Disease-weather relationships for powdery mildew and yellow rust on winter wheat

Key weather factors determining the occurrence and severity of powdery mildew and yellow rust epidemics on winter wheat were identified. Empirical models were formulated to qualitatively predict a damaging epidemic (>5% severity) and quantitatively predict the disease severity given a damaging epidemic occurred. The disease data used was from field experiments at 12 locations in the UK covering the period from 1994 to 2002 with matching data from weather stations within a 5 km range. Wind in December to February was the most influential factor for a damaging epidemic of powdery mildew. Disease severity was best identified by a model with temperature, humidity, and rain in April to June. For yellow rust, the temperature in February to June was the most influential factor for a damaging epidemic as well as for disease severity. The qualitative models identified favorable circumstances for damaging epidemics, but damaging epidemics did not always occur in such circumstances, probably due to other factors such as the availability of initial inoculum and cultivar resistance.     

A dynamic simulation model for powdery mildew epidemics on winter wheat*

A system dynamic model for epidemics of Blumeria graminis (powdery mildew) on wheat was elaborated, based on the interaction between stages of the disease cycle, weather conditions and host characteristics. The model simulates the progress of disease severity, expressed as a percentage of powdered leaf area, on individual leaves, with a time step of one day, as a result of two processes: the growth of fungal colonies already present on the leaves and the appearance of new colonies. By means of mathematical equations, air temperature, vapour pressure deficit, rainfall and wind are used to calculate incubation, latency and sporulation periods, the growth of pathogen colonies, infection and spore survival. Effects of host susceptibility to infection, and of leaf position within the plant canopy, are also included. Model validation was carried out by comparing model outputs with the dynamics of epidemics observed on winter wheat grown at several locations in northern Italy (1991–98). Simulations were performed using meteorological data measured in standard meteorological stations. As there was good agreement between model outputs and actual disease severity, the model can be considered a satisfactory simulator of the effect of environmental conditions on the progress of powdery mildew epidemics.     

Relating disease progress to cumulative numbers of trapped spores: apple powdery mildew and scab epidemics in sprayed and unsprayed orchard plots

A technique for relating the progress of plant diseases caused by airborne fungal pathogens to cumulative numbers of trapped spores is proposed. The relationship involves two epidemiological parameters—a disease asymptote and the infection efficiency (disease units/spore) of inoculum. The technique was evaluated using data on apple powdery mildew and scab epidemics in sprayed and unsprayed apple orchard plots. For powdery mildew, the observed relationships were close to those proposed in the unsprayed plot, but changed after or during the period of fungicide application in sprayed plots. Parameter estimates gave useful comparative information on the epidemics. The technique was not useful for scab because of the discontinuous patterns of infection.     

PC-based disease warning systems for use by apple growers1

To protect apple orchards from diseases efficiently, growers need farm-based rather than regional disease warning systems. This paper describes three PC-based systems from Horticulture Research International (GB). These systems, VENTEM, PODEM and NECTEM, provide warnings in the form of infection alerts and disease forecasts of Venturia inaequalis (scab), Podosphaera leucotricha (powdery mildew) and Nectria galligenu (European canker and fruit rot), respectively. The modular structure, operation and practical implementation of these systems are described and compared. A major input is weather data recorded automatically by Metos weather stations sited on farms. Each system has a weather-driven dynamic model simulating inoculum production and the infection process. The systems use information on quantity of inoculum, cultivar susceptibility and other host factors to produce disease forecasts which are specific to individual orchard blocks and cultivars.     

