scholarly journals Hop Downy Mildew Caused by Pseudoperonospora humuli in Argentina

Plant Disease ◽  
2009 ◽  
Vol 93 (8) ◽  
pp. 839-839 ◽  
Author(s):  
B. A. Pérez ◽  
E. Martínez ◽  
F. Noetinger ◽  
E. R. Wright
Keyword(s):  
Downy Mildew ◽  
Disease Incidence ◽  
Phosphorous Acid ◽  
Systemic Infection ◽  
First Record ◽  
Early Spring ◽  
Fungicide Treatment ◽  
Rio Negro ◽  
Pseudoperonospora Humuli ◽  
Downy Mildew Disease

In Argentina, hop downy mildew disease caused by Pseudoperonospora humuli first appeared in Alto Valle of Rio Negro and Neuquen (1957), Mar del Plata (1962), and El Bolson (1963) (1). The disease occurred in the hop (Humulus lupulus L.) planting areas of El Bolson (Rio Negro) and Lago Pueblo (Chubut) in 2002 and 2003. Surveys were conducted in 30 commercial hop fields from December 2002 to March 2003 to estimate disease incidence and susceptibility of cultivars planted in these fields. Hop fields were divided into five sections and 100 plants were randomly selected and assessed for the presence of disease. Symptoms that were observed in early spring included dark brown rootstocks and primary basal spikes (stunted plants with pale and curled leaves), which are characteristic of systemic infection. Later in the season, secondary infections were characterized by dark purple-to-black lesions on leaves, flowers, cones, and lateral and terminal spikes. Plant symptoms and fungal morphological markers (dichotomously branched sporangiophores; ellipsoid and papillate sporangia) agreed with hop downy mildew disease and the fungus P. humuli. Yield loss was estimated as the reduction in yield compared with the 2001–2002 season observed from five hop growers. On December 10, 70% of the hop fields had greater than 50% disease incidence and seven fields reached 100% incidence. The reduction in cone yield varied between 20 and 34% in fields without a rootstock fungicide treatment. One field with a rootstock fungicide treatment (mefenoxam, copper oxiclorure, phosphorous acid, copper sulfate, and fosetyl-Al) and regular fungicide applications had a 30% increase in cone yield compared with 2001–2002. Systemically infected plants were recorded for hop cvs. Bullion, Cascade, CEZ, GS-19, Hallertauer Mfr., Nugget, Spalt, and Traful. Previously, Cascade was rated as a resistant cultivar to the root systemic infection (1). To our knowledge, this is the first record of a hop downy mildew outbreak in Argentina during the last 30 years. Reference: (1) L. Leskovar. El Lúpulo: Su Cultivo y Procesamiento. Hemisferio Sur. Buenos Aires, 1978.

Pseudoperonospora humuli. [Descriptions of Fungi and Bacteria].

1983 ◽  
Author(s):  
S. M. Francis
Keyword(s):  
Downy Mildew ◽  
Geographical Distribution ◽  
Systemic Infection ◽  
Humulus Lupulus ◽  
Convincing Evidence ◽  
Cone Production ◽  
Secondary Infections ◽  
Pseudoperonospora Humuli ◽  
Growing Crop ◽  
Curled Leaves

Abstract A description is provided for Pseudoperonospora humuli. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOST: Humulus lupulus. DISEASE: Downy mildew of hops. The first sign of infection, seen early in the year, is the development of spindly, stunted, shoots with pale, crowded and down-curled, leaves. These are known as 'primary basal spikes' and are shoots with a systemic infection developed from mycelium which has overwintered in the rootstock. The undersurfaces of the leaves of these shoots bear large crops of sporangia which in moist and humid conditions can soon spread the disease in the growing crop. Secondary infections may occur on leaves, growing tips, flowers and cones. On the leaves they are seen either as small discrete spots or larger, more angular, brown areas. The diseased shoots arising from secondary infections and depending upon the position of the infected bud are known as 'terminal' or 'lateral' spikes. They resemble basal spikes in appearance. Infection of the flowers can inhibit cone production. If cones do develop, and become infected, the brown spots and lesions of the fungus can make them unsaleable. GEOGRAPHICAL DISTRIBUTION: CMI Map No. 14, ed. 4, 1976, with the addition of Belorussia, Estonia, India, Kinghizia, Kazakhstan, Latvia, Lithuania, Moldavia, Ukraine and Uzebekistan. TRANSMISSION: Ware (1926) demonstrated the presence of mycelium in diseased rootstocks but its significance in the overwintering of the pathogen was not fully recognized until Coley Smith (1962) showed that the primary basal spikes which develop in spring originate from infected buds on the rootstocks. Oospores, which are often produced in abundance, were at one time thought to be responsible for infection of the shoots in spring but there is no convincing evidence to support this theory.

