Nitrogen and Fungicide Applications for the Management of Fungal Blights of Carrot

Alternaria leaf blight (ALB) caused by Alternaria dauci (Kühn) Groves and Skolko and Cercospora leaf spot (CLS) caused by Cercospora carotae (Pass.) Solheim are the major foliar diseases of carrot in Ontario, Canada. In addition to reducing photosynthetic area, the diseases can weaken carrot tops, which can break during mechanical harvesting, reducing harvested yields. Fungicides are commonly used to manage the disease, but there is potential to reduce fungicide applications through nitrogen (N) management. Trials were conducted on mineral soils from 2006 to 2008 to determine the importance of applied N and fungicide applications to control fungal leaf blights of carrot. Three rates of N (0, 110, and 220 kg·ha−1) and 0, 3, or 5 (2006 and 2007) or 6 (2008) fungicide applications were applied. Leaf blight severity was assessed biweekly throughout the season and at harvest. The severity of both ALB and CLS and combined disease severity index at harvest decreased with increasing N and fungicide application. In some cases, disease severity of carrots treated with high N and no fungicides was equivalent to carrots treated with no N and five fungicide sprays. Total and marketable yield increased with increasing number of fungicide sprays in 2006 and 2007, but N application did not affect yield. Results suggest that severity of ALB and CLS can be minimized through a combination of N and fungicide applications, but rates of N higher than 110 kg·ha−1 may reduce marketable yield through a decrease in stand and an increase in oversized roots.

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An IPM Program for Managing Fungal Leaf Blight Diseases of Carrot in New York

Plant Disease ◽

10.1094/pd-91-0059 ◽

2007 ◽

Vol 91 (1) ◽

pp. 59-65 ◽

Cited By ~ 2

Author(s):

B. K. Gugino ◽

J. E. Carroll ◽

T. L. Widmer ◽

P. Chen ◽

G. S. Abawi

Keyword(s):

New York ◽

Disease Severity ◽

Crop Rotation ◽

Disease Incidence ◽

Leaf Blight ◽

Yield Reduction ◽

Weather Forecasts ◽

Alternaria Dauci ◽

Leaf Blights ◽

Cultivar Susceptibility

Fungal leaf blight diseases caused by Cercospora carotae and Alternaria dauci occur annually on processing carrot in New York, with growers applying up to eight fungicide sprays to manage these diseases. An integrated pest management (IPM) program involving the use of a 25% disease incidence threshold to prompt the first fungicide application and timing subsequent sprays by monitoring for increases in disease severity and weather forecasts in conjunction with a 10- to 14-day spray interval was evaluated in grower fields in 1997 and 1998. The IPM plots, compared with the grower plots, required two to six fewer fungicide applications but showed no yield reduction. From 1999 to 2004, the IPM program was validated and the effect of crop rotation and carrot cultivar susceptibility also were assessed. Carrot plants growing in fields with 2-year or longer crop rotation intervals reached the 25% disease incidence threshold later in the season and required fewer fungicide applications. The less-susceptible carrot cultivars also reached the 25% disease incidence threshold later, required fewer fungicide applications, and were less severely diseased than more susceptible cultivars. Validation of the IPM program in New York showed that both fungal leaf blights can be managed effectively using a 25% incidence threshold to prompt the first fungicide spray and making the subsequent fungicide applications based on increases in disease severity, weather forecasts, and a 10- to 14-day spray interval.

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Effect of Foliar Trimming and Fungicides on Apothecial Number of Sclerotinia sclerotiorum, Leaf Blight Severity, Yield, and Canopy Microclimate in Carrot

Plant Disease ◽

10.1094/pdis-92-1-0132 ◽

2008 ◽

Vol 92 (1) ◽

pp. 132-136 ◽

Cited By ~ 6

Author(s):

Mary Ruth McDonald ◽

Kevin D. Vander Kooi ◽

Sean M. Westerveld

Keyword(s):