室内模拟塑料大棚黄瓜白粉病流行预测模型的建立

在室内人工气候箱内,通过人工接种和模拟高温高湿环境的方法研究了黄瓜白粉病的发生和流行趋势,采用SAS统计软件对试验数据进行相关和回归分析,建立了黄瓜白粉病始病期与流行程度的预测模型。始病期预测模型的RMSE值在2以下,流行程度预测模型的RMSE值在6以下,表明模型可对塑料大棚黄瓜白粉病始病期和流行程度进行定量预测。     

Conditions for development of powdery mildew of tomato caused by Oidium neolycopersici

Oidium neolycopersici causes severe powdery mildew on all aerial parts of tomato, excluding the fruit. The objective of the present work was to examine factors that influence the development of O. neolycopersici on tomato and to identify potential methods for managing tomato powdery mildew. Under controlled conditions, the highest rates of conidial germination were observed at 25 degrees C, 99% relative humidity (RH) and minimal light, and the lowest on leaves adjacent to fruits. Optimal conditions for appressoria formation were 25 degrees C, RH ranging from 33 to 99%, and 1,750 lux light intensity. More conidia were formed at 20 degrees C, 70 to 85% RH, and 5,150 lux light intensity than at 16 and 26 degrees C, 99% RH, and 480 to 1,750 lux, respectively. Conidia survived and remained capable of germination for over four months when initially incubated at lower temperatures and higher RH, as compared with their fast decline under more extreme summer shade conditions. In growth chamber experiments, disease did not develop at 28 degrees C. Within the range of 70 to 99% RH, disease was less severe under the higher RH than the drier conditions. Disease was also less severe at lower light intensities. Data collected in three commercial-like greenhouse experiments involving various climate regimes were used to draw correlations regarding the effects of temperature and RH on the development of epidemics. Severity of powdery mildew was positively correlated with the duration of the range 15 to 25 degrees C, 1 to 4 weeks before disease evaluation (BDE), RH levels of 60 to 90% at 2 to 4 weeks BDE, and RH of 50 to 60% during the week BDE. Conversely, disease was negatively correlated with the duration of temperatures in the low and high ranges (5 to 15 degrees C and 35 to 40 degrees C) at 1 to 4 weeks BDE, with the duration of RH levels of 40% and below at 1 to 4 weeks BDE, and with 50 to 60% RH during the third week BDE. High (90 to 100%) RH was also negatively correlated with disease severity. These results suggest that the combination of high temperatures and low RH may help reduce O. neolycopersici powdery mildew severity in greenhouse tomatoes.     

Problems in Modelling Powdery Mildew Epidemics1

We present some subsystems of a model describing epidemics of barley powdery mildew. In these phases of the pathogen's life cycle, both the weather and the host affect disease development. The reaction of the host changes dependent on the leaf position due to adult plant resistance. Some consequences and problems due to this fact are discussed. Disease must be simulated separately on each leaf. Functions used to describe a certain process may not be valid for all leaf positions. It may be necessary to take into account the variation in temperature of different leaves. According to weather conditions, adult-plant resistance can change and its development must be also modelled.     

Effects of sunlight exposure on grapevine powdery mildew development

Natural and artificially induced shade increased grapevine powdery mildew (Erysiphe necator) severity in the vineyard, with foliar disease severity 49 to 75% higher relative to leaves in full sun, depending on the level of natural shading experienced and the individual experiment. Cluster disease severities increased by 20 to 40% relative to those on check vines when ultraviolet (UV) radiation was filtered from sunlight reaching vines in artificial shading experiments. Surface temperatures of leaves in full sunlight averaged 5 to 8°C higher than those in natural shade, and in one experiment, filtering 80% of all wavelengths of solar radiation, including longer wavelengths responsible for heating irradiated tissues, increased disease more than filtering UV alone. In controlled environment experiments, UV-B radiation reduced germination of E. necator conidia and inhibited both colony establishment (hyphal formation and elongation) and maturity (latent period). Inhibitory effects of UV-B radiation were significantly greater at 30°C than at 20 or 25°C. Thus, sunlight appears to inhibit powdery mildew development through at least two mechanisms, i.e., (i) UV radiation's damaging effects on exposed conidia and thalli of the pathogen; and (ii) elevating temperatures of irradiated tissues to a level supraoptimal or inhibitory for pathogen development. Furthermore, these effects are synergistic at temperatures near the upper threshold for disease development.     