scholarly journals Genome Sequencing and Transcriptome Analysis of the Hop Downy Mildew Pathogen Pseudoperonospora humuli Reveal Species-Specific Genes for Molecular Detection

2019 ◽  
Vol 109 (8) ◽  
pp. 1354-1366 ◽  
Author(s):  
A. Rahman ◽  
E. Góngora-Castillo ◽  
M. J. Bowman ◽  
K. L. Childs ◽  
D. H. Gent ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Cultural Practices ◽  
Disease Risk ◽  
Systemic Infection ◽  
Primary Methods ◽  
Bioinformatics Analyses ◽  
Fungicide Application ◽  
Pseudoperonospora Humuli ◽  
Species Specific ◽  
Propagation Material

Pseudoperonospora humuli is an obligate oomycete pathogen of hop (Humulus lupulus) that causes downy mildew, an important disease in most production regions in the Northern Hemisphere. The pathogen can cause a systemic infection in hop, overwinter in the root system, and infect propagation material. Substantial yield loss may occur owing to P. humuli infection of strobiles (seed cones), shoots, and cone-bearing branches. Fungicide application and cultural practices are the primary methods to manage hop downy mildew. However, effective, sustainable, and cost-effective management of downy mildew can be improved by developing early detection systems to inform on disease risk and timely fungicide application. However, no species-specific diagnostic assays or genomic resources are available for P. humuli. The genome of the P. humuli OR502AA isolate was partially sequenced using Illumina technology and assembled with ABySS. The assembly had a minimum scaffold length of 500 bp and an N50 (median scaffold length of the assembled genome) of 19.2 kbp. A total number of 18,656 genes were identified using MAKER standard gene predictions. Additionally, transcriptome assemblies were generated using RNA-seq and Trinity for seven additional P. humuli isolates. Bioinformatics analyses of next generation sequencing reads of P. humuli and P. cubensis (a closely related sister species) identified 242 candidate species-specific P. humuli genes that could be used as diagnostic molecular markers. These candidate genes were validated using polymerase chain reaction against a diverse collection of isolates from P. humuli, P. cubensis, and other oomycetes. Overall, four diagnostic markers were found to be uniquely present in P. humuli. These candidate markers identified through comparative genomics can be used for pathogen diagnostics in propagation material, such as rhizomes and vegetative cuttings, or adapted for biosurveillance of airborne sporangia, an important source of inoculum in hop downy mildew epidemics.

scholarly journals IMPROVED DOWNY MILDEW CONTROL IN WINE GRAPES WITH VOSSEN BLUE

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 605d-605
Author(s):  
Joseph A. Fiola ◽  
Gary C. Pavlis
Keyword(s):  
Downy Mildew ◽  
Disease Incidence ◽  
Total Yield ◽  
Economic Loss ◽  
Plasmopara Viticola ◽  
Wine Grapes ◽  
Incidence Data ◽  
Average Cluster ◽  
Grape Cultivars ◽  
Downy Mildew Disease

Downy Mildew, Plasmopara viticola, causes major damage and economic loss to many wine grape cultivars grown in the Northeast. The purpose of the experiment was to test the efficacy of Vossen Blue (VB; iron pigment) in association with fungicides for the control of Downy Mildew disease of wine grapes in New Jersey. The experimental plot was a planting of `Seyval Blanc' (5th leaf). Treatments (applied via back-pack sprayer) included no fungicide (control I), full fungicide (FF) (RCE commercial recs; control II), FF + 4%VB, FF + 8%VB, 8%VB, Half Rate Fungicide (HF) + 4%VB, HF + 8%VB. There were no significant differences between treatments for total yield, average cluster weight, average berry weight, Brix %, and pH. Spectrophotometric (Hunter's Lab) analysis of foliage samples revealed that leaf samples from the VB treatments had greater green color (correlate: increased chlorophyll). Analysis of subjective (1-9) disease incidence data: FF8 significantly lower disease score that FF; FF4, HF4, HF8, and FF no difference. Compared to normal full fungicide: superior Downy Mildew control was achieved by adding VB to full fungicide; equal control was achieved with half fungicide and VB.