Relative Humidity ◽

Sclerotinia Sclerotiorum ◽

Organic Soil ◽

Leaf Blight ◽

Research Station ◽

Marketable Yield ◽

Sclerotinia Rot ◽

Alternaria Dauci ◽

The University ◽

Cercospora Carotae

Foliar trimming of the carrot canopy has potential for reducing the severity of Sclerotinia (Sclerotinia sclerotiorum) rot of carrot (Daucus carota subsp. sativus). The effect of trimming the carrot foliage once or twice, with and without fungicide application, was examined on carrot plants grown on organic soil for 3 years at the University of Guelph–Muck Crops Research Station in Ontario, Canada. The number of S. sclerotiorum apothecia, carrot leaf blight (CLB; Alternaria dauci and Cercospora carotae) severity, canopy microclimate, and total and marketable yield were assessed. The number of apothecia of S. sclerotiorum and relative humidity in the canopy were reduced by trimming done at either the first observation of apothecia or at 100 days after seeding (DAS). In both cases, the effects of trimming on canopy microclimate lasted between 2 and 4 weeks. Trimming the canopy twice during the season did not reduce the number of apothecia compared with trimming the canopy once at 100 DAS. Foliar trimming had little effect on CLB severity. This was attributed mainly to the lower requirement of the CLB pathogens for prolonged periods of high relative humidity and leaf wetness compared with S. sclerotiorum. Foliar trimming did not improve the efficacy of fungicide applications for CLB control. Trimming the canopy once or twice had no effect on total or marketable yield. Thus, trimming has potential to improve the management of Sclerotinia rot of carrot, and trimming both at first observation of apothecia and at 100 DAS could reduce apothecia production and relative humidity within the canopy.

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Potential of Bacillus subtilis for controlling bacterial leaf blight pathogen in rice

Food Research ◽

10.26656/fr.2017.4(s5).011 ◽

2020 ◽

Vol 4 (S5) ◽

pp. 124-130

Author(s):

K.S. Ku Asmah ◽

Z. Sapak

Keyword(s):

Bacillus Subtilis ◽

Disease Severity ◽

Severe Disease ◽

Severity Index ◽

Leaf Blight ◽

Bacterial Leaf Blight ◽

In Vivo Studies ◽

Disease Severity Index ◽

Rice Plants

Bacterial leaf blight (BLB) of rice is an economically important disease caused by Xanthomonas oryzae pv. oryzae (Xoo) throughout the world. To control this disease, bacterial isolate of Bacillus subtilis UiTMB1 was screened for the antagonistic activity against the pathogen in vitro and in vivo studies. A bacterial assay and detached leaf technique were used to evaluate the potential of the bacterium against BLB pathogen in the laboratory. Meanwhile, the glasshouse study was conducted to further examine the aptitudes of the isolate on the disease control and growth-promoting of rice plants. The findings revealed that B. subtilis UiTMB1 is able to control the disease and enhance the growth of rice plants. Rice plants treated with B. subtilis UiTMB1 before being inoculated with BLB pathogen showed less severe disease symptoms with low disease severity index of 3.43 compared to rice plants without B. subtilis UiTMB1 with high disease severity index of 8.4. Besides controlling the disease, B. subtilis UiTMB1 was also promoting plant height, chlorophyll content, number of tillers and biomass of rice plants.

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Relationship Between Nitrogen Fertilization and Cercospora Leaf Spot and Alternaria Leaf Blight of Carrot

HortScience ◽

10.21273/hortsci.43.5.1522 ◽

2008 ◽

Vol 43 (5) ◽

pp. 1522-1527 ◽

Cited By ~ 5

Author(s):

Sean M. Westerveld ◽

Alan W. McKeown ◽

Mary Ruth McDonald

Keyword(s):

Leaf Spot ◽

Field Experiments ◽

Field Trials ◽

Application Rate ◽

Leaf Blight ◽

Cercospora Leaf Spot ◽

N Application ◽

Alternaria Leaf Blight ◽

N Application Rate ◽

Alternaria Dauci

Alternaria leaf blight (ALB) and Cercospora leaf spot (CLS) are economically important diseases of carrot in Ontario. Field experiments were conducted in the Holland Marsh, Ontario, to determine the effect of nitrogen (N) application rates on both diseases. Five rates of N were applied to organic and mineral soils in which two carrot cultivars, Idaho and Fontana, were grown in each of 2002, 2003, and 2004. Both diseases were rated every 2 weeks on a scale of 0 (healthy) to 10 (tops destroyed), and the number of live (green) leaves per plant was assessed at harvest. In addition, three N rates were applied to carrot plants grown in the greenhouse, and the plants were inoculated with Alternaria dauci (Kühn) Groves and Skolko. Disease severity, senescence, and sap nitrate-N concentration were assessed. In the field trials, the response of ALB and CLS to N application rate was relatively consistent across cultivar, soil type, and year. Area-under-the-disease-progress curves typically increased with decreasing N rate for both diseases. In lower N treatments, this resulted in fewer live leaves per plant at harvest. In the greenhouse, ALB severity increased with increasing amount of leaf senescence at final assessment. The results suggest that N application rate could be used to reduce the need for fungicide applications to control these diseases in the field.

