scholarly journals Fluctuations in Number of Cercospora beticola Conidia in Relationship to Environment and Disease Severity in Sugar Beet

2009 ◽  
Vol 99 (7) ◽  
pp. 796-801 ◽  
Author(s):  
J. Khan ◽  
A. Qi ◽  
M. F. R. Khan
Keyword(s):  
Relative Humidity ◽  
Sugar Beet ◽  
North Dakota ◽  
Disease Severity ◽  
Leaf Spot ◽  
Forecasting Model ◽  
Cercospora Beticola ◽  
Disease Forecasting ◽  
Cercospora Leaf Spot ◽  
Average Temperature

Cercospora leaf spot, caused by Cercospora beticola, is the most damaging foliar disease of sugar beet in Minnesota (MN) and North Dakota (ND). Research was conducted to characterize the temporal progression of aerial concentration of C. beticola conidia in association with the environment and disease severity in sugar beet. In 2003 and 2004, volumetric spore traps were placed within inoculated sugar beet plots to determine daily dispersal of conidia at Breckenridge, MN, and St. Thomas, ND. Plots were rated weekly for disease severity. At both locations, conidia were first collected in early July 2003 and late June in 2004. Peaks of conidia per cubic meter of air were observed with maxima in late August 2003 and in early September 2004 at both locations. Peaks of airborne conidium concentration were significantly correlated with the average temperature of daily hours when relative humidity was greater than 87%. Weekly mean hourly conidia per cubic meter of air was significantly (P < 0.01) associated with disease severity during both years and across locations. This study showed that C. beticola conidial numbers may be used to estimate potential disease severity that, with further research, could be incorporated in a disease forecasting model to rationalize Cercospora leaf spot management.

scholarly journals Improving the Cercospora Leaf Spot Management Model for Sugar Beet in Minnesota and North Dakota

Plant Disease ◽  
2007 ◽  
Vol 91 (9) ◽  
pp. 1105-1108 ◽  
Author(s):  
J. Khan ◽  
L. E. del Río ◽  
R. Nelson ◽  
M. F. R. Khan
Keyword(s):  
Sugar Beet ◽  
North Dakota ◽  
Disease Severity ◽  
Leaf Spot ◽  
Management Model ◽  
Initial Symptom ◽  
Cercospora Leaf Spot ◽  
Progress Curve ◽  
Management Recommendations ◽  
The Impact

Management of Cercospora leaf spot, caused by Cercospora beticola, is necessary for the economic production of sugar beet (Beta vulgaris). The objectives of this study were to evaluate the impact of two relative humidity thresholds (87 and 90%) on the daily infection values (DIVs) used to determine when fungicide applications were required, to determine whether current Cercospora management recommendations for northern areas of Minnesota and North Dakota could be used by growers in the southern areas of these states, and to compare the utility of calendar-based fungicide applications with the Cercospora management model. Research was conducted in Breckenridge, MN and St. Thomas, ND in 2003 and 2004. Fungicide applications significantly (P = 0.05) reduced maximum disease severity (ymax) and area under the disease progress curve (AUDPC) when compared with the nontreated control at both locations during 2003 and 2004. Fungicides applied according to DIVs calculated at RH ≥ 87% or RH > 90% gave similar results. The mandatory second fungicide application 14 days after the first application for southern areas did not significantly decrease disease severity or AUDPC, or improve root yield or recoverable sucrose compared with treatments without the mandatory application. This research illustrates that a DIV calculated at RH ≥ 87% would result in similar timing of fungicide applications compared with DIVs calculated at RH > 90%. The results further show that the recommendation of fungicide applications at initial symptom and subsequent applications based on DIV and disease severity should be used for both northern and southern growers. Finally, this research showed that fungicide applications based on the Cercospora management model provided similar, effective disease control with fewer fungicide applications compared with calendar-based applications.

scholarly journals First Report of the Perfect Stage of Powdery Mildew of Sugar Beet in North Dakota Caused by Erysiphe polygoni

