ABSTRACT
Occurrence of Botrytis leaf blight can reduce the productivity and compromise the quality of the bulb. The aim of this study was to evaluate the relationship between incidence and severity on the intensity of Botrytis leaf blight. The experiment was conducted with the cultivar “EMPASC 352 – Bola precoce” at Catarinense Federal Institute/Rio do Sul Campus. Design was in randomized blocks with four replicates and six treatments consisting of fungicide application according to the forecasting system proposed by Marcuzzo & Haveroth (2016) with estimates of accumulated severity (ES) of 0.20, 0.25, 0.30, compared to application at every 5 and 7 days and control, without spraying, in order to promote a disease intensity gradient for the years 2017 and 2018. The disease intensity was weekly evaluated based on the severity and incidence. Data were subjected to linear regression analysis. The equation of best fit was adopted for the two seasons and the severity value of 1% was replaced, yielding an incidence of 11.93%. Estimating severity based on the incidence and the opposite allows technical assistance team to use it in the monitoring of Botrytis leaf blight. As the evaluation of incidence is more rapid, accurate and reproducible, according to the obtained data, severity can be estimated based on the incidence, facilitating the disease quantification by the technical assistance team.
Keywords
Allium cepa; Botrytis squamosa; disease intensity