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Integrating Disease Thresholds with TOM-CAST for Carrot Foliar Blight Management

Plant Disease ◽

10.1094/pdis-91-7-0798 ◽

2007 ◽

Vol 91 (7) ◽

pp. 798-804 ◽

Cited By ~ 10

Author(s):

R. S. Bounds ◽

R. H. Podolsky ◽

M. K. Hausbeck

Keyword(s):

Production Systems ◽

Integrated Management ◽

Leaf Blight ◽

Management Approach ◽

Fresh Market ◽

Cercospora Leaf Spot ◽

Disease Symptoms ◽

Foliar Blight ◽

Alternaria Dauci ◽

Disease Threshold

Cercospora carotae and Alternaria dauci cause foliar blight on carrot (Daucus carota subsp. sativus) and are managed with fungicides to prevent yield loss. Sprays are initiated prior to disease symptoms and reapplied frequently, but some of these applications may not be necessary when the threat of disease is low. Delaying the initial fungicide spray until disease symptoms are observed and applying subsequent sprays according to the TOM-CAST disease forecaster may reduce fungicide inputs. The objective of this 2-year field study was to compare preventive, calendar-based application schedules with an integrated management approach that incorporates disease scouting to initiate fungicide application and the TOM-CAST system for timing subsequent fungicide sprays to manage foliar blight on processing, fresh market, and cut-and-peel carrot cultivars in Michigan. Applications of the fungicides chlorothalonil alternated with azoxystrobin were made prior to disease symptoms (0% blight) or when the foliage became blighted at a trace, 5%, or 10% severity level. Fungicides were reapplied every 7 or 10 days or according to TOM-CAST using disease severity value (DSV) thresholds of 15, 20, or 25. Initiating fungicide treatment at a trace level of disease and timing subsequent sprays according to the TOM-CAST 15-DSV forecaster was comparable to the preventive, calendar-based fungicide regime. One to five fewer applications were needed, while fungicide costs were reduced by $21 to $141 per hectare, when spraying at the trace disease threshold and reapplying according to the TOM-CAST 15-DSV program compared with the 7- or 10-day intervals initiated at 0% blight. Fungicide programs initiated at 5 or 10% leaf blight often provided less control than programs initiated at 0% and trace disease. This study highlights the importance of initiating a fungicide program prior to advanced foliar blight and validates the TOM-CAST 15-DSV forecaster for managing Cercospora leaf spot and Alternaria leaf blight in three carrot production systems.

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Impact of commercial foliage trimming on disease suppression and yield of processing carrots in Nova Scotia, Canada

Canadian Journal of Plant Science ◽

10.4141/cjps2013-249 ◽

2013 ◽

Vol 93 (6) ◽

pp. 1155-1163

Author(s):

G. E. McIsaac ◽

K. R. Sanderson ◽

R. D. Peters ◽

D. J. Garbary ◽

S. A. E. Fillmore

Keyword(s):

Nova Scotia ◽

Prince Edward Island ◽

Disease Suppression ◽

Disease Development ◽

Marketable Yield ◽

Production Region ◽

Growing Seasons ◽

Alternaria Dauci ◽

Side Trimming ◽

Cercospora Carotae

McIsaac, G., Sanderson, K. R., Peters, R. D., Garbary, D. J. and Fillmore, S. A. E. 2013. Impact of commercial foliage trimming on disease suppression and yield of processing carrots in Nova Scotia, Canada. Can. J. Plant Sci. 93: 1155–1163. Carrot side-trimming opens the carrot canopy, permitting greater sunlight penetration and airflow. This reduces moisture build-up and creates unfavorable conditions for the development of common carrot pathogens such as Sclerotinia sclerotiorum (Lib.) de Bary. This study was carried out during the 2008 and 2009 growing seasons and was the first to examine the effects of foliage trimming on disease development in the processing carrot production region of Nova Scotia, Canada. Research focused on the effects of foliage trimming on disease suppression and yield using a commercial-sized trimmer in processing slicer carrots over consecutive growing seasons. This study was also the first to look at the effect of trimming on the suppression of Alternaria dauci (J.G. Kühn) J.W. Groves & Skolko and Cercospora carotae (Pass.), two economically important carrot pathogens causing leaf blight diseases in this region of Canada. Plots were established in commercial fields throughout Colchester County, Nova Scotia. Each field had a trimmed and an untrimmed section. All plots were assessed for disease presence at the time of trimming and again at harvest. Foliage trimming was found to have no significant (P=0.05) effect on biological and marketable yield and generated anecdotal reports of ease of crop maintenance and harvest. The severity of diseases caused by Alternaria, Cercospora and Sclerotinia varied among cultivars and significant cultivar×trimming interactions were noted in some cases. Foliage trimming is becoming standard practice in the carrot industry as several commercial carrot producers in North America have adapted the technology to suit their production needs after the prototype foliage trimmer was designed, built, and demonstrated by researchers at Agriculture and Agri-Food Canada, Charlottetown, Prince Edward Island.

