损失可达７０％,并造成落叶影响来年果芽生长势。三年来,发现该病害在陕西渭北苹果产区有所发生,因此果农在制定防治计划时必须考虑该病害,将其控制在一定范围内并尽快消灭。在此作者提出：（１）春、初夏连续间隔一定时间适时喷药,并清洁果园以减少春季初侵染源是防治此病的关键,如何有侵染发生,夏季末及近收获季节应继续喷药;（２）推荐作     

苹果树的几种常见病害及其防治对策

在泰安地区，苹果栽培品种主要有富土、新红星、乔纳金、嘎啦和金冠。据1997～1999年调查发现苹果斑点落叶病、轮纹病和炭疽病等几种病害发生严重且呈逐年上升趋势。一般果园平均发病率为30％～50％，严重者可达70％，造成了巨大经济损失。1病原及为害　　1)斑点落叶病：该病病原菌主要是轮斑病菌(Alternariamali)的强毒株系。此病病原性很强，无伤接种可直接侵染叶片。菌丝体发育最适温度28℃，最适pH4.5～6。以菌丝体在病落叶上越冬，还可在枝上病斑、皮孔及芽鳞等处越冬。该病菌可以为害叶片、枝条和果实。在叶片上形成具紫色晕圈的病斑…     

小麦白粉病的流行规律及发生展望

1.小麦白粉病的流行区有三种类型:(1)以分生孢子继代越夏为主要型式的终年流行区;(2)以闭囊壳休眠越夏、子囊孢子主要侵染秋苗的秋苗带菌越冬流行区;(3)以闭囊壳越夏、越冬,子囊孢子在春季侵染的春季侵染流行区。2.白粉病的发病程度,主要决定于春季的流行速度,影响流行速度的因素是:(1)大面积种植感病品种、品种抗性的退化和病菌新生理小种的出现,是病害大流行的基础;(2)气候是影响年度间病情轻重的主导因素。10℃以上天气出现早,21℃以上高温出现迟,则发病期长、病情重。过程性降雨有利病菌孢子的繁殖与侵入。病情与气候的关系有:多雨限制     

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。     

黑星病菌有性阶段的特性与影响因素

梨黑星病(Venturia nashicola)和苹果黑星病(Venturia inaequalis)有性阶段假囊壳的产生与环境条件有密切的关系。假囊壳释放的子囊孢子是重要的初侵染菌源。其释放、萌发与侵染也和环境条件密切相关。防治黑星病最有效的措施是清除初侵染源,可根据子囊孢子造成侵染的条件制定防治方案。     

苹果斑点落叶病偏重发生原因与防治对策

永寿县地处陕西省渭北旱塬，全县栽植苹果近１．２万ｈｍ２。近年来苹果斑点落叶病逐年偏重发生，发病面积不断扩大，发病程度不断加重，已由次要病害上升为主要病害。该病具有潜育期短、发病早、扩展快、再侵染率高的特点。永寿县１９９７年零星发病面积约６００ｈｍ２，病叶率０．１％；１９９８年发病面积发展到２０００ｈｍ２，病叶率１１．２％；１９９９年发病面积达３３３３ｈｍ２，病叶率１７．１％；２０００年则上升到８６６７ｈｍ２，病叶率２６．５％，重发点位则达到１００％。近几年来，通过对斑点落叶病的发生与相关因素的调…     

黄瓜黑星病及其防治措施

黄瓜黑星病是黄瓜生产上近年发生的危险性病害 ,严重地影响黄瓜的产量和质量 ,病瓜重量下降 ,味变苦 ,完全失去食用价值。黄瓜黑星病为真菌性病害 ,病菌传播主要是种子带菌 ,其次是土壤带菌。本病发生和气温与湿度关系很大。病菌生长最适宜温度为１５～２５℃ ,低于５℃或高于３０℃不生长。相对湿度９３ %以上分生孢子产生 ,有水滴时分生孢子萌发。露地黄瓜黑星病的发生发展与当年的雨量和雨日有很大关系。夏季连续冷凉多湿天气容易发病。如果黄瓜定植后 ,遇雨日多或灌水过量 ,就容易发病并迅速蔓延。１发病症状１．１苗期发病发病率高低和…     

