Ação da chuva sobre a eficiência de Glyphosate no controle de Eichhornia crassipes e Pistia stratiotes

Abstract

RESUMO -Com o objetivo de avaliar o efeito da chuva ocorrida em diferentes períodos de tempo após a aplicação do herbicida glyphosate, foram conduzidos dois estudos, sendo um com Eichhornia crassipes e outro com Pistia stratiotes. Ambos os experimentos foram instalados no delineamento inteiramente casualizado, com quatro repetições. Foi simulada uma chuva de 12 mm durante cinco minutos em diferentes períodos de tempo (0h, 2h, 4h, 6h, 12h, 24h e não simulação de chuva) após a aplicação de glyphosate, na dose de 2.160 g e.a. ha -1 (4,5 L p.c. ha -1 da formulação Rodeo) + 0,5% v/v de Aterbane. Foram realizadas avaliações visuais de controle das plantas daninhas aos 7, 14, 21 e 28 dias após a aplicação (DAA). O aumento do tempo sem a ocorrência de precipitações após a aplicação de glyphosate proporcionou maior eficiência no controle das duas espécies; o tratamento sem ocorrência de chuva e os com ocorrência a partir de duas horas da aplicação de glyphosate controlaram de forma visual as plantas de E. crassipes após 14 DAA e de P. stratiotes somente a partir de 21 DAA. O tratamento com ocorrência de chuva imediatamente após a aplicação do herbicida mostrou controle satisfatório das duas espécies de plantas daninhas aquáticas somente aos 28 DAA.Palavras-chave: aguapé, alface-d'água, herbicida, planta aquática, planta daninha.ABSTRACT -Two experiments were carried out to evaluate the effect of rain at different periods of time after glyphosate application, one with Eichhornia crassipes and the other with Pistia stratiotes, both arranged in a randomized design with four replications. The treatments consisted of simulating a 12 mm rainfall for five minutes, at different periods of time (0h, 2h, 4h, 6h, 12h, 24h, and no rain simulation) after glyphosate application at a dose of 2,160 g a.e. ha -1 (4.5 L c.p. ha -1 -Rodeo formulation) + 0.5% v/v aterbane. Visual evaluations of weed control at 7, 14, 21, and 28 days after application (DAA) were conducted. The increase in time without rainfall after glyphosate application provided an excellent control for the two species studied and the treatment without rainfall. The occurrence of rainfall after two hours of glyphosate application effectively controlled E. crassipes plants after 14 DAA and P. stratiotes after only 21 DAA. Treatments with rainfall immediately after herbicide application showed a good control for the two species of aquatic weeds only at 28 DAA.Keywords: hyacinth plant, water lettuce, herbicide, aquatic plant, weed. INTRODUÇÃONos sistemas aquáticos, em razão da poluição, das alterações dos níveis dos lagos e represas, ou por outras atividades promovidas pelo homem, pode ser observado o efeito do desequilíbrio, externado pela presença de plantas daninhas aquáticas que até então passavam despercebidas ou não se mostravam problemáticas (Foloni & Pitelli, 2005).

Período de chuva após a aplicação de saflufenacil no controle de macrófitas aquáticas flutuantes

“…This is different from treatments with rain simulation immediately (zero minutes) after saflufenacil application, which presented a negative impact on its control effectiveness up to 41.25% for the occurrence of rain 30 minutes after application, compared to the treatment without rain. Souza et al (2011b) studies the occurrence of rain after the pulverization of glyphosate (Roundup Rodeo formula) in controlling water hyacinth plants, even if this an herbicide with a different mode of action; it was observed that the occurrence of rain immediately (0 hours) after the application of the herbicide negatively influenced its phytotoxic effect on water hyacinth plants. Researchers highlighted the need for a minimum interval of two hours between the application of the herbicide and the occurrence of rain in order to have an effective control over water hyacinth plants.…”

“…Chemical control through the use of herbicides is the most used method to control these species, and it presents an elevated usage potential (Souza et al, 2011a;Campos et al, 2012;Kelly et al, 2012). However, the environment where these species occur may interfere in the absorption and translocation of herbicides, as well as the species foliar morphology, the herbicide characteristics and by the climate conditions during pulverization (Feng et al, 2000;Souza et al, 2011b;Campos et al, 2012;.…”

“…As for climate conditions, studies conducted to demonstrate the action of rain over the effectiveness of herbicides after their application during water plants post-emergence highlighted that they may cause a reduction in control effectiveness when they occur right after application, as well as climate conditions before application interfere in the effectiveness of herbicides (Anderson and Arnold, 1984;Souza et al, 2011b;Campos et al, 2012;Campos et al, 2013).…”

Distribution pattern, surface tension and contact angle of herbicides associated to adjuvants on spraying and control of Ipomoea hederifolia under rainfall incidence

“…Glyphosate has the best control when the interval between application and rainfall occurrence is higher , SOUZA et al 2011. Therefore, the time interval between application and the occurrence of rain and the amount and intensity of the rain, dosage and concentration of herbicides used influenced the effectiveness of the weed control (BRYSON 1988 The dry matter after 20 mm of rainfall was higher for all treatments, thus reducing the power of weed control, except for the only paraquat treatment, which demonstrated no difference in dry matter with or without simulated rain (Table 5).…”

Action of rain on the efficiency of herbicides applied post-emergence in the control of Senna obtusifolia

“…Deuber (1982), cites studies showing that the absorption of herbicides is limited by the amount that passes through the leaf cuticle, and that this is influenced by environmental conditions, by the species of weed and by the characteristics of the herbicides. The immediate consequence of this is less absorption and the consequently lower efficiency of the herbicide (SOUZA et al, 2011).…”