Plant Disease ◽  
2007 ◽  
Vol 91 (4) ◽  
pp. 470-470 ◽  
Author(s):  
C. A. Bradley ◽  
P. Burlakoti ◽  
R. S. Nelson ◽  
M. F. R. Khan
Keyword(s):  
Powdery Mildew ◽  
Sugar Beet ◽  
North Dakota ◽  
Leaf Spot ◽  
Genetic Recombination ◽  
The State ◽  
Cercospora Leaf Spot ◽  
First Report ◽  
Perfect Stage ◽  
Erysiphe Polygoni

Powdery mildew caused by Erysiphe polygoni was widespread on sugar beet (Beta vulgaris) in North Dakota during 2006. This disease is generally not prevalent in the state because of the application of fungicides, which also have efficacy against powdery mildew, for control of Cercospora leaf spot caused by Cercospora beticola. Because Cercospora leaf spot pressure was low in 2006, fewer fungicide applications were made in the state, thus allowing for more observations of powdery mildew. Leaf samples from four fields near Amenia, Minto, Prosper, and St. Thomas, ND were collected in mid-September to look for the perfect stage of E. polygoni, since this has recently been observed in Idaho, Colorado, Montana, and Nebraska (1–3). Only the leaves collected from the field near Amenia had visible immature (yellow and brown) globose ascomata; ascomata were not observed on the leaves collected in the other fields. Additional leaves were collected from the field near Amenia in early October; these leaves had immature and mature (black) globose ascomata that were 70 to 105 μm in diameter. Mature ascomata contained ovoid to elliptic asci with one to four hyaline-to-golden pigmented ascospores (20 to 25 × 12 to 20 μm). The color, shape, and size of ascomata, asci, and ascospores were similar to previously reported observations (1–4). The prevalence of the perfect stage in North Dakota is unknown, since no statewide surveys were conducted. To our knowledge, this is the first report of the perfect stage of E. polygoni on sugar beet in North Dakota. The occurrence of the perfect stage could lead to a means for overwintering in this area. Because of the means for genetic recombination, the risk of fungicide resistance and the development of races may increase. References: (1) J. J. Gallian and L. E. Hanson. Plant Dis. 87:200, 2003. (2) R. M. Harveson. Plant Dis. 88:1049, 2004. (3) B. Jacobsen et al. Plant Dis. 89:1362, 2005. (4) E. G. Ruppel. Powdery mildew. Pages 13–15 in: Compendium of Beet Diseases and Insects. E. D. Whitney and J. E. Duffus, eds. The American Phytopathological Society. St. Paul, MN, 1986.

Seed-Borne Cercospora beticola can Initiate Cercospora Leaf Spot from Sugar Beet (Beta vulgaris L.) Fruit Tissue

2021 ◽  
Author(s):  
Rebecca Spanner ◽  
Jonathan Neubauer ◽  
Thies M. Heick ◽  
Michael Grusak ◽  
Olivia Hamilton ◽  
...  
Keyword(s):  
Sugar Beet ◽  
Beta Vulgaris ◽  
Leaf Spot ◽  
Xylem Sap ◽  
Cercospora Beticola ◽  
Cercospora Leaf Spot ◽  
Internal Transcribed Spacer Region ◽  
Long Distance ◽  
True Seed ◽  
Commercial Sugar

Cercospora leaf spot (CLS) is a globally important disease of sugar beet (Beta vulgaris L.) caused by the fungus Cercospora beticola. Long-distance movement of C. beticola has been indirectly evidenced in recent population genetic studies, suggesting potential dispersal via seed. Commercial sugar beet “seed” consists of the reproductive fruit (true seed surrounded by maternal pericarp tissue) coated in artificial pellet material. In this study, we confirmed the presence of viable C. beticola in sugar beet fruit for 10 of 37 tested seed lots. All isolates harbored the G143A mutation associated with quinone outside inhibitor resistance and 32 of 38 isolates had reduced demethylation inhibitor sensitivity (EC50 > 1 µg/ml). Planting of commercial sugar beet seed demonstrated the ability of seed-borne inoculum to initiate CLS in sugar beet. Cercospora beticola DNA was detected in DNA isolated from xylem sap, suggesting the vascular system is used to systemically colonize the host. We established nuclear ribosomal internal transcribed spacer region amplicon sequencing using the MinION platform to detect fungi in sugar beet fruit. Fungi from 19 different genera were identified from 11 different sugar beet seed lots, but Fusarium, Alternaria, and Cercospora were consistently the three most dominant taxa, comprising an average of 93% relative read abundance over 11 seed lots. We also present evidence that C. beticola resides in the pericarp of sugar beet fruit, rather than the true seed. The presence of seed-borne inoculum should be considered when implementing integrated disease management strategies for CLS of sugar beet in the future.