粉锈宁防治苹果白粉病研究初探

苹果白粉病是烟台苹果产区的重要病害,幼树新梢被害率高达50％以上。成龄果树越冬芽平均受害率为4.3％,重病果园花丛被害率达26.7％,发病高峰期新梢被害率达80％以上。新梢被害幼叶皱缩脱落,被害花芽座果率低,受害果实着生锈斑降为等外果。以往,防治苹果白粉病主要采用人工摘除病梢和喷布石硫合剂等措施,不能有效地控制为害,1982—1985年,我所进行了粉锈宁防此病的研究,并配合病区县市创造了60万亩防病示范区,取得了明显的防病增产效果,深受群众欢迎。研究结果初报于下。     

The relative importance of conidia and ascospores as primary inoculum of Venturia inaequalis in a southeast England orchard

Apple scab, caused by Venturia inaequalis, can lead to large losses of marketable fruit if left uncontrolled. The disease appears in orchards during spring as lesions on leaves. These primary lesions are caused by spores released at bud burst from overwintering sources; these spores can be sexually produced ascospores from the leaf litter or asexual conidia from mycelium in wood scab or within buds. The relative importance of conidia and ascospores as primary inoculum were investigated in an orchard in southeast England, UK. Potted trees not previously exposed to apple scab were placed next to (c. 1 m) orchard trees to trap air‐dispersed ascospores. Number and position of scab lesions were assessed on the leaves of shoots from both the potted trees (infection by airborne ascospores) and neighbouring orchard trees (infection by both ascospores and splash‐dispersed, overwintered conidia). The distribution and population similarity of scab lesions were compared in the two tree types by molecular analysis and through modelling of scab incidence and count data. Molecular analysis was inconclusive. Statistical modelling of results suggested that conidia may have contributed approximately 20–50% of the primary inoculum in early spring within this orchard: incidence was estimated to be reduced by 20% on potted trees, and lesion number by 50%. These results indicate that, although conidia are still a minority contributor to primary inoculum, their contribution in this orchard is sufficient to require current management to be reviewed. This might also be true of other orchards with a similar climate.     

苹果黑星病菌中国菌株生物学特性研究

 苹果黑星病菌(Venturia inaequalis(Cooke) Wint.)适合生长的培养基有苹果叶汁、苹果果汁、麦芽浸渍物、PSA、PDA、V8和马铃薯麦芽糖;适合产孢的培养基有苹果叶汁、V8和PSA。菌落生长和产孢适宜的pH值为5.0~6.5,温度为15~20℃。在碳源和氮源中,蔗糖、葡萄糖、果糖、麦芽糖、酵母提取物、硝酸钠和牛肉膏有利于病菌生长和产孢,硫酸铵抑制产孢,草酸铵抑制菌落的生长和产孢。20℃时,光周期为12 h,光照强度为600 lx条件下有利于病菌在PSA培养基上生长和产孢,其产孢量约为黑暗条件下的13倍。病菌分生孢子在水滴中萌发的适宜温度为20~25℃,最适pH值为5.0~6.5     

苹果黑星病菌遗传多样性的SSR分析

 Apple scab caused by Venturia inaequalis has a tendency to spread and threatens the development of apple production in recent years in China. The genetic diversity and population structure were investigated by using simple sequence repeat (SSR) markers. 51 strains were classified into 3 groups by UPGMA method as Xunyi, Xingping and U. K. population, each of them mainly including strains from its original place. A relatively high level of genetic diversity was revealed:H=0.425 3, I=0.675 8, PPL=66.67% (at species level); H=0.149 1, I=0.228 0, PPL=44.44% (at population level). A high level of genetic differentia-tion was detected among/within populations with Nei's Gst analysis and AMOVA. Molecular genetic variance within populations was greater than that among populations. Genetic variance among populations might result from barriers to gene flow (Nm=0.675 8). Genetic variance within populations might result from sexual propagation of V. inaequalis.     

