scholarly journals Optimization of Chemical Suppression of Alternaria dauci, the Causal Agent of Alternaria Leaf Blight in Carrots

Plant Disease ◽  
2001 ◽  
Vol 85 (11) ◽  
pp. 1149-1156 ◽  
Author(s):  
E. Ben-Noon ◽  
D. Shtienberg ◽  
E. Shlevin ◽  
H. Vintal ◽  
A. Dinoor
Keyword(s):  
Field Experiments ◽  
Threshold Model ◽  
Disease Onset ◽  
Leaf Blight ◽  
Copper Hydroxide ◽  
Control Efficacy ◽  
Alternaria Leaf Blight ◽  
Major Constraint ◽  
Action Threshold ◽  
Alternaria Dauci

Alternaria leaf blight, caused by Alternaria dauci, is a major constraint to carrot production in Israel. Israeli carrot growers apply prophylactic sprays at 3- to 10-day intervals throughout the season until harvest, up to 30 sprays in a growing season. In this study, we attempted to optimize the chemical suppression of the disease, in order to reduce fungicide use. The efficacy of nine fungicides was determined in two field experiments. All fungicides reduced disease severity, but there were significant differences in efficacy among them. The most effective were difenoconazole and chlorothalonil; less effective were copper hydroxide, tebuconazole, trifloxystrobin, and mancozeb; the least effective in our experiments were flutrifol, propineb, and iprodione. The effect of the time of spray initiation on fungicide efficacy was determined in three field experiments. Qualitative (analysis of variance) and quantitative (regression) analyses of the data revealed that initiating sprays after disease onset reduced control efficacy. Thus, an action threshold model could not be developed for A. dauci in carrots. The time before harvest at which sprays could be terminated was tested in two field experiments and it was found that terminating sprays 14 days before harvest did not significantly affect the overall control efficacy. The main conclusions derived from these experiments were tested and corroborated in two additional field experiments.

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

HortScience ◽  
2008 ◽  
Vol 43 (5) ◽  
pp. 1522-1527 ◽  
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.

Influence of rate of soil fertilization on alternaria leaf blight (Alternaria dauci) in carrots

1999 ◽  
Vol 27 (3) ◽  
pp. 193-200 ◽  
Author(s):  
H. Vintal ◽  
E. Ben-Noon ◽  
E. Shlevin ◽  
U. Yermiyahu ◽  
D. Shtienberg ◽  
...  
Keyword(s):  
Leaf Blight ◽  
Soil Fertilization ◽  
Alternaria Leaf Blight ◽  
Alternaria Dauci

scholarly journals First report of alternaria leaf blight caused by Alternaria dauci on carrot in Turkey

2005 ◽  
Vol 54 (2) ◽  
pp. 252-252 ◽  
Author(s):  
S. Soylu ◽  
S. Kurt ◽  
E. M. Soylu ◽  
F. M. Tok
Keyword(s):  
Leaf Blight ◽  
First Report ◽  
Alternaria Leaf Blight ◽  
Alternaria Dauci

scholarly journals Joint Action of Disease Control Measures: A Case Study of Alternaria Leaf Blight of Carrot

2003 ◽  
Vol 93 (10) ◽  
pp. 1320-1328 ◽  
Author(s):  
E. Ben-Noon ◽  
D. Shtienberg ◽  
E. Shlevin ◽  
A. Dinoor
Keyword(s):  
Host Resistance ◽  
Drip Irrigation ◽  
Chemical Control ◽  
Control Measure ◽  
Leaf Blight ◽  
Control Measures ◽  
Disease Suppression ◽  
Control Efficacy ◽  
Alternaria Leaf Blight ◽  
Cultural Measures

The efficacy of chemical (i.e., foliar fungicide sprays), genetic (i.e., moderately resistant cultivars), and cultural (i.e., drip-irrigation system) control measures was quantified individually and in combination in the management of Alternaria dauci, the causal agent of Alternaria leaf blight of carrot. Whereas host resistance and drip irrigation affected both the time of disease onset and the rate of disease progression, chemical control affected only the latter. In all cases, a single control measure did not provide an acceptable level of disease suppression. Control efficacy values (based on the relative area under the disease progress curve) for chemical, genetic, and cultural control were 58 ± 11, 39 ± 20, and 60 ± 22%, respectively (values are means ± standard error). By contrast, implementing two control measures concurrently always improved disease suppression significantly compared with the individual measures. Control efficacy values were 91 ± 8% for the integration of chemical and genetic measures and 82 ± 23% for the integration of chemical and cultural measures. Moreover, yields in plots protected by two control measures simultaneously were higher by 10.1 to 28.6 t/ha than those in the respective plots protected by single measures. The joint effect of chemical control and host resistance was additive, whereas that of chemical control and drip irrigation was synergistic in most cases. A literature review was performed to determine if these findings represent a general relationship between chemical and genetic, and chemical and cultural measures. Based on 19 reviewed cases, it was concluded that additive effects are the rule and synergistic or antagonistic effects are the exception. Synergistic effects of two control measures were observed when one control measure improved the efficacy of the other directly or when one control measure induced host resistance or predisposed the pathogen to increased susceptibility. These results may enable a more effective selection of candidate control measures for integration in the future.