Seed treatment for the control of Sphaerotheca fuliginea in muskmelon seedlings

The effects of powdery mildew (caused by Sphaerotheca fuliginea )on muskmelon seedlings and the efficacy of seed treatment with systemic fungicides were examined under controlled environmental conditions. The fresh weight of seedlings infected with powdery mildew was substantially less than that of uninoculated seedlings 5 weeks after inoculation, and the inoculated seedlings shrivelled 1 week later. The fungicides fenarimol and triadimenol applied to the seeds did not affect germination and suppressed powdery mildew effectively when applied at a rate equivalent to 8 g fungicide product per kg seed. Under conditions moderately conducive to the pathogen, fenarimol markedly reduced disease severity and its effect when applied as a seed treatment was as effective as foliar treatment. When conditions were highly conducive to the pathogen, seed treatment with fenarimol was not effective. Development of powdery mildew and efficacy of the seed treatments were related to soil type: disease developed earlier and more intensely on seedlings grown in sandy soil than those in organic medium, and seed treatment had a more pronounced effect on seedlings grown in sandy soil. The results indicate that fungicidal treatment of muskmelon seeds may offer an adequate means of reducing powdery mildew infections on seedlings.     

近年我国重要苹果病害发生概况及研究进展

苹果是我国最重要的经济作物之一,截至2015年我国苹果种植面积达到232万hm~2,总产量超过4 200万t。各种病害仍是困扰我国苹果产业健康发展的限制性因素。腐烂病和枝干轮纹病依然是我国苹果最重要的枝干病害,斑点落叶病和白粉病连年发生,危害加重;霉心病在一些产区成为产业发展的限制性因素。病毒病病原种类还在增加,发生程度不断加重,已经上升为苹果主要病害。随着老果园重建的大范围开展,再植病害已经成为苹果产业可持续发展的障碍;缺素、裂果和冻害等非侵染性病害虽然不具传染性,但近年来发生面积不断扩大,对苹果产量的威胁在某些年份甚至较侵染性病害更为严重。本文系统总结了自2013年以来这些苹果主要病害的发生概况及研究进展,并分析了目前存在的问题,提出了相应的建议。     

Effects of humidity on the development of grapevine powdery mildew

ABSTRACT The effects of humidity on powdery mildew development on grape seedlings and the germination of Uncinula necator conidia in vitro were examined. Studies were conducted at an optimum temperature of 25 +/- 2 degrees C. Disease on foliage was markedly affected by humidity levels in the test range of 39 to 98% relative humidity (RH), corresponding to vapor pressure deficits (VPD) of 1,914 to 61 Pa. Incidence and severity increased with increasing humidity to an optimum near 85% RH, and then appeared to plateau or decrease marginally at higher values. Conidial density and chain length also were proportional to humidity, but were influenced less strongly. There was a strong, positive linear relationship between humidity level and frequency of conidium germination with RH treatments of 相似文献   

生防菌株LB-1培养液对黄瓜的抑病促生作用

 LB-1为新筛选的生防近缘毛壳(Chaetomium subaffine)菌株。为明确LB-1培养液的抑病促生效果,本研究以黄瓜为供试植物,分别采用灌根和叶面喷施的方式,测定了LB-1培养液对黄瓜枯萎病和黄瓜白粉病的抑制效果;通过种子萌发、盆栽苗和生化检测试验,分析了LB-1培养液对黄瓜的促生作用。结果发现,LB-1培养液对黄瓜枯萎病抑制作用效果甚微,但对黄瓜白粉病生防效果明显,黄瓜叶片接菌24 h后叶面喷施LB-1培养液对白粉病的防效高达48.86%。LB-1培养液浸润催芽处理24 h的黄瓜种子萌发率和根长均显著高于对照(P=0.05),且LB-1培养液浸种、灌根、叶面喷施处理均能促进黄瓜幼苗的生长发育。LB-1没有产嗜铁素、产氢氰酸、固氮和溶磷能力,但能够产生吲哚乙酸(Indoleacetic acid,IAA)。表明生防菌株LB-1培养液能有效抑制黄瓜白粉病的发生,促进黄瓜种子萌发和植株生长,而且其促生作用可能通过产生IAA来实现。     