Ascospores of the Japanese pear scab fungus (<Emphasis Type="Italic">Venturia nashicola</Emphasis> Tanaka &; Yamamoto) are discharged during the day

We investigated the diurnal pattern of ascospore discharge of the Japanese pear scab fungus (Venturia nashicola Tanaka & Yamamoto) in an orchard. Ascospores of V. nashicola were mainly discharged during the day. Most ascospores were discharged from 7:00 to 19:00: 99.6% in 2001, 99.3% in 2002, and 93.8% in 2005. Because the ascospores were discharged only when the fallen diseased leaves were wet from precipitation, the wetness of these leaves is probably imperative for spore discharge. Ascospore discharge began immediately after precipitation in the daytime. When it rained at night, however, ascospore discharge did not begin until the following morning and never began immediately after precipitation. We also investigated other meteorological factors. When fallen diseased leaves were wet, the percentage of ascospore discharge was positively correlated with the amount of solar radiation and atmospheric temperature and negatively correlated with relative humidity. Ascospore discharge was interrupted by a decrease in solar radiation and atmospheric temperature and by increased relative humidity at night. This report is the first that V. nashicola discharges ascospores primarily during the day.     

Ascospore Release and Infection of Apple Leaves by Conidia and Ascospores of Venturia inaequalis at Low Temperatures

ABSTRACT Mills' infection period table describes the number of hours of continuous leaf wetness required at temperatures from 6 to 25 degrees C for infection of apple leaves by ascospores of Venturia inaequalis and reports that conidia require approximately two-thirds the duration of leaf wetness required by ascospores at any given temperature. Mills' table also provides a general guideline that more than 2 days of wetting is required for leaf infection by ascospores below 6 degrees C. Although the table is widely used, infection times shorter than those in the table have been reported in lab and field studies. In 1989 a published revision of the table eliminated a potential source of error, the delay of ascospore release until dawn when rain begins at night, and shortened the times reported by Mills for ascospore infection by 3 h at all temperatures. Data to support the infection times below 6 degrees C were lacking, however. Our objective was to quantify the effects of low temperatures on ascospore discharge, ascospore infection, and infection by conidia. In two of three experiments at 1 degrees C, the initial release of ascospores occurred after 131 and 153 min. In the third experiment at 1 degrees C, no ascospores were detected during the first 6 h. The mean time required to exceed a cumulative catch of 1% was 143 min at 2 degrees C, 67 min at 4 degrees C, 56 min at 6 degrees C, and 40 min at 8 degrees C. At 4, 6, and 8 degrees C, the mean times required to exceed a cumulative catch of 5% were 103, 84, and 53 min, respectively. Infection of potted apple trees by ascospores at 2, 4, 6, and 8 degrees C required 35, 28, 18, and 13 h, respectively; substantially shorter times than previously were reported. In parallel inoculations of potted apple trees, conidia required approximately the same periods of leaf wetness as ascospores at temperatures from 2 to 8 degrees C, rather than the shorter times reported by Mills or the longer times reported in the revision of the Mills table. We propose the following revisions to infection period tables: (i) shorter minimum infection times for ascospores and conidia at or below 8 degrees C, and (ii) because both ascospores and conidia are often present simultaneously during the season of ascospore production and the required minimum infection times appear to be similar for both spore types, the adoption of a uniform set of criteria for ascosporic and conidial infection based on times required for infection by ascospores to be applied during the period prior to the exhaustion of the ascospore supply. Further revisions of infection times for ascospores may be warranted in view of the delay of ascospore discharge and the reduction of airborne ascospore doses at temperatures at or below 2 degrees C.     

