Tropical Plant Pathology (2010) 35, 258-262

Mercia I.B. Celoto and Marli F.S. Papa (2010)
Elaboração e validação de escala diagramática para quantificação da mancha alvo em folhas de acerola
[Design and validation of diagrammatic scale for assessment of target spot in Barbados cherry leaf]
Tropical Plant Pathology 35 (4), 258-262
Abstract: The objective of this work was to design and validate a diagrammatic scale to assess target spot severity, caused by Corynespora cassiicola, in leaves of Barbados cherry. Leaves with different levels of severity were collected in the field. Following the Weber-Fechner visual stimulus Law, a scale was designed with 2, 4, 8, 16, 32 and 48% of diseased leaf areas. Validation was carried out by 10 evaluators, without previous practice in assessing diseases, who estimated the severity on 50 leaves with different levels of symptoms measured by the software Image Tool. The accuracy and precision of each rater was determined by simple linear regression between actual and estimated severity. The scale provided good levels of accuracy and precision and the absolute errors were around 10%. In addition, the coefficient of determination (precision of estimates) presented an average of 90% with the aid of the scale, and 78% without the aid of scale. The proposed scale proved to be adequate for severity assessments of target spot of Barbados cherry.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
(original language: Portuguese)
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Research topic(s) for pests/diseases/weeds:
surveys/sampling/distribution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Corynespora cassiicola	Malpighia (genus)	Brazil (south)