Effects of crop management patterns on coffee rust epidemics

The effects of crop management patterns on coffee rust epidemics, caused by Hemileia vastatrix , are not well documented despite large amounts of data acquired in the field on epidemics, and much modelling work done on this disease. One main reason for this gap between epidemiological knowledge and understanding for management resides in the lack of links between many studies and actual production situations in the field. Coffee rust epidemics are based on a seemingly simple infection cycle, but develop polycyclic epidemics in a season and polyetic epidemics over successive seasons. These higher-level processes involve a very large number of environmental variables and, as in any system involving a perennial crop, the physiology of the coffee crop and how it affects crop yield. Crop management is therefore expected to have large effects on coffee rust epidemics because of its immediate effect on the infection cycle, but also because of its cumulative effect on ongoing and successive epidemics. Quantitative examples taken from a survey conducted in Honduras illustrate how crop management, different combinations of shade, coffee tree density, fertilization and pruning may strongly influence coffee rust epidemics through effects on microclimate and plant physiology which, in turn, influence the life cycle of the fungus. We suggest there is a need for novel coffee rust management systems which fully integrate crop management patterns in order to manage the disease in a sustainable way.     

Nanoparticles in the management of brown eye spot in coffee

European Journal of Plant Pathology - Brown eye spot (Cercospora coffeicola) is one of the main diseases of coffee (Coffea arabica L.) and represents a serious phytosanitary problem for the crop....     

Factors affecting the onset of cercospora leaf spot epidemics in sugar beet and establishment of disease-monitoring thresholds

ABSTRACT Severe Cercospora leaf spots epidemics in sugar beet during the late 1980s and early 1990s in southern Germany prompted us to initiate investigations on the epidemiology of the causal agent, Cercospora beticola. The data set involved 69 field trials (1993 to 2003) focusing on factors affecting the epidemic onset of this disease. Observations were made at weekly intervals, recording the calendar week when canopy closure occurred (growth stage according to BBCH scale = 39) and symptom development by assessing the percentage of infected leaf area on a single-leaf basis (n = 40 plants). These monitoring trials revealed that epidemic onset varied between early July and mid-September. Hence, the target was to identify the reasons for this variation in order to deduct the most suitable approach for predicting epidemic onset. Differences in cultivar resistance explained part of epidemic onset variability, as did different timings of canopy closure, presumably due to associated microclimate changes. Moreover, meteorological variables were considered as potential reasons for variation in epidemic onset. The weather-dependent infection probability was assessed by daily infection values (DIV) in the range from 0 to 1 using hourly weather data. For calculating DIVs, the temperature effect was quantified by the proportions of the latent period (LP) relative to the optimum at 20 to 25 degrees C, established by artificial inoculation of sugar beet plants in growth cabinets. Artificial infection experiments further established that air relative humidity (RH) >95% or leaf wetness was required for infection and subsequent lesion development. Under field conditions, the probability of leaf wetness was 75% at RH >90%. Therefore, DIVs were set to 0 for RH 相似文献   

Infection process and defense response of two distinct symptoms of Cercospora leaf spot in coffee leaves

Phytoparasitica - Cercospora leaf spot, an important disease in coffee caused by the fungus Cercospora coffeicola, can appear as two distinct symptoms on leaves, which are ‘brown eye...     

棉花轮纹斑病研究进展及防控策略

棉花是重要的天然纤维作物和油料作物。棉花轮纹斑病作为一种重要的棉花叶部病害,在我国主要棉区广泛发生,严重影响棉花的产量和品质,造成重大的经济损失,限制了棉花产业的可持续发展。本文围绕棉花轮纹斑病病害症状、发生危害、病原物种类、病害循环和发病条件等进行了综述,并介绍了实际生产中防控该病害发生危害的主要策略。     

Modulation of primary and secondary infections in epidemics of carrot cavity spot through agronomic management practices

