Infection Rates in Three Pathosystem Epidemics Initiated With Reduced Disease Severities

Plaut, J. L.

doi:10.1094/phyto-71-917

Cited by 21 publications

(14 citation statements)

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“…However, a 60-80% reduction of ascospore formation as reached with applications of the antagonist Limonomyces roseipellis was not sufficient to control tan spot because of secondary conidiation [Pfender et al, 1993]. For three other polycyclic pathosystems including B. cinerea on Begonia semperflorens, Plaut and Berger [1981] found that initially low inoculum densities were compensated for by higher rates of disease increase compared to initially high inoculum densities. Thus, reduction of initial inoculum alone by biological control or other means may not always result in efficient disease control.…”

Section: Discussionmentioning

confidence: 94%

Suppression of sporulation ofBotrytis spp. as a valid biocontrol strategy

Köhl¹,

Molhoek²,

Plas³

et al. 1995

Eur J Plant Pathol

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In this study, the hypothesis was tested that removal of substrate for sporulation of Botrytis spp. may lead to a retardation of an epidemic if the majority of the inoculum is produced inside the treated crop.Suppression of sporulation of Botrytis spp. could be an attractive option for biological control of Botrytis leaf spot in onions. In a field experiment, necrotic leaf tissue was removed to simulate the effect of a biocontrol agent. By this means, the amount of substrate on which Botrytis spp. sporulates was reduced.In the experiment, the spore load above the onion plots was significantly reduced and the epidemic of onion leaf spot was retarded. At the end of the growing season, the number of leaf lesions in the green leaf area was lower in plots with substrate removal than in control plots (0.6 and 1.1 cm -2, respectively). The results demonstrated that an epidemic of onion leaf spot largely depends on the rate of inoculum production inside a crop. Thus, suppression of sporulation on necrotic leaf tissue is a valid control strategy that could be applied by using sporulation suppressing antagonists.

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Section: Discussionmentioning

confidence: 94%

Suppression of sporulation ofBotrytis spp. as a valid biocontrol strategy

Köhl¹,

Molhoek²,

Plas³

et al. 1995

Eur J Plant Pathol

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“…Rates and upper asymptotes varied between leaf layers and years, but were constant across contrasting inoculum treatments. The finding that r did not vary significantly with initial inoculum conflicts with other reports, from a range of pathosytems, that lower levels of initial inoculum were associated with higher disease progress rates (MacKenzie, 1976; Lim, 1978; Gregory et al ., 1981; Plaut & Berger, 1981; Rouse et al ., 1981; Berger & Jones, 1985). Hence, independence of r and initial inoculum should be tested for each experimental system, rather than assumed.…”

Section: Discussionmentioning

confidence: 99%

“…However, the high disease severities recorded here required the use of a logistic function to represent disease progress, in order to estimate Δ t . Plaut & Berger (1981) proposed a function to relate Δ t , the sanitation ratio (analogous to the inoculum ratios in this study), and r for logistic disease progress curves with upper asymptotes fixed at 100%. When converted to the notation used here, Δ t = (logit x 0 – logit x 0v )/ r .…”

Section: Methodsmentioning

confidence: 99%

Predicting epidemics of yellow rust (Puccinia striiformis) on the upper canopy of wheat from disease observations on lower leaves

Young

Paveley

Vaughan³

et al. 2003

Plant Pathology

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Data from field experiments were used to test whether disease observations on lower leaves of wheat were good predictors of future epidemic development in the upper canopy. Fungicide treatments to replicated plots in 1994 and 1995 caused variation in levels of initial inoculum of urediniospores of yellow rust ( Puccinia striiformis ). Observations of symptom severity were made on individual leaf layers throughout the season. Sporulating lesions on lower leaves were considered to be a measure of inoculum source strength for transfer to upper culm leaves. Low source strengths were associated with delays in epidemic development on the upper leaves, as quantified by a location parameter, t m , the time at which severity reached half of the asymptote value in logistic fits to disease progress data on the upper leaves. However, there was much unexplained variation, probably due to extraneous variation in upward transfer efficiency of inoculum and rates of epidemic development. Vanderplank's sanitation ratio theory was used to account for variation in inoculum transfer and epidemic rate. The analysis revealed that if the aim is to predict disease on a newly emerged culm leaf, during the period when it can be treated effectively with fungicide, then observations of disease two leaves further down the culm were of the greatest predictive value ( R 2 = 86%). These observations, however, need to be integrated with information about factors affecting upward inoculum transfer and rates of epidemic development if acceptable predictive precision is to be achieved.