scholarly journals High Levels of Insensitivity to Phosphonate Fungicides in Pseudoperonospora humuli

Plant Disease ◽  
2020 ◽  
Vol 104 (5) ◽  
pp. 1400-1406 ◽  
Author(s):  
David H. Gent ◽  
Mary Block ◽  
Briana J. Claassen
Keyword(s):  
Disease Control ◽  
Downy Mildew ◽  
Plant Pathogens ◽  
Phosphorous Acid ◽  
Rate Sensitivity ◽  
Field Studies ◽  
Planting Material ◽  
Pseudoperonospora Humuli ◽  
Action Committee ◽  
Allowable Rate

Phosphonate (phosphite; HPO3−2) is fungicidal against oomycetes and certain other organisms. The Fungicide Resistance Action Committee has deemed phosphonate to be at low risk of resistance development, and reduced sensitivity to phosphonate has been reported only occasionally in plant pathogens. Reduced sensitivity to the fungicide fosetyl-Al was documented in the hop downy mildew pathogen, Pseudoperonospora humuli, in the early 2000s, but disease caused by insensitive isolates could still be managed commercially if the fungicide rate was doubled from 2.24 to 4.48 kg/ha. In this research, we document the occurrence of isolates of P. humuli in Oregon that possess even higher levels of insensitivity to fosetyl-Al and other phosphonate fungicides. The median estimated effective concentration required to reduce infection by 50% (EC50) for isolates collected from two farms reporting disease control failures was 2.7% (vol/vol) phosphonate (range = 1.6 to 164.2), which was 1.6 times (range = 0.9 to 96.0) the maximum labeled rate of the phosphonate fungicide utilized. In contrast, the median EC50 for isolates obtained from experimental plots that have received only a single application of a phosphonate fungicide was 0.6% (vol/vol) phosphonate (range = 0.11 to 2.3) or 0.3 times the maximum allowable rate. Sensitivity of isolates to a phosphorous acid fungicide, fosetyl-Al, and a plant nutrient product containing an unspecified level of phosphorous acid were linearly related. Insensitivity to the maximum allowable rate of a phosphorous acid fungicide was widespread within and among hop farms in Oregon. Among 54 isolates assayed for phosphonate insensitivity, 96% had EC50 values that exceeded the maximum allow rate of the fungicide used in the assays. Field studies conducted in 2 years further demonstrated that a phosphorous fungicide, a nutrient product containing phosphorous acid, and fosetyl-Al failed to provide commercially acceptable suppression of downy mildew when applied at the maximum allowable rates and even double these rates, whereas fungicides with different modes of action provided 91% or greater disease control. The whole of this research indicates that P. humuli has been selected to tolerate fosetyl-Al and other phosphonate fungicides at rates four times greater than those used earlier to obtain satisfactory suppression of downy mildew. This finding has implications for management of the disease not only in Oregon but also, in other production regions should insensitive isolates be introduced on infected planting material.

scholarly journals Efficacy of fungicides in management of Downy mildew disease of Cucumber (Cucumis sativus L.) under open field conditions, in Dhading district of Nepal

2020 ◽  
Vol 3 (1) ◽  
pp. 240-252
Author(s):  
Shailesh Pandit ◽  
Hira Kaji Manandhar ◽  
Krishna Hari Dhakal ◽  
Sramika Rijal ◽  
Sandesh Bhandari ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Cucumis Sativus ◽  
Open Field ◽  
Disease Incidence ◽  
Block Design ◽  
Trichoderma Viride ◽  
Field Conditions ◽  
Verticillium Lecanii ◽  
Cucumis Sativus L ◽  
Downy Mildew Disease