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Comparing Disease Forecasters for Timing Fungicide Sprays to Control Foliar Blight on Carrot

Plant Disease ◽

10.1094/pd-90-0264 ◽

2006 ◽

Vol 90 (3) ◽

pp. 264-268 ◽

Cited By ~ 13

Author(s):

R. S. Bounds ◽

M. K. Hausbeck ◽

R. H. Podolsky

Keyword(s):

Disease Severity ◽

Environmental Conditions ◽

Disease Forecasting ◽

Foliar Blight ◽

Alternaria Dauci ◽

Health Rating ◽

Cercospora Carotae ◽

Weekly Application

Alternaria dauci and Cercospora carotae cause foliar blight on carrot and can reduce yield in severely blighted fields. Historically, fungicides are applied every 7 to 14 days even though applications may be made when environmental conditions do not favor blight development. The purpose of this study was to compare a calendar-based application schedule with three disease forecasting systems for timing fungicide sprays to limit foliar blight, and included (i) an A. dauci disease forecaster, (ii) TOM-CAST, using a threshold of 15 disease severity values, and (iii) a disease forecaster developed to control C. apii on celery. Chlorothalonil was applied weekly or according to the forecasting systems to blight-susceptible ‘Cellobunch’ carrot plants in 2001 and 2002. Overall petiole health was poor ≥8.3; 10 = 100% petiole necrosis) when fungicides were not used. Although all disease forecasters maintained petiole health (≤5.3; 1 = healthy and vigorous), the TOM-CAST program had the best petiole health rating each year (≤2.8). TOM-CAST prompted 38 to 54% fewer applications than the weekly application schedule, resulting in a fungicide savings of $105 and $147/ha in 2001 and 2002, respectively, while providing similar blight control. The number of sprays also was reduced when fungicides were applied according to the A. dauci and C. apii forecasters, but acceptable blight control was not always achieved.

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EVALUATION OF NONIONIC SURFACTANTS FOR CONTROL OF CLUBROOT OF CABBAGE USING BAREROOT AND PLUG TRANSPLANTS OF TWO CULTIVARS

HortScience ◽

10.21273/hortsci.27.6.607b ◽

1992 ◽

Vol 27 (6) ◽

pp. 607b-607

Author(s):

W. Tietjen ◽

P.J. Nitzsche ◽

W.P. Cowgill ◽

M.H. Maletta ◽

S.A. Johnston

Keyword(s):

Brassica Oleracea ◽

Disease Severity ◽

Nonionic Surfactants ◽

Plasmodiophora Brassicae ◽

Severity Index ◽

Effective Control ◽

Disease Severity Index

`Market Prize' and `Bravo' cabbage (Brassica oleracea Var. capitata L.), transplanted as peat plug and bareroot plants into a field naturally infested with Plasmodiophora brassicae, Woronin, were treated immediately after planting with a liquid or a granular surfactant. APSA 80™, applied in transplant water, significantly reduced percent clubbing and disease severity index (DSI) compared to control treatments. Miller Soil Surfactant Granular™ did not significantly reduce percent clubbing or DSI. There was a significant effect of cultivar on percent clubbing and DSI. There was no significant effect of transplant type on percent clubbing or DSI. This year's study culminates five years of investigation of surfactants for clubroot control. Specific surfactants have proven to be an effective control of clubroot in cabbage. Chemical names used: nonylphenoxypolyethoxyethanol (APSA 80™); alpha-alkanoic-hydro omega-hydroxy poly (oxyethylene) (Miller Soil Surfactant Granular™).

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Ginger Essential Oils-Loaded Nanoemulsions: Potential Strategy to Manage Bacterial Leaf Blight Disease and Enhanced Rice Yield

Molecules ◽

10.3390/molecules26133902 ◽

2021 ◽

Vol 26 (13) ◽

pp. 3902

Author(s):

Abdullahi Adamu ◽

Khairulmazmi Ahmad ◽

Yasmeen Siddiqui ◽

Intan Safinar Ismail ◽

Norhayu Asib ◽

...