Heterogeneity of the aerial concentration and deposition of ascospores of <Emphasis Type="Italic">Venturia inaequalis</Emphasis> within a tree canopy during the rain

Scab is an important disease of apple and its control depends almost exclusively on frequent use of fungicides. Primary scab infection in the spring assumes several steps: ascospore maturation, liberation of ascospores that become airborne, deposition on susceptible tissues, and infection. However, the spatial heterogeneity of ascospores within the tree canopy is unknown. Aerial concentration of ascospore (ACA), ascospore concentration in rain water (ACR) and ascospore deposition (AD) were therefore measured at six heights (20–257 cm from the ground) with rotating-arm air samplers, funnels, and greased glass slides, respectively, during five rain events in 2001 and in 2002. In addition, ACR and AD were measured at eight locations within tree canopy at 196 cm height. Apple scab was assessed at the end of the primary infection period in each sampling location within the apple tree. A similar experimental design was used in 2003 to study the spatial heterogeneity of both AD and primary scab lesions. ACA and AD decreased with increasing height, while ACR increased with increasing height. Based on both variance to mean ratio and the power law relationship in both years, the ACR was heterogeneous, while AD was heterogeneous only during the peaks of ascospore release. The ACR was significantly higher at the centre of the trees and the AD was significantly higher at the centre and at the western edge of the trees. Only the cumulative AD was significantly correlated with apple scab lesions at the same location (r = 0.83). In 2003, a similar pattern of spatial heterogeneity within the tree canopy was observed for AD and primary scab lesion counts and there was a linear relationship (R ² = 0.84) between these two variables. It was concluded that ACR and AD within the tree canopy are not randomly distributed at least during peaks of ascospore release and that AD is a good estimate of primary scab lesion development. This spatial heterogeneity should be considered when estimating ascospore deposition using mathematical models or when quantifying ascosporic inoculum using spore samplers.     

Effect of Fall Application of Fungal Antagonists on Spring Ascospore Production of the Apple Scab Pathogen, Venturia inaequalis

ABSTRACT The influences of Microsphaeropsis sp., M. arundinis, Ophiostoma sp., Diplodia sp., and Trichoderma sp., all antagonists of Venturia inaequalis, on ascospore production were evaluated under natural conditions and compared with urea and Athelia bombacina, a known antagonist. In the autumn, the fungi were applied to leaf disks artificially inoculated with V. inaequalis and to scabbed apple (Malus domestica) leaves incubated under controlled and natural conditions. In addition, large-scale trials were conducted with Microsphaeropsis sp. applied either as a foliar postharvest spray or as a ground application at 90% leaf fall. All fungal isolates, except Ophiostoma sp., were recovered from the leaf material that overwintered in the orchard. All treatments, except those with Ophiostoma sp., resulted in a significant reduction in V. inaequalis ascospore production on the leaf disks incubated under controlled conditions or in the orchard. In 1997, leaves with apple scab lesions treated with urea or Microsphaeropsis sp. produced significantly fewer ascospores of V. inaequalis than did nontreated leaves, with a reduction of 73.0 and 76.3%, respectively. In 1998, leaves treated with Microsphaeropsis sp., urea, Trichoderma sp., A. bombacina, and M. arundinis reduced ascospore production by 84.3, 96.6, 75.2, 96.6, and 52.2%, respectively. Based on all tests combined, the most efficient isolate was Microsphaeropsis sp. Postharvest applications of Microsphaeropsis sp. reduced the total amount of airborne ascospores trapped by 70.7 and 79.8% as compared with the nontreated plots in 1997 and 1998, respectively. Microsphaeropsis sp. provided a significant and consistent reduction in ascospore production in all tests.     

Effect of Timing of Application of the Biological Control Agent Microsphaeropsis ochracea on the Production and Ejection Pattern of Ascospores by Venturia inaequalis