生防菌株LB-1培养液对黄瓜的抑病促生作用

 LB-1为新筛选的生防近缘毛壳(Chaetomium subaffine)菌株。为明确LB-1培养液的抑病促生效果,本研究以黄瓜为供试植物,分别采用灌根和叶面喷施的方式,测定了LB-1培养液对黄瓜枯萎病和黄瓜白粉病的抑制效果;通过种子萌发、盆栽苗和生化检测试验,分析了LB-1培养液对黄瓜的促生作用。结果发现,LB-1培养液对黄瓜枯萎病抑制作用效果甚微,但对黄瓜白粉病生防效果明显,黄瓜叶片接菌24 h后叶面喷施LB-1培养液对白粉病的防效高达48.86%。LB-1培养液浸润催芽处理24 h的黄瓜种子萌发率和根长均显著高于对照(P=0.05),且LB-1培养液浸种、灌根、叶面喷施处理均能促进黄瓜幼苗的生长发育。LB-1没有产嗜铁素、产氢氰酸、固氮和溶磷能力,但能够产生吲哚乙酸(Indoleacetic acid,IAA)。表明生防菌株LB-1培养液能有效抑制黄瓜白粉病的发生,促进黄瓜种子萌发和植株生长,而且其促生作用可能通过产生IAA来实现。     

Predicting severity of asian soybean rust epidemics with empirical rainfall models

ABSTRACT Although Asian soybean rust occurs in a broad range of environmental conditions, the most explosive and severe epidemics have been reported in seasons with warm temperature and abundant moisture. Associations between weather and epidemics have been reported previously, but attempts to identify the major factors and model these relationships with field data have been limited to specific locations. Using data from 2002-03 to 2004-05 from 34 field experiments at 21 locations in Brazil that represented all major soybean production areas, we attempted to identify weather variables using a 1-month time window following disease detection to develop simple models to predict final disease severity. Four linear models were identified, and these models explained 85 to 93% of variation in disease severity. Temperature variables had lower correlation with disease severity compared with rainfall, and had minimal predictive value for final disease severity. A curvilinear relationship was observed between 1 month of accumulated rainfall and final disease severity, and a quadratic response model using this variable had the lowest prediction error. Linear response models using only rainfall or number of rainy days in the 1-month period tended to overestimate disease for severity <30%. The study highlights the importance of rainfall in influencing soybean rust epidemics in Brazil, as well as its potential use to provide quantitative risk assessments and seasonal forecasts for soybean rust, especially for regions where temperature is not a limiting factor for disease development.     

苦瓜白粉病病原菌和生理小种的鉴定及苦瓜对白粉病的抗性遗传分析

为明确海南省苦瓜白粉病的病原菌、生理小种及苦瓜对白粉病的抗性遗传规律,结合形态学鉴定和分子鉴定解析白粉病菌及生理小种种类,通过显微镜观察白粉病菌侵染过程,并应用主基因+多基因混合遗传模型分析法探讨苦瓜对白粉病的主要抗性遗传规律。结果表明:采集自海南省6个市(县)的苦瓜白粉病病原菌均为单囊壳白粉菌Sphaerotheca fuliginea,属生理小种2F,该菌在侵染苦瓜叶片时有4个关键时期:接种后4 h为分生孢子萌发高峰期,8 h为附着孢形成高峰期,16～24 h为次生菌丝形成高峰期,5 d为分生孢子梗形成高峰期。将其接种于苦瓜抗、感品系,对白粉病的抗性符合2对加性-显性-上位性主基因+加性-显性多基因模型,主基因和多基因共同控制苦瓜对白粉病的抗性,其中以主基因遗传为主,且会受到环境变异的影响。根据苦瓜抗性遗传规律,F2代主基因遗传率最高,受环境影响最小,在苦瓜的白粉病抗性育种中,以早期世代F2代作为有效选择世代。研究表明白粉病菌侵染叶片的前2 d是白粉病防治的最佳时期,所以在白粉病易发的物候期,可将防治时间提前1～2 d。     

