Abstract

The lack of a diagrammatic scale to evaluate the cucumber target spot, caused by Corynespora cassiicola, led to the development of an assessment system for a faster and more reliable way to quantify this disease. So, a diagrammatic scale was elaborated considering the maximum and minimum severity limits of the disease observed in the field. The intermediate values followed logarithmic increments for the target spot symptoms (0.3%, 0.8%, 2%, 5%, 11.5%, 25%, and 46%). For validating the scale, eight raters quantified the disease severity on fifty leaves infected with different levels of the disease. Initially, the severity estimation was carried out without the aid of the scale. Then, the same raters used it to estimate the severity on the same leaves previously assessed. Assessments with the aid of the diagrammatic scale were more precise and accurate, according to most of the raters. The proposed diagrammatic scale was considered adequate to estimate the target spot severity in cucumber leaves, and it can be used in epidemiologic studies and in evaluation strategies for controlling this disease.

Highlights

  • The lack of a diagrammatic scale to evaluate the cucumber target spot, caused by Corynespora cassiicola, led to the development of an assessment system for a faster and more reliable way to quantify this disease

  • minimum severity limits of the disease observed in the field

  • eight raters quantified the disease severity on fifty leaves infected with different levels of the disease

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Summary

DIAGRAMMATIC SCALE TO EVALUATE TARGET SPOT SEVERITY IN CUCUMBER PLANT LEAVES

The lack of a diagrammatic scale to evaluate the cucumber target spot, caused by Corynespora cassiicola, led to the development of an assessment system for a faster and more reliable way to quantify this disease. The proposed diagrammatic scale was considered adequate to estimate the target spot severity in cucumber leaves, and it can be used in epidemiologic studies and in evaluation strategies for controlling this disease. A escala diagramática proposta foi considerada adequada para estimar a severidade da mancha alvo, em folhas de pepineiro, e poderá ser utilizada em estudos epidemiológicos e de avaliação de estratégias de controle desta doença. O uso de escala diagramática, principal ferramenta na avaliação da severidade de manchas foliares, é muito importante para quantificação de doenças e necessário tanto para o estudo de medidas de controle, na determinação da eficiência de um fungicida ou na caracterização da resistência varietal, quanto para a epidemiologia, na construção de curvas de progresso da doença e estimativa dos danos provocados por ela (Amorim 1995). O objetivo deste trabalho foi elaborar uma escala diagramática de fácil utilização e que reproduza resultados precisos e acurados, visando a auxiliar estudos epidemiológicos e de controle de Corynespora cassiicola em pepineiro, em virtude do aumento da importância desta doença e da falta de informações sobre a interação pepineiro-Corynespora-ambiente

Elaboração da escala diagramática
Validação da escala diagramática
RESULTADOS E DISCUSSÃO
Com escala a
Avaliador BCDEFGH

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