scholarly journals Monitoring Fungicide Sensitivity of Cercospora beticola of Sugar Beet for Disease Management Decisions

Plant Disease ◽  
2010 ◽  
Vol 94 (11) ◽  
pp. 1272-1282 ◽  
Author(s):  
Gary A. Secor ◽  
Viviana V. Rivera ◽  
M. F. R. Khan ◽  
Neil C. Gudmestad
Keyword(s):  
United States ◽  
Disease Management ◽  
Sugar Beet ◽  
Leaf Spot ◽  
Fungicide Resistance ◽  
The United States ◽  
Economic Damage ◽  
Cercospora Beticola ◽  
Cercospora Leaf Spot ◽  
Cooperative Effort

Cercospora leaf spot, caused by the fungus Cercospora beticola Sacc., is the most serious and important foliar disease of sugar beet (Beta vulgaris L.) wherever it is grown worldwide. Cercospora leaf spot first caused economic damage in North Dakota and Minnesota in 1980, and the disease is now endemic. This is the largest production area for sugar beet in the United States, producing 5.5 to 6.0 million metric tons on approximately 300,000 ha, which is 56% of the sugar beet production in the United States. This Plant Disease feature article details a cooperative effort among the participants in the sugar beet industry in this growing area and represents a successful collaboration and team effort to confront and change a fungicide resistance crisis to a fungicide success program. As a case study of success for managing fungicide resistance, it will serve as an example to other pathogen–fungicide systems and provide inspiration and ideas for long-term disease management by fungicides.

scholarly journals Comparison of Visual and Multispectral Radiometric Disease Evaluations of Cercospora Leaf Spot of Sugar Beet

Plant Disease ◽  
2005 ◽  
Vol 89 (2) ◽  
pp. 153-158 ◽  
Author(s):  
K. Steddom ◽  
M. W. Bredehoeft ◽  
M. Khan ◽  
C. M. Rush
Keyword(s):  
Sugar Beet ◽  
Disease Severity ◽  
Leaf Spot ◽  
Near Infrared ◽  
Potential Bias ◽  
Cercospora Leaf Spot ◽  
Industry Standard ◽  
Vegetative Indices ◽  
The Individual ◽  
Visual Assessments

Visual assessments of disease severity are currently the industry standard for quantification of the necrosis caused by Cercospora beticola on sugar beet (Beta vulgaris) leaves. We compared the precision, reproducibility, and sensitivity of a multispectral radiometer to visual disease assessments. Individual wavebands from the radiometer, as well as vegetative indices calculated from the individual wavebands, were compared with visual disease estimates from two raters at each of two research sites. Visual assessments and radiometric measurements were partially repeated immediately after the first assessment at each site. Precision, as measured by reduced coefficients of variation, was improved for all vegetative indices and individual waveband radiometric measures compared with visual assessments. Visual assessments, near-infrared singlewaveband reflectance values, and four of the six vegetative indices had high treatment F values, suggesting greater sensitivity at discriminating disease severity levels. Reproducibility, as measured by a test-retest method, was high for visual assessments, single-waveband reflectance at 810 nm, and several of the vegetative indices. The use of radiometric methods has the potential to increase the precision of assessments of Cercospora leaf spot foliar symptoms of sugar beet while eliminating potential bias. We recommend this method be used in conjunction with visual disease assessments to improve precision of assessments and guard against potential bias in evaluations.

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