ABSTRACT Field and in vitro trials were conducted to establish the influence of the biological control agent Microsphaeropsis ochracea on the ejection pattern of ascospores by Venturia inaequalis and on apple scab development, and to establish the best timing of application. The ejection pattern of ascospores was similar on leaves sprayed with M. ochracea and on untreated leaves. Fall application of M. ochracea combined with a delayed-fungicide program was evaluated in orchards with intermediate and high scab risk. For both orchards, it was possible to delay the first three and two infection periods in 1998 and 1999, respectively, without causing significant increase or unacceptable leaf and fruit scab incidence. To evaluate the best timing of application, sterile leaf disks were inoculated with V. inaequalis and then with M. ochracea 0, 2, 4, 6, 8, 10, 12, 14, and 16 weeks later. After incubation under optimal conditions for pseudothecia development, the number of ascospores was counted. Similarly, M. ochracea was sprayed on scabbed leaves on seven occasions from August to November 1999 and 2000. Leaves were overwintered on the orchard floor and ascospore production was evaluated the following spring. Ascospore production was reduced by 97 to 100% on leaf disks inoculated with M. ochracea less than 6 weeks after inoculation with V. inaequalis, but ascospore production increased with increasing period of time when M. ochracea was applied 8 to 16 weeks after the inoculation with V. inaequalis. In the orchard, the greatest reduction in production of ascospores (94 to 96% in 2000 and 99% in 2001) occurred on leaves sprayed with M. ochracea in August. The production of ascospores was reduced by 61 to 84% in 2000 and 93% in 2001 on leaves sprayed with M. ochracea in September, reduced by 64 to 86% in 2000 and 74 to 89% in 2001 on leaves sprayed in October, and reduced by 54 and 67% in 2000 and 2001, respectively, on leaves sprayed in November. It was concluded that M. ochracea should be applied in August or September and that ascospore maturation models and delayed-fungicide program could be used in orchards treated with this biological control agent.     

温度、湿度和光照对苹果炭疽叶枯病菌(Glomerella cingulata)产孢的影响

苹果炭疽叶枯病(Glomerella cingulata)是我国苹果上新发现的一种病害,为了了解病原菌的产孢条件和产孢动态,为病害的预测预报与防控提供依据。本研究在人工控制条件下,测试了温度、湿度和光照对苹果炭疽叶枯病菌产生分生孢子和子囊孢子的影响。结果表明,苹果炭疽叶枯病新形成的病叶润湿后,在15℃~30℃下保湿培养2~6 d后可产生大量橘黄色的分生孢子堆,其中30℃下产孢量最大,产孢速度最快,仅需2 d时间。炭疽叶枯病菌在新形成的病叶上于15℃~30℃下培养20~30 d可形成子囊孢子,最适温度为25℃,子囊孢子的形成需要高湿环境或叶片润湿。炭疽叶枯病菌的单孢分离菌株于15℃~25℃下,在马铃薯葡萄糖琼脂培养基(PDA)上培养20~30 d也可形成子囊孢子,最适产孢温度25℃。紫外光、黑光和日光都能促进子囊孢子的形成。     

Selection and orchard testing of antagonists suppressing conidial production by the apple scab pathogen <Emphasis Type="Italic">Venturia inaequalis</Emphasis>

Apple scab caused by Venturia inaequalis is a major disease in apple production. Epidemics in spring are initiated by ascospores produced on overwintering leaves whereas epidemics during summer are driven by conidia produced on apple leaves by biotrophic mycelium. Fungal colonisers of sporulating colonies of V. inaequalis were isolated and their potential to reduce the production of conidia of V. inaequalis was evaluated on apple seedlings under controlled conditions. The four most effective isolates of the 63 screened isolates were tested subsequently under Dutch orchard conditions in 2006. Repeated applications of conidial suspensions of Cladosporium cladosporioides H39 resulted in an average reduction of conidial production by V. inaequalis of approximately 40%. In 2007, applications of conidial suspensions of C. cladosporioides H39 reduced conidial production by V. inaequalis by 69% on August 6 and by 51% on August 16, but no effect was found on August 20. However, viability of available conidia of C. cladosporioides H39 was low at the end of the experiment. Epiphytic and endophytic colonisation by Cladosporium spp. of leaves treated during the experiment with C. cladosporioides H39 was significantly higher than on control leaves sampled 6 weeks after the last application. It is concluded that C. cladosporioides H39 has promising potential as a biological control agent for apple scab control. More information is needed on the effect of C. cladosporioides H39 on apple scab epidemics as well as on mass production, formulation and shelf life of conidia of the antagonist.