Downy mildew (Pseudoperonospora cubensis) is one of the most important disease of cucumber under open field conditions. Hence, the experiment was conducted to study the efficacy of fungicides in management of downy mildew disease of cucumber (Cucumis sativus L.) under open field in Chauradi-7 Dhading during spring season, 2019. Bhaktapur local variety of cucumber was used for the study. The experiment was laid out in single factor randomized complete block design with four replications. Three different bio-fungicides; Trichoderma viride + Trichoderma harzianum, Bacillus subtilis, Verticillium lecanii and one chemical fungicide; Krilaxyl (metalaxyl 8% + mancozeb 64%) were used as treatments. Normal water spray served as control. It was observed that bio-fungicides had insignificant effect in controlling the downy mildew. Pathological observation such as disease incidence percentage, severity percentage and AUDPC in bio-fungicides treated plots were not significantly different from water-sprayed control plots. Similarly, biometric attributes such as number of fruit, length and diameter of fruit, weight of fruit were also non-significant. Krilaxyl resulted significant effect in controlling downy mildew, providing maximum disease reduction (37.48%-50.72%) with lowest disease incidence (1.25-61.25%) and lowest value of AUDPC (138.7). Krilaxyl treated plots had higher number of fruit (6), longer length of fruit (17.15-18.95), higher diameter of fruit (4.16- 4.45 cm) and higher weight of fruit (677 - 759 g). Hence, chemical fungicide Krilaxyl was found better for the management of downy mildew disease in open field cucumber cultivation. Further, researches on bio-fungicides, especially of native strains are required for best result.

scholarly journals Evaluation of Oxathiapiprolin for the Management of Sunflower Downy Mildew

Plant Disease ◽  
2019 ◽  
Vol 103 (10) ◽  
pp. 2498-2504 ◽  
Author(s):  
Ryan M. Humann ◽  
Keith D. Johnson ◽  
Michael J. Wunsch ◽  
Scott M. Meyer ◽  
James G. Jordahl ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Disease Incidence ◽  
Systemic Infection ◽  
Field Trials ◽  
Effective Rate ◽  
Management Tool ◽  
Damping Off ◽  
Severe Stunting ◽  
Treated Seed ◽  
Disease Pressure

Downy mildew is a yield-limiting disease of sunflower, caused by the pathogen Plasmopara halstedii. Zoospore infection of root tissue shortly after planting results in systemic infection, causing postemergence damping off or severe stunting and head sterility. Although fungicide-applied seed treatments can be an effective management tool, the pathogen is resistant to phenylamide fungicides in many growing regions, and other available fungicides have limited efficacy. Oxathiapiprolin, the first member of the piperidinyl thiazole isoxazoline fungicides, was evaluated for efficacy on downy mildew in field trials conducted from 2011 to 2015 in North Dakota. Throughout the course of the study, the rate range was narrowed from active ingredient (a.i.) at 0.45 to 116.0 µg a.i. seed−1 to an optimal effective rate of 9.37 to 18.75 µg a.i. seed−1. Within that optimal range, the downy mildew incidence of sunflower planted with oxathiapiprolin-treated seed was significantly lower than the incidence in the nontreated sunflower in all 11 trials with disease pressure. Additionally, downy mildew incidence of sunflower planted with oxathiapiprolin-treated seed was significantly lower than sunflower planted with competitive commercially available fungicide-treated seed in 10 of those 11 trials. The use of oxathiapiprolin by sunflower growers is likely to reduce disease incidence and subsequent yield loss to downy mildew.

scholarly journals Genetic Variability for Downy Mildew Disease Incidence against Virulent Downy Mildew Isolates in Mapping Population of Pearl Millet

2017 ◽  
Vol 6 (10) ◽  
pp. 595-608
Author(s):  
Anishetti Saritha ◽  
Rakesh K. Srivastava ◽  
Chelpuri Durgaraju ◽  
Narayan Reddy ◽  
Rajan Sharma ◽  
...  
Keyword(s):  
Genetic Variability ◽  
Downy Mildew ◽  
Pearl Millet ◽  
Mapping Population ◽  
Disease Incidence ◽  
Downy Mildew Disease

scholarly journals THE EFFECTIVENESS COMBINATION OF RESISTANT VARIETIES AND METALAXIL FUNGICIDE IN CONTROLLING DOWNY MILDEW DISEASE (Peronosclerospora maydis) IN MAIZE PLANT

2019 ◽  
Vol 19 (1) ◽  
pp. 42
Author(s):  
Syahrir Pakki ◽  
Nurasiah Djaenuddin
Keyword(s):  
Downy Mildew ◽  
Seed Treatment ◽  
Disease Incidence ◽  
Susceptible Variety ◽  
Treatment Conditions ◽  
Resistant Varieties ◽  
Treatment Dose ◽  
Important Disease ◽  
Downy Mildew Disease ◽  
Plot Design

