Desenvolvimento e validação de escala diagramática para avaliação da Sigatoka amarela da bananeira

Abstract

Banana (Musa spp.) is cultivated in all Brazilian regions, being the banana one of the most consumed fruits and of significant socioeconomic importance for the country. In areas with low productivity, the main associated factors are the lack of technification and inadequate management of pests and diseases. Among the diseases, the Yellow sigatoka leaf spot (Mycosphaerella musicola) stands out, responsible for causing a reduction in production above 50%. The objective of this work was to develop and validate a diagrammatic scale to assess the severity of the Yellow sigatoka leaf spot. The diagrammatic scale was developed and validated with eight severity levels (0.44, 5.43, 12.80, 20.22, 40.26, 60.20, 72.83 and 91.28%). Scale validation involved the participation of 14 raters without experience with the pathosystem. Three assessments were carried out at weekly intervals. In the first evaluation, 50 images of symptomatic leaves were presented to the evaluators, and the severity values were estimated without the aid of the scale. In subsequent evaluations, the evaluators used the scale. Data were analyzed by two methods: simple linear regression and Lin's coefficient of agreement. By means of simple linear regression, without the scale, the intercept values of 92.86% of the evaluators differed significantly from zero. With the use of the scale, in the first and second evaluations, there was a reduction in the percentage of evaluators with significant intercept values, to 57.14% and 28.57%. Using Lin's coefficient of agreement, the deviation correction factor was 0.918 and 0.991, without and with the use of the scale, respectively. Lin's correlation coefficient of agreement was 0.857 and 0.946, without and with the use of the scale, respectively. Without the scale, most raters overestimated the severity of the disease. With the use of the scale, there was high accuracy, precision, repeatability and reproducibility of estimates. Therefore, the diagrammatic scale developed in this study is recommended to assess the banana yellow Sigatoka.