An Epidemic of Downy Mildew caused by Peronospora destructor on Vidalia Sweet Onions in Georgia in 2012

2013 ◽  
Vol 14 (1) ◽  
pp. 54
Author(s):  
Venkatesan Parkunan ◽  
Ronald D. Gitaitis ◽  
Bhabesh Dutta ◽  
David B. Langston ◽  
Pingsheng Ji
Keyword(s):  
Downy Mildew ◽  
Peronospora Destructor ◽  
Recent Outbreak ◽  
The Impact ◽  
Onion Downy Mildew

The first reported occurrence of onion downy mildew (ODM) on Vidalia sweet onions in Georgia was in 1999. Although the disease is not common every year, two epidemics have occurred since 1999. The authors report here on the impact of a recent outbreak of ODM on the $100-million Vidalia onion crop in 2012. Accepted for publication 29 January 2013. Published 28 March 2013.

Control of onion downy mildew in the presence of phenylamide-resistant strains of Peronospora destructor (Berk.) Caspary

1992 ◽  
Vol 32 (5) ◽  
pp. 669 ◽  
Author(s):  
RG O'Brien
Keyword(s):  
Downy Mildew ◽  
Disease Severity ◽  
Field Trials ◽  
Copper Hydroxide ◽  
Peronospora Destructor ◽  
Phenylamide Fungicides ◽  
Resistant Strains ◽  
Onion Downy Mildew ◽  
Reduce Disease Severity

Two isolates of Peronospora destructor differed in their sensitivities to phenylamide fungicides. An isolate (3014) from the Lockyer Valley did not respond to increasing concentrations of metalaxyl, benalaxyl and oxadixyl between 0.1 and 200 mg a.i./L. An isolate (2967) from Bundaberg was sensitive to these fungicides, with EC50 values (concentrations which reduce disease severity by 50%) of 1.6, 6.0 and 12.1 mg a.i./L, respectively. Isolates 3014 and 2967 were both sensitive to dimethomorph, with EC50 values of 4.3 and 1.4 mg a.i./L, respectively. Field trials compared the efficacy of fungicides for the control of onion downy mildew in the Lockyer Valley in 1989 and 1990. In both trials, treatments containing mancozeb gave the best control, resulting in yield increases of 60% in 1990. There was no difference from the check treatment in either disease severity or yield when metalaxyl was applied, suggesting that phenylamide-resistant strains were prevalent. Other fungicide treatments which did not significantly reduce the severity of downy mildew in the 1990 trial included copper hydroxide, chlorothalonil, fosetyl-Al, and propamocarb. The experimental compound dimethomorph, although less effective than mancozeb, significantly reduced disease severity and increased yield by 24%.

scholarly journals Factors Influencing the Occurrence of Onion Downy Mildew (Peronospora destructor) Epidemics: Trends from 31 Years of Observational Data

Agronomy ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 738 ◽  
Author(s):  
Hervé Van der Heyden ◽  
Pierre Dutilleul ◽  
Jean-Benoît Charron ◽  
Guillaume J. Bilodeau ◽  
Odile Carisse
Keyword(s):  
Downy Mildew ◽  
Observational Data ◽  
Disease Incidence ◽  
Principal Component ◽  
Precipitation Regime ◽  
Peronospora Destructor ◽  
Northern Latitudes ◽  
Regional Basis ◽  
Regional Disease ◽  
Onion Downy Mildew

Onion downy mildew (ODM) caused by Peronospora destructor has been increasing annually in south-western Québec since the early 2000s, reaching 33% of affected onion fields in 2014. Using observational data collected over a period of 31 consecutive years, this study aimed to investigate the variations in ODM incidence and epidemic onset and identify the meteorological variables that influence its polyetic development. A logistic model was fitted to each ODM epidemic to estimate and compare the onset of epidemics on a regional basis. Results of this analysis showed that the first observation date, 10% epidemic onset (b10) and mid-time (b) were, on average, 30.4, 15.1 and 11.3 days earlier in 2007–2017 than in 1987–1996. Results of a principal component analysis suggested that regional disease incidence was mostly influenced by the precipitation regime, the final regional disease incidence the previous year, and warmer temperature during the harvest period the previous fall. Subsequently, the data were divided in three periods of 10, 10 and 11 years, and a discriminant analysis was performed to classify each year in the correct period. Using a sufficient subset of five discriminating variables (temperature and rainfall at harvest the previous fall, winter coldness, solar radiation, and disease incidence the previous year), it was possible to classify 93.5% of the ODM epidemics in the period where they belong. These results suggest that P. destructor may overwinter under northern latitudes and help to highlight the need for more research on overwintering and for the development of molecular-based tools enabling the monitoring of initial and secondary inoculum.

Peronospora destructor. [Descriptions of Fungi and Bacteria].

1975 ◽  
Author(s):  
K. G. Mukerji
Keyword(s):  
South Africa ◽  
New Zealand ◽  
East Asia ◽  
Downy Mildew ◽  
Geographical Distribution ◽  
Wild Species ◽  
Peronospora Destructor ◽  
North East

Abstract A description is provided for Peronospora destructor. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Affects species of Allium; common on A. cepa, rarer on A. ascalonicum, A. fistulosum, A. porrum, A. sativum, A. schoenoprasum, and a few wild species. DISEASE: Downy mildew (mildiou, falscher Mehitau) of onion. GEOGRAPHICAL DISTRIBUTION: On onion in all parts of Europe and America; north, east and south Africa, west, south and east Asia, Australia, New Zealand; and Tasmania. On other Allium crops in a few countries in Europe and on other continents (CMI Map 76. ed. 3, 1969).

