Dinâmica da remoção pela chuva de fungicidas utilizados no controle de ferrugem asiática da soja
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Data
2020-02-19
Autores
Araújo, Vitor Carvalho Ribeiro
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Universidade Estadual Paulista (Unesp)
Resumo
A aplicação de fungicidas com ação sítio específico aliado aos multissítios ou protetores tem sido a principal estratégia para o controle químico da ferrugem asiática da soja. Apesar da alta eficiência dessas misturas, os fungicidas associados a ela podem estar susceptíveis a remoção pela água da chuva, uma vez que as aplicações para o controle da doença coincidem com período de maior precipitação nas lavouras brasileiras. O objetivo deste trabalho foi determinar a resistência à remoção pela chuva de trifloxistrobina associada a fungicidas protetores em plantas de soja expostas à chuva simulada em intervalos de tempo sucessivos após a aplicação. O trabalho foi realizado em condição de casa de vegetação na estação experimental da Fundação Mato Grosso em Campo Verde, Mato Grosso, Brasil. Foi utilizado o esquema fatorial 4x4 (caldas fungicidas x intervalo de tempo entre a aplicação e a chuva simulada) e o delineamento experimental foi inteiramente casualizado com quatro repetições. Foi avaliado o fungicida trifloxistrobina aplicado isoladamente e em mistura com um dos fungicidas protetores: mancozebe, oxicloreto de cobre e clorotalonil. Foi adicionado óleo metilado de soja (0,25%) às caldas. Cada planta tratada foi submetida à chuva, em exposição única, a um determinado intervalo de tempo: 0, 60, 180 e 360 minutos após a aplicação. O equipamento utilizado para aplicação dos tratamentos trata-se de um simulador de pulverização e chuva portátil sob trilhos desenvolvido pelo laboratório de máquinas para pulverização da FCA/UNESP. As soluções provenientes da lavagem da planta tratada foram submetidas a cromatografia líquida de alta eficiência associado a espectrometria de massas (LC-MSMS) para identificação de trifloxistrobina. Os dados foram submetidos à análise de variância (ANOVA) e foi realizada a análise de regressão para determinação do modelo apropriado para descrever a relação entre quantidade de ingrediente ativo lavado e intervalo de tempo decorrido entre a aplicação e a chuva. Foi realizado o teste Tukey para comparação das médias da quantidade de fungicida removido entre as misturas de fungicidas dentro de cada intervalo de tempo. Houve interação entre as caldas fungicidas e o intervalo de tempo entre a aplicação e a chuva simulada. Os dados provenientes da lavagem de trifloxistrobina pela chuva simulada foram ajustados ao modelo logarítmico na presença de óleo metilado de soja (R² = 0,9851), óleo metilado de soja + clorotalonil (R² = 0,942) e óleo metilado de soja + oxicloreto de cobre (R² = 0,9372). O modelo logístico foi ajustado para óleo metilado de soja + mancozebe (R² = 0,9999), A associação de trifloxistrobina com mancozebe, clorotalonil ou oxicloreto de cobre reduziu a quantidade da estrobilurina removida em função da chuva, quando esta ocorrru imediatamente após a aplicação. No entanto, não foi verificada diferença entre os tratamentos para os intervalos de tempo entre a aplicação e a chuva de 60, 180 e 360 minutos. Portanto, os fungicidas multissítios protetores mancozebe, oxicloreto de cobre e clorotalonil associados ao fungicida trifloxistrobina aumenta a sua resistência à lavagem pela chuva, quando esta ocorre imediatamente após a aplicação em plantas de soja. O modelo logarítmico é o que melhor explica a relação de decréscimo da quantidade de trifloxistrobina removida pela chuva em função do intervalo de tempo decorrido entre a aplicação do fungicida e a chuva simulada com exceção da calda contendo mancozebe, em que o modelo logístico possui melhor ajuste.