Downy mildew caused by Peronosclerospora maydis is an important disease in the centers of corn cultivation in Java. The aim of this study was to determine the effectiveness of a combination of metalaxyl fungicide and varieties that have a high sustainability of downy mildew caused by P. maydis. The study was conducted in Kediri, East Java, which is an endemic area of downy mildew caused by P. maydis. The Split Plot Design with 3 replications was used in this study. The main plots were 5 corn varieties (1) Bima-3 Bantimurung, (2) Bima-20 URI, (3) Lagaligo, (4) Bima-15 Sayang, and (5) Anoman as a susceptible check. The subplots were 5 levels of seed treatment dose with metalaxyl fungicide (0 g/kg, 2 g/kg, 3 g/kg, 5 g/kg, and 7 g/kg seeds). The combination of resistant varieties with metalaxyl at a dose level of 5 g and 7 g/kg of corn seeds was effective in controlling downy mildew caused by P. maydis. In Bima-3 varieties Bantimurung and Lagaligo showed low infection reactions of 7.7-8.1%, and 10.4–11.2% respectively. In a combination of treatment conditions of susceptible varieties (Anoman) with 2, 3, 5 and 7 g/kg seeds, disease incidence reach 100% or most of the plants die. The lower incidence was also followed by yield, ear length and weight of a 1000 seeds that higher than other treatments. The combination of the use of susceptible variety with 2 g to 7 g/kg of metallaxyl doses was not effective in controlling downy mildew caused by P. maydis.

scholarly journals New sources of sorghum resistant genotypes to downy mildew disease in Uganda

2019 ◽  
Vol 20 (11) ◽  
Author(s):  
Frank Kumi ◽  
Arfang Badji ◽  
Natasha Mwila ◽  
Thomas Odong ◽  
Mildred Ochwo-Ssemakula ◽  
...  
Keyword(s):  
Grain Yield ◽  
Downy Mildew ◽  
Seed Weight ◽  
Plant Disease ◽  
Agricultural Research ◽  
Disease Incidence ◽  
Flowering Plant ◽  
Lattice Design ◽  
Resistant Genotypes ◽  
Downy Mildew Disease

Abstract. Kumi F, Badji A, Mwila N, Odong T, Ochwo-Ssemakula M, Tusiime G, Gibson P, Biruma M, Prom KL, Cuevas HE, Agbahoungba S, Rubaihayo P. 2019. New sources of sorghum resistant genotypes to downy mildew disease in Uganda. Biodiversitas 20: 3391-3397.  Sorghum downy mildew (SDM) disease is still prevalent in Uganda at varying levels of incidence and severity. In this study, a total of 100 sorghum genotypes, five (5) from (U.SA, India, and Sudan) and 95 genotypes from Uganda were evaluated for resistance to downy mildew and other agronomic traits during the second growing season of 2016 (August-December). The experiment was conducted in two locations at Makerere University Agricultural Research Institute at Kabanyolo (MUARIK) and Abi-Zonal Agricultural Research and Development Institute (Abi-ZARDI) research station at Arua. The experimental design used was 10 x 10 alpha lattice design with three replicates. Data were collected on plant disease incidence (PDI), plant disease severity (PDS), area under disease progress curve (AUDPC), days to 50% flowering, plant height, 1000 seed weight, and grain yield. Results for analysis of variance showed highly significant differences (P < 0.001) in genotypes, location, and AUDPC, yield and yield components. Disease incidence varied significantly (P < 0.001) between locations, and Arua recorded highest disease incidence and severity of 80.6 and 2.8, respectively. Results from correlation analysis showed a highly significant (P < 0.001) positive association of downy mildew disease incidence with AUDPC (0.835) which suggests that the severity of SDM disease increased with disease incidence, whiles significant (P < 0.001) negative correlation was recorded for days to 50 % flowering (-0.302), 1000 seed weight (-0.471), and grain yield (-0.585), suggesting that grain yield and yield component decreased significantly with increase in SDM incidence and severity. Two resistant (PI 656061 and PI 533831) and four moderately resistant (E 40, MAKSO 8, PI 655990 and Epuripur) genotypes were identified from this study. These genotypes were recommended for sorghum breeding program against downy mildew disease.

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