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“…A interpretação do modelo Logístico para o oídio do cajueiro segue o proposto por Madden et al (13), onde no início a doença é ausente ou baixa devido à proteção com enxofre; se expande quando finaliza o período protetor (taxa crescente) e diminui a partir do aumento da quantidade de tecido doente (panícula). Neste caso, depois do período de proteção, o aumento da taxa de progresso compensa o baixo nível de inóculo potencial (infectivo) no início da epidemia, como sugerido por Plaut & Berger (16).…”

Section: Discussionunclassified

Progresso do oídio em função da fenologia do cajueiro

et al. 2018

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RESUMOO oídio (Pseudoidium anacardii) reduz quantitativa e qualitativamente a produção do cajueiro em diferentes regiões do Brasil. Severas epidemias ocorrem com frequência, iniciando-se durante a floração e se estendendo até o final do ciclo de produção da planta. O progresso da doença está relacionado à densidade de inóculo na área com cajueiros, aos fatores ambientais e à suscetibilidade dos órgãos para a infecção. Face a inexistência de informações sobre a epidemiologia dessa doença, objetivou-se caracterizar o progresso do oídio do cajueiro-anão em função da fenologia da planta. Foram aplicados seis tratamentos correspondentes aos períodos de proteção fenológica, com a aplicação de fungicida à base de enxofre, para quantificar a severidade do oídio nas panículas em duas floradas sucessivas. A partir Martins, M.V.V.; Lima, J.S.; Cardoso, J.E.; Viana, F.M.P.; Ootani, M.A. Progresso do oídio em função da fenologia do cajueiro. Summa Phytopathologica, v.44, n.2, p.178-184, 2018. dos dados coletados, foram geradas curvas de progresso da doença ajustadas a modelos lineares. O modelo Monomolecular foi o que melhor se ajustou às curvas de progresso do oídio nas panículas nas épocas I e II na ausência de proteção com enxofre. No modelo Monomolecular as taxas de progresso do oídio foram maiores na época I em relação à época II. Por outro lado, o modelo Logístico apresentou o melhor ajuste quando se introduziu o enxofre para proteger as panículas e reduzir a epidemia. Para maiores períodos de proteção, não foi possível ajustes de modelos em função da baixa severidade do oídio. É possível utilizar o modelo Monomolecular para estimar a taxa de doença e, o atraso do início da epidemia está diretamente relacionado ao aumento da proteção das panículas. Palavras-chave: Anacardium occidentale; Pseudoidium anacardii; modelos epidemiológicosO cajueiro (Anacardium occidentale L) é afetado por diferentes problemas fitossanitários que interferem na sua produção (7). Os danos são em termos quantitativos pela diminuição da produção de castanhas e pedúnculos e qualitativos quando interferem diretamente no desenvolvimento e no aspecto comerciável desses órgãos, principalmente quanto se trata do consumo do pedúnculo in natura. Devidos aos danos causados, o controle da doença deve ser adotado precocemente antes do início da epidemia. A epidemia inicia quando o hospedeiro emite as floradas e se estende durante todo o ciclo de produção da planta com menores taxas observadas nas floradas seguintes. O pico de doença, nas condições do semiárido nordestino, ocorre principalmente no primeiro fluxo de floração, influenciado pelo ambiente, pela agressividade do patógeno e pela suscetibilidade do cajueiro. Os botões e as flores das panículas são os órgãos mais suscetíveis à infecção (11, 19), mas constatam-se infecções após essa fase, tanto no pedúnculo quanto na castanha na fase de maturi (fruto jovem do cajueiro). Apesar de registrada em várias regiões do Brasil, a doença é mais frequente na região Nordeste, ocorrendo durante toda floração ...

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Infection Rates in Three Pathosystem Epidemics Initiated With Reduced Disease Severities

Cited by 21 publications

References 0 publications

Suppression of sporulation ofBotrytis spp. as a valid biocontrol strategy

Suppression of sporulation ofBotrytis spp. as a valid biocontrol strategy

Predicting epidemics of yellow rust (Puccinia striiformis) on the upper canopy of wheat from disease observations on lower leaves

Progresso do oídio em função da fenologia do cajueiro

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