Keyword(s):

Antibacterial Activity ◽

Electron Microscope ◽

Essential Oils ◽

Disease Severity ◽

Rice Yield ◽

Cell Structure ◽

Leaf Blight ◽

Bacterial Leaf Blight ◽

Control Treatment ◽

Promising Alternative

The bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most serious rice diseases, causing huge yield losses worldwide. Several technologies and approaches have been opted to reduce the damage; however, these have had limited success. Recently, scientists have been focusing their efforts on developing efficient and environmentally friendly nanobactericides for controlling bacterial diseases in rice fields. In the present study, a scanning electron microscope (SEM), transmission electron microscope (TEM), and a confocal laser scanning microscope (CLSM) were utilized to investigate the mode of actions of ginger EOs on the cell structure of Xoo. The ginger EOs caused the cells to grow abnormally, resulting in an irregular form with hollow layers, whereas the dimethylsulfoxide (DMSO) treatment showed a typical rod shape for the Xoo cell. Ginger EOs restricted the growth and production of biofilms by reducing the number of biofilms generated as indicated by CLSM. Due to the instability, poor solubility, and durability of ginger EOs, a nanoemulsions approach was used, and a glasshouse trial was performed to assess their efficacy on BLB disease control. The in vitro antibacterial activity of the developed nanobactericides was promising at different concentration (50–125 µL/mL) tested. The efficacy was concentration-dependent. There was significant antibacterial activity recorded at higher concentrations. A glasshouse trial revealed that developed nanobactericides managed to suppress BLB disease severity effectively. Treatment at a concentration of 125 μL/mL was the best based on the suppression of disease severity index, AUDPC value, disease reduction (DR), and protection index (PI). Furthermore, findings on plant growth, physiological features, and yield parameters were significantly enhanced compared to the positive control treatment. In conclusion, the results indicated that ginger essential oils loaded-nanoemulsions are a promising alternative to synthetic antibiotics in suppressing Xoo growth, regulating the BLB disease, and enhancing rice yield under a glasshouse trial.

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Association of Pathogenic Th17 Cells with the Disease Severity and Its Potential Implication for Biological Treatment Selection in Psoriasis Patients

Mediators of Inflammation ◽

10.1155/2020/8065147 ◽

2020 ◽

Vol 2020 ◽

pp. 1-16

Author(s):

Cristina Aguilar-Flores ◽

Octavio Castro-Escamilla ◽

Elizabeth M. Ortega-Rocha ◽

César Maldonado-García ◽

Fermín Jurado-Santa Cruz ◽

...

Keyword(s):

Disease Severity ◽

Peripheral Blood ◽

Th17 Cells ◽

Life Quality ◽

Severity Index ◽

Experimental Models ◽

Cutaneous Lesions ◽

Potential Implication ◽

Th17 Lymphocytes ◽

Pasi Score

Psoriasis is an inflammatory autoimmune disease characterized by cutaneous lesions in plaques. It has been proposed that the immune response has a key role in the disease progression. Particularly, the Th17 cells through IL-17 can contribute to maintain the inflammatory process. The pathogenic Th17 phenotype has been described in human diseases and associated with high severity in inflammatory experimental models. However, it is not clear if the pathogenic phenotype could be present in the skin and peripheral blood as well as its possible association to severity in psoriasis. In the lesional skin, we found high infiltration of Th17 cells and the pathogenic phenotype, finding a correlation between the frequency of Th17 cells and the Psoriasis Area and Severity Index (PASI) score. In peripheral blood, we observed a pool of Th17 lymphocytes with potential to acquire pathogenic features. Interestingly, the percentage of pathogenic Th17 cells (CD4+ RORγt+ IFN-γ+) correlates with disease severity. Moreover, we distinguished three groups of patients based on their IL-17/IFN-γ production by Th17 lymphocytes, which seems to be related with a dynamic or stable potential to express these cytokines. Remarkably, we evaluated the cytokine production by Th17 cells as an immunological marker for the adequate selection of biologic therapy. We found that patients analyzed by this immunological approach and treated with antibodies against IL-17 and TNFα showed great improvement depicted by reduction in PASI and Dermatology Life Quality Index (DLQI) score as well as the percentage of Body Surface Area (BSA). Altogether, our results highlight the importance of the assessment of the pathogenic phenotype in Th17 cells as an immune personalized analysis with the potential to support the therapy choice in the clinical practice.

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