Comparison of the efficacy of QoI fungicides, alone or in mixture with triazoles, in Asian soybean rust control, 2016/17 growing season
AUTOR(ES)
Reis, Erlei Melo
FONTE
Summa phytopathol.
DATA DE PUBLICAÇÃO
2019-03
RESUMO
RESUMO Tem sido relatada a evolução da redução da sensibilidade de Phakopsora pachyrhizi às misturas dos três mecanismos de ação sítio-específicos (IDMs, IQes e ISDHs) usadas no seu controle. O objetivo desse trabalho foi quantificar a contribuição atual dos IQes, isolados ou em mistura com triazpois, no controle da ferrugem asiática da soja. Em experimento conduzido no campo comparou-se a eficácia dos inibidores da quinona externa (IQes), ou estrobilurinas, no controle da ferrugem da soja. Foram avaliados os efeitos isolados de quatro doses da azoxistrobina, picoxistrobina, piraclostrobina e trifloxistrobina e de quatro aplicações durante o ciclo da cultura. Comparou-se também o controle das misturas comerciais desses IQes com triazóis. Avaliou-se a severidade em quatro estádios fenológicos, calculou-se o controle com dados da severidade final, com dados da área abaixo da curva de progresso da ferrugem, a desfolha, a massa de mil grãos, o rendimento de grãos e o dano causado pela doença. A menor eficácia média no controle da ferrugem resultou das aplicações da azoxistrobina (15,8 e 11,19%) e da piraclostrobina (15,4 e 16,76%) e a maior para a picoxistrobina (54,1 e 54,35%) e trifloxistrobina (69,7 e 64,46%) calculada respectivamente com dados da severidade final e da AACPD. Essa eficácia não é suficiente para cobrir o custo da aplicação dos fungicidas, embora tenha sido observado reflexo positivo dos tratamentos no controle e no rendimento de grãos.ABSTRACT Evolution has been reported for the reduction in Phakopsora pachyrhizi sensitivity to the mixtures of the three site-specific mechanisms of action (DMIs, QoIs and SDHIs) used in its control. The aim of this study was to quantify the current contribution of QoIs, alone or in mixture with triazoles, in the control of Asian soybean rust. In an experiment carried out in the field, the efficacy of quinone outside inhibitors (QoIs), or strobilurins, was compared for Asian soybean rust control. The isolated effects of four doses of azoxystrobin, picoxystrobin, pyraclostrobin and trifloxystrobin were evaluated, as well as of four applications during the crop cycle. Control by commercial mixtures of these QoIs with triazoles was also compared. Severity was evaluated in four phenological stages, and control was calculated based on final severity data, area under rust progress curve, defoliation, one-thousand-grain mass, grain yield and damage caused by the disease. The lowest mean of rust control efficacy resulted from applications of azoxystrobin (15.8 and 11.19%) and pyraclostrobin (15.4 and 16.76%) and the highest mean was found for picoxystrobin (54.1 and 54.35 %) and trifloxystrobin (69.7 and 64.46%), calculated based on final severity and AUDPC, respectively. Such efficacy is not enough to cover the fungicide application cost, although there was a positive effect of treatments on disease control and grain yield.
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