Neue Erkenntnisse zur Biodiversität des Apfelmehltau-Erregers

Apple powdery mildew is one of the main fungal diseases in commercial apple production. High amounts of fungicides are applied to reduce the damage caused by the pathogen. The main objective in the extension of integrated fruit production is the reduction of the amount of applied pesticides in order to minimize adverse effects on the environment and consumers. To develop successful alternatives to the chemical plant protection a detailed knowledge about the host-pathogen-interaction is required. In the interaction of the host plant apple and the powdery mildew pathogen much research has been carried out on the plant side. Within the framework of an EU-funded project the apple powdery mildew pathogen has now been characterised by molecular analyses and in pathogenicity tests. The objective was to determine the variability between mildew samples of European and Asian origin. The results show a high level of variability regarding the pathogenicity of the tested isolates. On the molecular level it was possible to distinguish between two separate major groups of isolates. The relevance of these results for apple breeding is discussed.     

新疆泽普县小麦白粉病流行的时间动态及预测模型

2012年-2019年对泽普县春季小麦白粉病田间发生情况进行了系统调查, 并对数据进行了分析和模型拟合, 明确了当地白粉病春季发生和流行的特点?其病害春季流行曲线为典型的单峰S形曲线, 符合Logistic或Gompertz模型?在此基础上, 通过Pearson相关系数法分析了多年来该地小麦不同生育期白粉病病情指数与66个主要气象因子之间的相关关系, 筛选出影响小麦白粉病发生流行的关键气象因子为1月下旬平均日照时间?2月下旬平均气温?1月上旬-3月上旬平均气温和10月下旬-4月中旬平均日照时间, 并采用多元回归分析法建立了基于关键气象因子的小麦扬花期?灌浆初期和灌浆中期的病害预测模型?此研究结果可为当地小麦白粉病的防控提供技术支撑?     

The effect of powdery mildew (Erysiphe graminis f. sp. hordei) and leaf rust (Puccinia hordei) on spring barley in New Zealand. II. Apical development and yield potential

Reduced yields caused by powdery mildew and leaf rust in two seasons were associated with reduced plant growth. Combinations of early, late and full epidemics in one season, and 12 epidemic combinations in the second, were designed to identify crop sensitivity to disease by comparing growth and development with healthy plants. Early epidemics reduced ear number by increasing tiller death, and reduced grain number by effects on spikelet, floret or grain abortion, depending on the type of epidemic. Epidemics later in crop growth increased floret and grain abortion and also reduced grain weight.
There was no compensation by later-determined components for reduced growth and delayed development at earlier growth stages. Plants infected at early growth stages were more sensitive to late infections, seen as effects on the later-determined components, than plants which were healthy initially. Interactions occurred between epidemics at different times and are likely to occur between diseases and other constraints.     

小麦白粉菌分生孢子离体后存活时间与温度的定量关系研究

<正>小麦白粉病是我国小麦生产上的重要病害之一,由专性寄生真菌Blumeria graminis f.sp.tritici引起。此病害是典型的气传病害,病菌分生孢子可借助高空气流远距离传播为害~([1]),高空传播距离与病菌的分生孢子存活时间有直接关系,而温度是     

烯丙异噻唑对水稻叶片中NAA、ABA含量的影响与稻瘟病抗性的关系

经过１０余年小麦白粉病综合治理系统研究,摸清了东北春麦区小麦白粉病初菌源来源及侵染循环规律,建立了准确度达８６％以上的预测小麦白粉病发生与流行的预测式,明确了东北春麦区小麦白粉病菌的小种种群构成及毒力频率。