scholarly journals Toward a Weather-Based Forecasting System for Fire Blight and Downy Mildew

Atmosphere ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 484 ◽  
Author(s):  
Ana Firanj Sremac ◽  
Branislava Lalić ◽  
Milena Marčić ◽  
Ljiljana Dekić
Keyword(s):  
Downy Mildew ◽  
Fire Blight ◽  
Meteorological Data ◽  
Weather Prediction ◽  
Weather Forecast ◽  
Atmospheric Model ◽  
Plasmopara Viticola ◽  
Forecasting System ◽  
Nwp Model ◽  
The Impact

The aim of this research is to present a weather-based forecasting system for apple fire blight (Erwinia amylovora) and downy mildew of grapevine (Plasmopara viticola) under Serbian agroecological conditions and test its efficacy. The weather-based forecasting system contains Numerical Weather Prediction (NWP) model outputs and a disease occurrence model. The weather forecast used is a product of the high-resolution forecast (HRES) atmospheric model by the European Centre for Medium-Range Weather Forecasts (ECMWF). For disease modelling, we selected a biometeorological system for messages on the occurrence of diseases in fruits and vines (BAHUS) because it contains both diseases with well-known and tested algorithms. Several comparisons were made: (1) forecasted variables for the fifth day are compared against measurements from the agrometeorological network at seven locations for three months (March, April, and May) in the period 2012–2018 to determine forecast efficacy; (2) BAHUS runs driven with observed and forecast meteorology were compared to test the impact of forecasted meteorological data; and (3) BAHUS runs were compared with field disease observations to estimate system efficacy in plant disease forecasts. The BAHUS runs with forecasted and observed meteorology were in good agreement. The results obtained encourage further development, with the goal of fully utilizing this weather-based forecasting system.

scholarly journals Transcriptional regulation of stilbene synthases in grapevine germplasm differentially susceptible to downy mildew

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Mario Ciaffi ◽  
Anna Rita Paolacci ◽  
Marco Paolocci ◽  
Enrica Alicandri ◽  
Valentina Bigini ◽  
...  
Keyword(s):  
Transcriptional Regulation ◽  
Downy Mildew ◽  
Transcriptional Activation ◽  
Constitutive Expression ◽  
Stilbene Synthase ◽  
Disease Symptoms ◽  
Adaptive Resistance ◽  
Genes Encoding ◽  
The Impact ◽  
Stilbene Biosynthesis

Abstract Background To limit the impact of the downy mildew disease of grapevine and reduce the need to recur to chemical treatments, an effective strategy might be recovering adaptive resistance traits in both cultivated and wild V. vinifera germplasm. Considering that stilbenes represent the most important class of phytoalexins in the Vitaceae, the constitutive expression and transcriptional activation of all the functional members of the stilbene synthase gene family were analysed in a group of nine grapevine genotypes following artificial infection with the oomycete Plasmopara viticola, the causal agent of the disease. In addition, in the same genotypes we analyzed the expression of genes encoding for two transcription factors involved in the transcriptional regulation of the stilbene synthase genes, namely VvMYB14 and VvMYB15, and of genes encoding for chalcone synthases. Results Downy mildew incidence and severity ranged from nihil to high in the grapevine genotypes considered, being low to moderate in a subgroup of V. vinifera genotypes. The constitutive expression of the stilbene synthase genes as well as the extent of their transcriptional activation following P. viticola inoculation appeared to be inversely related to the proneness to develop disease symptoms upon infection. In a specular manner, following P. viticola inoculation all the chalcone synthase genes were up-regulated in the susceptible grapevine genotypes and down-regulated in the resistant ones. The infection brought by P. viticola appeared to elicit a co-ordinated and sequential transcriptional activation of distinct stilbene synthase genes subsets, each of which may be regulated by a distinct and specific MYB transcription factor. Conclusions The present results suggest that the induction of stilbene biosynthesis may contribute to the basal immunity against the downy mildew of grapevine, thus representing an adaptive resistance trait to recover, in both cultivated and wild V. vinifera germplasm. During the early stages of P. viticola infection, an antagonistic interaction between flavonol and stilbene biosynthesis might occur, whose outcome might determine the subsequent extent of disease symptoms. Further studies are needed to decipher the possible regulatory mechanisms involved in the antagonistic crosstalk between these two metabolic pathways in resistant and susceptible genotypes in response to P. viticola.

scholarly journals Proximity to people with COVID-19 and anxiety among community residents during the epidemic in Guangzhou, China

BJPsych Open ◽  
2020 ◽  
Vol 6 (4) ◽  
Author(s):  
Jinghua Su ◽  
Xiyuan Chen ◽  
Ning Yang ◽  
Meng Sun ◽  
Liang Zhou
Keyword(s):  
Online Survey ◽  
Generalized Anxiety ◽  
Psychological Consequences ◽  
Community Residents ◽  
Recent Outbreak ◽  
Anxiety Levels ◽  
Novel Coronavirus ◽  
The Impact ◽  
Source Of Information ◽  
Insight Into

Summary The recent outbreak of a novel coronavirus pneumonia (COVID-19) may have acute psychological consequences, both in relation to the impact of the virus itself and the restrictions imposed to tackle its spread. We conducted an online survey of 403 residents in Guangzhou, China. We found the prevalence of anxiety (defined as Generalized Anxiety Disorder–7 score ≥5) was 37.7%, and anxiety was significantly and moderately correlated with worry about COVID-19. Higher anxiety levels in community residents was associated with the presence of individuals with COVID-19 in the same building; a longer time spent each day gathering information about the virus; and choosing social media as their preferred source of information. Our findings provide an insight into the psychological support and guidance about information sources that are required in this type of public health emergency.

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