The relative importance of primary and secondary infections (auto- and alloinfections) in the development of a carrot cavity spot (CCS) epidemic caused by Pythium spp. were investigated. Three cropping factors: fungicide application, soil moisture and planting density, were selected as the key variables affecting the disease tetrahedron. Their effects on: (i) disease measurements at a specific time, (ii) the areas under the disease progress curves (AUDPCs) and (iii) a time-dependent parameter in a pathometric incidence-severity relationship, were studied. Mefenoxam applications 5 and 9 weeks after sowing reduced the intensity of a field CCS epidemic that involved both primary and secondary infections. In microcosm experiments, mefenoxam reduced secondary infections by Pythium violae obtained by transplanting infected carrot roots and slowed disease progress (1·6 lesions per root in treated versus 5·8 lesions in non-treated microcosms). A deficit of soil moisture limited the movement of Pythium propagules to host tissue, and thus reduced primary infections in the field; it also promoted the healing of lesions, limiting lesion expansion and the potential for alloinfections (6·8–7·5 lesions per root in irrigated plots compared with 2·4 lesions in non-irrigated plots). A negative relationship between the mean root-to-root distance and the rate of alloinfections was established in microcosms; a reduction in mean planting density was also effective in limiting CCS development (0·5, 1·6 and 2·0 lesions per root in microcosms containing 8, 16 and 31 roots, respectively). An integrated disease management system based on a combination of cultural methods, such as optimized fungicide application, date of harvest versus soil moisture content, and host density versus planting pattern, may make a useful contribute to the control of CCS.     

Cultivar mixtures for the simultaneous management of multiple diseases: tan spot and leaf rust of wheat

ABSTRACT Because of differences in life histories between Puccinia triticina, a highly specialized, polycyclic, windborne pathogen with a shallow dispersal gradient, and Pyrenophora tritici-repentis, a residue-borne pathogen with a steep dispersal gradient, wheat mixtures are expected to be more effective at controlling leaf rust than tan spot. The objectives of this research were to determine the effect of two-cultivar mixtures with varying proportions and different pathogen resistance profiles on the severity of tan spot and leaf rust, to evaluate yield of the mixtures in the presence or absence of disease, and to directly compare the relative effectiveness of cultivar mixing for tan spot versus leaf rust. In a field experiment at two sites in Kansas over two growing seasons, winter wheat cvs. Jagger and 2145, which have differential resistance reactions to leaf rust and tan spot, each were planted in proportions of 0.25, 0.50, 0.75, and 1.00. Plots were inoculated with each pathogen alone, both pathogens, treated with a fungicide, or exposed to ambient conditions. For both diseases for all siteyears, severity decreased substantially on the susceptible cultivar as the proportion of that cultivar decreased in mixture. Mixtures were significantly more effective at reducing leaf rust than tan spot in three of four site-years. Mixtures generally yielded the same as the weighted mean of components in monoculture although, in two of three site-years, at least one fungicide-treated and one diseased mixture each yielded higher than expected values. Although this particular mixture produced only modest yield benefits, the potential for simultaneous reductions in tan spot and leaf rust was demonstrated.     

甘草叶斑病的发生与病原菌鉴定

近年来,在甘肃省兰州市及渭源地区甘草产区发现一种甘草新病害—甘草叶斑病。2006－2008年对其发病情况进行了调查,甘草叶斑病在6月下旬开始发病,9月中旬为发病高峰期,发病率达80%。高燥地发病率低于低洼地,采用轮作可减轻甘草叶斑病的发生。经过对甘草叶斑病病原菌形态、培养性状和致病性等方面的测定表明,病原菌为豆链格孢（Alternaria azukiae）。通过寄主范围测定表明,该病原菌亦可侵染独活、羌活等药用植物。对大黄、苍耳等不具侵染性。     

Comparative analyses of spot blotch and tan spot epidemics on wheat under optimum and late sowing period in South Asia

In South Asia, foliar blight of wheat (Triticum aestivum L.) is a disease complex caused by Cochliobolus sativus (the spot blotch pathogen) and Pyrenophora tritici-repentis (the tan spot pathogen) which can reduce yields by >30?%. Little is known about the effects of wheat genotypes and their planting time on foliar blight epidemics. Field experiments were conducted to determine the infection potential and epidemic development of C. sativus and P. tritici-repentis on two susceptible (Sonalika and BL1473) and two tolerant (NL750 and Milan/Shanghai-7) wheat genotypes under optimum (November 26) and late (December 11 and December 26) planting conditions. The dynamics of airborne conidia were studied using air samplers. The highest aerial concentrations of conidia and disease incidence of both pathogens on all four wheat genotypes were detected during the first 3?weeks of March under both optimum and late seeding conditions in both years. Compared to optimum sowing time (i.e. November 26), wheat genotypes had higher disease severity when planted late on December 11 and 26. The disease complex reduced grain yield by 20.5, 27.2 and 37.3?% for November 26, December 11 and December 26 plantings, respectively in 2004. The corresponding differences were 17.7, 23.6 and 30.2?% in 2005. The findings of this study provide valuable information on the epidemiology of spot blotch and tan spot, which could help in developing strategies for managing these diseases in South Asian region through the selection of suitable genotypes and planting dates.     

