ABSTRACT
Control of botrytis leaf blight caused by Botrytis squamosa in onions has been achieved with weekly spraying of fungicides. With the aim of rationalizing the excessive number of sprayings, the present study technically and economically evaluated a disease forecasting system in comparison with the conventional control system. An experiment of randomized block design with four replicates and four treatments was installed in 2020 in Rio do Sul City (Santa Catarina State, Brazil) using the onion cultivar ‘Empasc 352 - Bola Precoce’. For the conventional system, sprayings started 15 days after sowing and were performed weekly during the crop cycle with a treatment using protective fungicide and another treatment using systemic fungicide. For the forecasting system, using the same types of fungicides for each treatment, the system validated for three years by Marcuzzo & Haveroth when the estimated severity value (SE) reached 0.30 was adopted. The forecasting system had the protective fungicide reapplied if accumulated rainfall was 25mm. Area under the disease progress curve, final severity, disease progression rate and yield did not differ between treatments, but the number of sprayings was 62.5% smaller in the forecasting system with the protective and systemic fungicides than in the weekly application system. The forecasting system allowed a cost reduction of R$ 306.00 (Brazilian real) using the systemic fungicide, in comparison with the conventional system, and of R$ 160.00/hectare using the protective fungicide. Adopting the forecasting system has proved to be a useful tool for the management of botrytis leaf blight of onions in Santa Catarina State, Brazil, and is available for the production chain at http://www.ciram.sc.gov.br/agroconnect/.
Keywords
Allium cepa
;
Botrytis squamosa
; integrated disease management; warning system
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