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Diagrammatic scale for assessment of torch ginger anthracnose severity

Anthracnose caused by the fungus Colletotrichum gloeosporioides (Penz.) Sacc. is an important disease of torch ginger [Etlingera elatior (Jack) Smith] in the Brazilian Northeast. Considering the inexistence of standard methods for assessment of this disease, a diagrammatic scale was developed with 1, 2, 4, 8, 16, 32, 64, 82 and 92% of diseased bracts area and tested for accuracy, precision and reproducibility of the estimative of anthracnose severity with and without using the scale. The diagrammatic key was validated by 10 raters, using 45 bracts with different levels of severity. Without the diagrammatic scale most of raters overestimated disease severity. With the scale raters obtained better levels of accuracy and precision, with absolute errors concentrated around 10%. Raters showed great repeatability (95%) and reproducibility (<FONT FACE=Symbol>³</FONT>90% in 75.6% of cases) of estimative by using the scale. The proposed diagrammatic scale was suitable for the evaluation of torch ginger anthracnose severity.

Etlingera elatior; Colletotrichum gloeosporioides; phytopatometry


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