Influence of crop management on take-all development and disease cycles on winter wheat

ABSTRACT Wheat was assessed at four crop growth stages for take-all (Gaeumannomyces graminis var. tritici) in a series of field trials that studied the effects of five wheat management practices: sowing date, plant density, nitrogen fertilizer dose and form, and removal/burial of cereal straw. An equation expressing disease level as a function of degree days was fitted to the observed disease levels. This equation was based on take-all epidemiology and depended on two parameters reflecting the importance of the primary and secondary infection cycles, respectively. Early sowing always increased disease frequency via primary infection cycle; its influence on the secondary cycle was variable. Primary infection and earliness of disease onset were increased by high density; however, at mid-season take-all was positively correlated to the root number per plant, which was itself negatively correlated to plant density. At late stages of development, neither plant density nor root number per plant had any influence on disease. A high nitrogen dose increased both take-all on seminal roots and severity of primary infection cycle but decreased take-all on nodal roots and secondary infection cycle. Ammonium (versus ammonium nitrate) fertilizer always decreased disease levels and infection cycles, whereas straw treatment (burial versus removal of straw from the previous cereal crop) had no influence.     

Influence of crop management on eyespot development and infection cycles of winter wheat

Wheat was assessed at four crop growth stages for eyespot (anamorph Pseudocercosporella herpotrichoides, teleomorph Tapesia yallundae) in a series of field trials that studied the effects on disease frequency of five wheat management techniques (sowing date and density, nitrogen fertiliser dose and form, removal/burial of cereal straw). An equation expressing disease level as a function of degree-days was fitted to the observed disease levels. This equation was based on eyespot epidemiology and depended on two parameters illustrating the importance of the primary and the secondary infection cycles respectively. Cultural practices were classified according to the importance of their effects on disease, and these effects could be related to infection cycles and host plant architecture. Sowing date had the earliest and strongest effect; early sowing always increased disease frequency through the primary infection cycle, and its influence on the secondary cycle was variable. Disease frequency was increased by high plant density and/or a low shoot number per plant through primary infection; the secondary cycle was, however, decreased by a low shoot number per plant, which reduced late disease development at high plant density. High nitrogen doses increased disease levels and the severity of both infection cycles, but this effect was partly hidden by a simultaneous stimulation of tillering and thus an indirect decrease of disease incidence. When significant, ammonium (vs ammonium nitrate) fertiliser decreased eyespot levels and infection cycles whereas straw treatment (burial vs removal of straw from the previous cereal crop) had no effect.     

三类杀菌剂对牡丹腔孢叶斑病菌生长和发育的影响

腔孢叶斑病是牡丹生产上出现的一种新病害,近几年在洛阳及菏泽牡丹种植园危害越来越重。为了筛选防治该病的化学药剂,本文采用菌丝生长速率法测定了3类8种杀菌剂对病菌菌丝生长的抑制活性,采用涂布平板法测定了多菌灵、戊唑醇及嘧菌酯对病菌孢子萌发和芽管伸长的影响,并在含药平板上测定了3种药剂对病菌产孢量的作用。结果表明:三唑类药剂对病菌菌丝生长的毒力最强,EC50为0.020~0.096μg/mL,且戊唑醇对孢子萌发和产孢也有很强的抑制活性,在0.1μg/mL时孢子即不能萌发;甲氧基丙烯酸酯类药剂对菌丝生长的毒力较强,EC50为0.408~0.939μg/mL,嘧菌酯对芽管伸长和产孢量均表现出很强的抑制活性,10μg/mL时,芽管几乎不再伸长,对产孢的抑制率可达到99%以上;而苯并咪唑类药剂对菌丝生长的毒力较弱,EC50为12.167~30.104μg/mL,多菌灵对孢子萌发的抑制作用弱,100μg/mL时孢子萌发率仍达到90%以上,对产孢的抑制作用也较弱,为63.02%。根据药剂对病菌生长和发育各阶段的影响,生产中应采用适宜的施用方法:戊唑醇和嘧菌酯可作为保护剂在病害发生前期喷施,也可作为治疗剂在病害发生流行期应用,但为防止抗药性菌株的出现,两者应当轮换或复配使用。     

Multiple Alternaria species groups are associated with leaf blotch and fruit spot diseases of apple in Australia

