Management with Chemicals

Fry, William E.

doi:10.1016/b978-0-12-356401-6.50019-x

Cited by 3 publications

(1 citation statement)

References 90 publications

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“…The application of pesticides only during the first observation of the pest may lead to ineffective control and can result in buildup of the inoculum over time and eventually disease outbreak in an area (Fry, 1977). It is required to investigate into alternative natural plant products (Tripathi and Dubey, 2004), microbial antagonists (Droby et al, 1991) and the application of improved sanitary practices (Sierra et al, 1993;Wilson et al, 1995) in order to reduce the risks associated with ineffective application of chemicals and its environmental and health considerations.…”

Section: Management Of Preharvest Diseases and Insect Pests Of Citrusmentioning

confidence: 99%

Citrus Production, Constraints and Management Practices in Ethiopia: The Case of <i>Pseudocercospora<i> Leaf and Fruit Spot Disease

Dagnew¹,

Belew²,

Admassu³

et al. 2014

Sci. Technol. Arts Res. J.

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Article Information Citrus is economically important fruit crop in Ethiopia. However, its production is seriously constrained by various diseases including Pseudocercospora leaf and fruit spot. Surveys were conducted between June 2012 and May 2013 in the main citrus production areas of the country to assess the spread of the disease, and to determine its incidence and severity. A total of forty-nine citrus orchards in twenty-eight districts were surveyed. Random sampling techniques were used for data collection. The results showed that the disease had prevailed and widely spread in the districts assessed in the wet humid areas of the south, southwest, northwest, and north central parts, but not in the low altitude drier areas of the central rift valley and the eastern region of the country. Accordingly, 63.3% of the orchards surveyed were infected with the disease. The overall mean incidences of the disease on leaves of sweet orange, mandarin, lemon and lime were 36.2, 21.5, 17.1 and 16.3% while disease severity ratings were 2.6, 2.3, 2.0 and 1.7, respectively. Similarly, the average incidences and severities on fruits were 63.8, 29.4, 18.0 and 16.7%, and 4.0, 3.0, 2.0 and 2.0, in the same order. However, disease incidences in the different orchards ranged from zero to 76.7% on leaves and from zero to 100% on fruits. Disease severity ratings also varied from one to five on both leaves and fruits. In general, citrus orchards in the south and southwest Ethiopia that are known to have high rainfall and humidity conditions were more severely affected by the disease than those in the northwest and north central parts of the country. In these areas, respondents indicated that many farmers completely abandoned their citrus trees due to this disease. The causative agent was also identified to be the fungus Pseudocercospora angolensis based on cultural and morphological characteristics, and pathogenicity tests of representative isolates obtained from infected leaf and fruit samples.

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Section: Management Of Preharvest Diseases and Insect Pests Of Citrusmentioning

confidence: 99%

Citrus Production, Constraints and Management Practices in Ethiopia: The Case of <i>Pseudocercospora<i> Leaf and Fruit Spot Disease

Dagnew¹,

Belew²,

Admassu³

et al. 2014

Sci. Technol. Arts Res. J.

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Postinfection Activity of Selected Late Blight Fungicides

2000

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Two sets of experiments were done in the greenhouse with ‘Russet Burbank’ potatoes infected with Phytophthora infestans. The first determined the effectiveness of selected late blight fungicides in restricting lesion length and spore production when applied after stem lesions had occurred on potted plants. The second quantified the curative activity of selected fungicides applied 12 to 48 h after inoculation of excised leaves with P. infestans. Such information may be beneficial in selecting an effective fungicide for late blight management when symptoms of the disease are present in a field. Expansion of established stem lesions was consistently restricted by one application of either dimethomorph plus mancozeb or metiram plus triphenyltin hydroxide. Sporulation on established stem lesions was consistently inhibited by either one application of dimethomorph plus mancozeb or cymoxanil plus mancozeb. Two applications of propamocarb hydrochloride plus chlorothalonil were required to restrict lesion expansion and inhibit sporulation. Size and number of lesions and sporulation on leaflets were reduced when propamocarb hydrochloride plus chlorothalonil was applied up to 48 h after inoculation.

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Peach Rusty Spot Epidemics: Management with Fungicide, Effect on Fruit Growth, and the Incidence-Lesion Density Relationship

2003

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Different numbers of consecutive fungicide applications, beginning at petal fall and continuing into the summer, were examined for their effect on rusty spot epidemics. Disease progressions for each fungicide level were quantified by fitting either the logistic or monomolecular model. When the weighted absolute infection rate (ρ) and maximum disease level (Kmax) parameters were expressed as functions of the number of applications, the logistic decline model provided the best fit for five of six data sets. This model described a gradual decrease in ρ and Kmax in response to the initial fungicide application, a rapid decline in parameter values with the addition of one or two applications, and a diminished parameter response as fungicide applications continued toward the end of the epidemic. Based on examination of model behavior across all 3 years of the study, adequate management was achieved with a total of three to five fungicide applications. Additional analyses of area under the disease progress curve and final disease intensity at harvest supported these results and indicated that further reduction in fungicide usage may be possible. Unlike earlier findings, rusty spot did not significantly decrease fruit volume or weight at midseason or at harvest; as lesion density increased, fruit volume remained constant. The relationship between disease incidence and lesion density within any given year was best explained by the zero-intercept version of the exponential model. However, comparison of model parameters across years revealed significant seasonal variation. Nevertheless, the incidence-lesion density relationships were fairly uniform across years at incidence values below 0.5, where lesion density increased gradually and in a near-linear fashion.

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Management with Chemicals

Cited by 3 publications

References 90 publications

Citrus Production, Constraints and Management Practices in Ethiopia: The Case of <i>Pseudocercospora<i> Leaf and Fruit Spot Disease

Citrus Production, Constraints and Management Practices in Ethiopia: The Case of <i>Pseudocercospora<i> Leaf and Fruit Spot Disease

Postinfection Activity of Selected Late Blight Fungicides

Peach Rusty Spot Epidemics: Management with Fungicide, Effect on Fruit Growth, and the Incidence-Lesion Density Relationship

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