The application of fungicides with specific site action combined with multisite or protectors has been the main strategy for the chemical control of Asian soybean rust. Despite the high efficiency of these mixtures, the fungicides associated with it may be susceptible to removal by rainwater, since the applications for the control of the disease coincide with a period of greater precipitation in Brazilian crops. The objective of this work was to determine the resistance to rain removal of trifloxystrobin associated with protective fungicides in soybean plants exposed to simulated rain at successive time intervals after application. The work was carried out in a greenhouse condition at the Mato Grosso Foundation experimental station in Campo Verde, Mato Grosso, Brazil. The 4x4 factorial scheme (fungicide spray solutions x time interval between application and simulated rain) was used and the experimental design was completely randomized with four replications. The fungicide trifloxystrobin applied alone and mixed with one of the protective fungicides was evaluated: mancozebe, copper oxychloride and chlorothalonil. Methylated soybean oil (0.25%) was added to the spray solutions. Each treated plant was subjected to rain, in a single exposure, for a certain time interval: 0, 60, 180 and 360 minutes after application. The equipment used to apply the treatments is a spray simulator and portable rain under rails developed by the FCA / UNESP spray machines laboratory. The solutions from the washing of the treated plant were subjected to high performance liquid chromatography associated with mass spectrometry (LC-MSMS) to identify trifloxystrobin. The data were submitted to analysis of variance (ANOVA) and regression analysis was performed to determine the appropriate model to describe the relationship between the amount of active ingredient washed and the time elapsed between application and rain. The Tukey test was performed to compare the averages of the amount of fungicide removed between the fungicide mixtures within each time interval. There was an interaction between the fungicide mixtures and the time interval between application and simulated rain. The data from the trifloxystrobin washing by simulated rain were adjusted to the logarithmic model in the presence of methylated soybean oil (R² = 0.9851), methylated soybean oil + chlorothalonil (R² = 0.942) and methylated soybean oil + copper oxychloride (R² = 0.9372). The logistic model was adjusted for methylated soybean oil + mancozebe (R² = 0.9999). The association of trifloxystrobin with mancozebe, chlorothalonil or copper oxychloride reduced the amount of strobilurin removed due to rain, when it occurred immediately after application. However, there was no difference between treatments for the time intervals between application and rain of 60, 180 and 360 minutes. Therefore, the protective multisite fungicides mancozebe, copper oxychloride and chlorothalonil associated with the fungicide trifloxystrobin increases its resistance to washing by rain, when it occurs immediately after application in soybean plants. The logarithmic model is the one that best explains the ratio of decrease in the amount of trifloxystrobin removed by the rain as a function of the time interval between the application of the fungicide and the simulated rain except for the spray solution containing mancozebe, in which the logistic model has the best adjustment.
The application of fungicides with specific site action combined with multisite or protectors has been the main strategy for the chemical control of Asian soybean rust. Despite the high efficiency of these mixtures, the fungicides associated with it may be susceptible to removal by rainwater, since the applications for the control of the disease coincide with a period of greater precipitation in Brazilian crops. The objective of this work was to determine the resistance to rain removal of trifloxystrobin associated with protective fungicides in soybean plants exposed to simulated rain at successive time intervals after application. The work was carried out in a greenhouse condition at the Mato Grosso Foundation experimental station in Campo Verde, Mato Grosso, Brazil. The 4x4 factorial scheme (fungicide spray solutions x time interval between application and simulated rain) was used and the experimental design was completely randomized with four replications. The fungicide trifloxystrobin applied alone and mixed with one of the protective fungicides was evaluated: mancozebe, copper oxychloride and chlorothalonil. Methylated soybean oil (0.25%) was added to the spray solutions. Each treated plant was subjected to rain, in a single exposure, for a certain time interval: 0, 60, 180 and 360 minutes after application. The equipment used to apply the treatments is a spray simulator and portable rain under rails developed by the FCA / UNESP spray machines laboratory. The solutions from the washing of the treated plant were subjected to high performance liquid chromatography associated with mass spectrometry (LC-MSMS) to identify trifloxystrobin. The data were submitted to analysis of variance (ANOVA) and regression analysis was performed to determine the appropriate model to describe the relationship between the amount of active ingredient washed and the time elapsed between application and rain. The Tukey test was performed to compare the averages of the amount of fungicide removed between the fungicide mixtures within each time interval. There was an interaction between the fungicide mixtures and the time interval between application and simulated rain. The data from the trifloxystrobin washing by simulated rain were adjusted to the logarithmic model in the presence of methylated soybean oil (R² = 0.9851), methylated soybean oil + chlorothalonil (R² = 0.942) and methylated soybean oil + copper oxychloride (R² = 0.9372). The logistic model was adjusted for methylated soybean oil + mancozebe (R² = 0.9999). The association of trifloxystrobin with mancozebe, chlorothalonil or copper oxychloride reduced the amount of strobilurin removed due to rain, when it occurred immediately after application. However, there was no difference between treatments for the time intervals between application and rain of 60, 180 and 360 minutes. Therefore, the protective multisite fungicides mancozebe, copper oxychloride and chlorothalonil associated with the fungicide trifloxystrobin increases its resistance to washing by rain, when it occurs immediately after application in soybean plants. The logarithmic model is the one that best explains the ratio of decrease in the amount of trifloxystrobin removed by the rain as a function of the time interval between the application of the fungicide and the simulated rain except for the spray solution containing mancozebe, in which the logistic model has the best adjustment.
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Palavras-chave
Tecnologia de aplicação, Trifloxistrobina, Fungicidas protetores, Phakopsora pachyrhizi, LC-MSMS