Leaf blotch and fruit spot of apple caused by Alternaria species occur in apple orchards in Australia. However, there is no information on the identity of the pathogens and whether one or more Alternaria species cause both diseases in Australia. Using DNA sequencing and morphological and cultural characteristics of 51 isolates obtained from apple leaves and fruit with symptoms in Australia, Alternaria species groups associated with leaf blotch and fruit spot of apples were identified. Sequences of Alternaria allergen a1 and endopolygalacturonase gene regions revealed that multiple Alternaria species groups are associated with both diseases. Phylogenetic analysis of concatenated sequences of the two genes resulted in four clades representing A. arborescens and A. arborescens‐like isolates in clade 1, A. tenuissima/A. mali isolates in clade 2, A. alternata/A. tenuissima intermediate isolates in clade 3 and A. longipes and A. longipes‐like isolates in clade 4. The clades formed using sequence information were supported by colony characteristics and sporulation patterns. The source of the isolates in each clade included both the leaf blotch variant and the fruit spot variant of the disease. Alternaria arborescens‐like isolates were the most prevalent (47%) and occurred in all six states of Australia, while A. alternata/A. tenuissima intermediate isolates (14%) and A. tenuissima/A. mali isolates (6%) occurred mostly in Queensland and New South Wales, respectively. Implications of multiple Alternaria species groups on apples in Australia are discussed.     

梨叶枯病发生规律与诱病因子研究

梨叶枯病 (Mycovellosiella pyricola Guo,Chen&;Zhang)是梨树新病害 ,分布于甘肃临夏、兰州、定西等地。病菌以子座在病落叶上越冬 ,翌年 6月初显症 ,8月中、下旬发病达高峰期。降雨量、湿度是主要诱病因子 ,立地条件和各种栽培措施对病害也有一定影响     

云南蓝莓叶斑病的病原菌鉴定

<正>蓝莓(Vaccinium spp.)属于杜鹃花科(Ericaceae)越橘属(Vaccinium)多年生小浆果类果树,广泛应用于医药、保健、化妆品和环境保护等领域,联合国粮农组织将其果实列为世界五大健康食品之一。我国已有10多个省份开始大面积的蓝莓商业化栽培[1],这也是南方酸性土丘陵地区值得发展的经济作物。随着栽培面积的不断扩大,蓝莓病害日趋突出,严重影响和制约蓝莓产业的发展。     

青海省樱桃叶斑病病原菌的分离与鉴定

为明确引起青海省樱桃叶斑病病原菌的种类,本研究从西宁市城北区、海东市乐都区和贵德县的樱桃上采集有叶斑症状的叶片,采用组织分离法分离出病原菌,通过观察病原菌的形态特征,结合rDNA-ITS、EF-1α和Alt a 1基因序列分析对病原菌的种类进行了鉴定,并用柯赫氏法则进行验证。结果表明,共获得279株病原菌菌株,分属链格孢Alternaria alternata、细极链格孢A.tenuissima和刺盘孢属Colletotrichum spp.,分离频率分别为84.95%、5.02%和10.03%。采用柯赫氏法则进行离体叶片致病性测定,接种叶片100%发病,说明引起青海省樱桃叶斑病的病原菌为链格孢、细极链格孢和刺盘孢属真菌,且链格孢为主要病原菌。该研究结果可为青海省樱桃叶斑病的综合防治提供理论依据。     

西瓜叶斑病病原菌的鉴定及室内药剂筛选

2022年在上海市浦东新区西瓜上发生一种深褐色、不规则至近圆形斑的叶部病害。采用组织分离法对病害样本进行分离, 分离物SHCCC01经柯赫氏法则验证具有较强致病性。根据分离物的菌落特征、分生孢子形态、生物学特征以及基于核糖体内部转录间隔区(internal transcribed spacer, ITS)、组蛋白基因(histone, His)、真核翻译延伸因子1α(translation elongation factor 1α, TEF-1α)和肌动蛋白 (actin, Act)基因联合系统发育分析等, 将病原菌鉴定为瓜类尾孢Cercospora citrullina。10种杀菌剂对该病原菌的毒力测定试验结果表明:氟啶胺、己唑醇、氟环唑、戊唑醇等4种药剂对病原菌的抑菌活性较高, 其EC50分别为0.375 2、0.575 4、1.472 3、1.890 2 μg/mL。这些结果为西瓜尾孢叶斑病的防控和杀菌剂登记提供了重要依据。