Impact of carrot resistance on development of the Alternaria leaf blight pathogen (Alternaria dauci)

2008 ◽  
Vol 121 (1) ◽  
pp. 55-66 ◽  
Author(s):  
Cora Boedo ◽  
Valérie Le Clerc ◽  
Mathilde Briard ◽  
Philippe Simoneau ◽  
Michel Chevalier ◽  
...  
Keyword(s):  
Leaf Blight ◽  
Alternaria Leaf Blight ◽  
Alternaria Dauci

scholarly journals Management of Xanthomonas Leaf Blight of Onion with a Plant Activator, Biological Control Agents, and Copper Bactericides

Plant Disease ◽  
2005 ◽  
Vol 89 (6) ◽  
pp. 631-639 ◽  
Author(s):  
David H. Gent ◽  
Howard F. Schwartz
Keyword(s):  
Biological Control ◽  
Field Experiments ◽  
Leaf Blight ◽  
Disease Suppression ◽  
Biological Control Agents ◽  
Copper Hydroxide ◽  
In Planta ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Bulb Yield

Xanthomonas leaf blight (Xanthomonas axonopodis pv. allii) is a yield-limiting disease of onion (Allium cepa) in the western United States. Frequent applications of copper-based bactericides amended with an ethylenebisdithiocarbamate fungicide (e.g., maneb or mancozeb, class B2 carcinogens) provide some disease suppression, but strategies to reduce conventional bactericide use are needed to minimize grower costs, environmental impact, and public exposure to class B2 pesticides. Applications of acibenzolar-S-methyl reduced in planta and epiphytic populations of X. axonopodis pv. allii as effectively as applications of copper hydroxide-mancozeb in growth chamber studies. Under field conditions, four weekly applications of acibenzolar-S-methyl reduced severity of Xanthomonas leaf blight as or more effectively than 9 to 12 weekly applications of copper hydroxide or copper hydroxide-mancozeb. Acibenzolar-S-methyl applications did not increase bulb yield or grade compared with copper bactericide treatments. However, bulb yield was reduced 22 to 27% when 10 weekly applications of acibenzolar-S-methyl were made in the absence of disease. Application of a commercial formulation of both Pantoea agglomerans strain C9-1 and Pseudomonas fluorescens strain A506 reduced severity of Xanthomonas leaf blight in field experiments. Weekly copper hydroxide applications starting 1 to 2 weeks before bulb initiation were as effective as weekly applications started 3 to 4 weeks before bulb initiation, irrespective of the maneb rate used. Integration of acibenzolar-S-methyl and biological control agents with copper hydroxide in a carefully timed spray program may eliminate the use of the class B2 carcinogens maneb and mancozeb on onion without compromising efficacy for management of Xanthomonas leaf blight.

scholarly journals Influence of Gibberellic Acid on Carrot Growth and Severity of Alternaria Leaf Blight

Plant Disease ◽  
2000 ◽  
Vol 84 (5) ◽  
pp. 555-558 ◽  
Author(s):  
P. Santos ◽  
J. J. Nunez ◽  
R. M. Davis
Keyword(s):  
Gibberellic Acid ◽  
Growth Habit ◽  
Leaf Length ◽  
Leaf Blight ◽  
Root Weight ◽  
Root Cortex ◽  
Alternaria Leaf Blight ◽  
Alternaria Dauci ◽  
Plant Emergence ◽  
Root Quality

Applications of gibberellic acid (GA) to carrot foliage consistently reduced the percentage of leaf area affected by Alternaria dauci compared with nontreated plants. The degree of leaf blight reduction with two applications of GA was similar to that achieved with four applications of the fungicide iprodione. At the rates examined (GA at 2.5 to 250 mg/liter), foliage dry weights were generally increased by GA. Although root weight was significantly reduced by rates of 250 mg/liter, applications of lower rates (40 mg/liter or less) reduced leaf blight severity without affecting root quality. Applications of GA usually resulted in plants with longer leaves, wider petioles, and a more upright growth habit. In one trial, leaf length and petiole diameter increased linearly with increasing rates (20, 30, and 40 mg/liter). When applied twice at 30 mg/liter, GA did not affect cuticle, epidermal, or leaf thickness. In general, the initial timing of two applications of 20 to 40 mg/liter (4, 6, or 8 weeks after plant emergence) did not influence the effects of GA. However, in one trial, there was a greater incidence of core separation from the root cortex when 40 mg/liter was applied initially at 4 weeks. GA at 30 mg/liter slightly but significantly decreased inner root color in one of two trials.

scholarly journals Development of a weather-based forecasting model for Alternaria leaf blight of carrot

2019 ◽  
Vol 45 (4) ◽  
pp. 413-414
Author(s):  
Leandro Luiz Marcuzzo ◽  
Carolina Maria Tomasoni
Keyword(s):  
Linear Regression Analysis ◽  
Beta Function ◽  
Logistic Function ◽  
Leaf Blight ◽  
Forecasting Model ◽  
Leaf Wetness ◽  
Leaf Wetness Duration ◽  
Influence Of Temperature ◽  
Alternaria Leaf Blight ◽  
Alternaria Dauci

ABSTRACT In the present study, under controlled conditions, the influence of temperature (10, 15, 20, 25 and 30°C) and leaf wetness duration (6, 12, 24 and 48 hours) was studied on the severity of Alternaria leaf blight of carrot caused by Alternaria dauci. The relative density of lesions was influenced by temperature and leaf wetness duration (P<0.05). The disease was more severe at the temperature of 25°C. Data underwent non-linear regression analysis. The generalized beta function was used for fitting the data on disease severity and temperature, while a logistic function was chosen to represent the effect of leaf wetness duration on the severity of leaf blight. The response surface resulting of the product of the two functions was expressed as ES = 0.004993 * (((x-8)1.13125) * ((36-x)0.53212)) * (0.39219/(1+25.93072 * exp (-0.16704*y))), where: ES represents the estimated severity value (0.1); x, temperature (ºC) and y, leaf wetness duration (hours). This model must be validated under field conditions to be used as a forecasting model for Alternaria leaf blight of carrot.

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