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Validation of a forecast system for Botrytis leaf blight of onion

Leandro Luiz Marcuzzo About the author


Aiming to validate a forecast system with different severity levels, compared to conventional spraying to control Botrytis leaf blight of onion, experiments were conducted in Rio do Sul, Santa Catarina State (SC), Brazil, during the crop seasons in 2017, 2018 and 2019. The spraying programs were established according to the daily values of estimated severity (ES) obtained by the system of Marcuzzo & Haveroth, assigning accumulated values of 20, 25 and 30 ES, and the conventional system with spraying at every 5 and 7 days, compared to the control not treated with fungicides. Except for control, there was no significant difference among treatments for productivity in all cycles. The area under the disease progress curve (AUDPC), the final severity and the disease progress rate did not differ among treatments, but the forecast system with ES of 30 allowed a number of spraying 40, 33 and 25% lower than the weekly application system in the three years of evaluation.

Allium cepa; plant disease forecaster; epidemiology; Botrytis squamosa

Grupo Paulista de Fitopatologia FCA/UNESP - Depto. De Produção Vegetal, Caixa Postal 237, 18603-970 - Botucatu, SP Brasil, Tel.: (55 14) 3811 7262, Fax: (55 14) 3811 7206 - Botucatu - SP - Brazil