Sulfentrazone efficiency on Ipomoea hederifolia and ... 165 SULFENTRAZONE EFFICIENCY ON Ipomoea hederifolia AND Ipomoea quamoclit AS INFLUENCED BY RAIN AND SUGARCANE STRAW1 Eficácia de Sulfentrazone em Ipomoea hederifolia e Ipomoea quamoclit Influenciada pela Ocorrência de Chuva e Palha de Cana CORREIA, N.M.2, CAMILO, E.H.3, and SANTOS, E.A.4 ABSTRACT - The aim of this study was to assess the capacity of sulfentrazone applied in pre- emergence in controlling Ipomoea hederifolia and Ipomoea quamoclit as a function of the time interval between herbicide application and the occurrence of rain, and the presence of sugarcane straw on the soil surface. Two greenhouse experiments and one field experiment were conducted. For the greenhouse experiments, the study included three doses of sulfentrazone applied by spraying 0, 0.6, and 0.9 kg ha-1, two amounts of straw on the soil (0 and 10 t ha-1), and five time intervals between the application of herbicide and rain simulation (0, 20, 40, 60, and 90 days). In the field experiment, five herbicide treatments (sulfentrazone at 0.6 and 0.9 kg ha-1, sulfentrazone + hexazinone at 0.6 + 0.25 kg ha-1, amicarbazone at 1.4 kg ha-1, and imazapic at 0.147 kg ha-1) and two controls with no herbicide were studied. Management conditions with or without sugarcane straw on the soil were also assessed. From the greenhouse experiments, sulfentrazone application at 0.6 kg ha-1 was found to provide for the efficient control of I. hederifolia and I. quamoclit in a dry environment, with up to 90 days between herbicide application and rain simulation. After herbicide application, 20 mm of simulated rain was enough to leach sulfentrazone from the straw to the soil, as the biological effects observed in I. hederifolia and I. quamoclit remained unaffected. Under field conditions, either with or without sugarcane straw left on the soil, sulfentrazone alone (0.6 or 0.9 kg ha-1) or sulfentrazone combined with hexazinone (0.6 + 0.25 kg ha-1) was effective in the control of I. hederifolia and I. quamoclit, exhibiting similar or better control than amicarbazone (1.4 kg ha-1) and imazapic (0.147 kg ha-1). Keywords: Boral®, raw sugarcane, morning glory, herbicide retention, Saccharum officinarum. RESUMO - Objetivou-se neste trabalho avaliar o controle em pré-emergência de Ipomoea hederifolia e Ipomoea quamoclit pelo herbicida sulfentrazone em função do intervalo de tempo entre a aplicação e a ocorrência de chuva e da manutenção ou não de palha de cana-de-açúcar na superfície do solo. Três experimentos foram desenvolvidos: dois em casa de vegetação e um em campo. Nos experimentos em casa de vegetação, foram estudadas três doses de sulfentrazone (0, 0,6 e 0,9 kg ha-1) pulverizado em duas quantidades de palha na superfície do solo (0 e 10 t ha-1) e cinco intervalos de tempo entre a sua aplicação e a simulação de chuva (0, 20, 40, 60 e 90 dias). No experimento em campo, foram avaliados cinco tratamentos de herbicida (sulfentrazone a 0,6 e 0,9 kg ha-1; sulfentrazone + hexazinone a 0,6 + 0,25 kg ha-1; amicarbazone a 1,4 kg ha-1; e imazapic a 0,147 kg ha-1) e duas testemunhas sem aplicação. A manutenção ou não da palha de cana sobre o solo também foi estudada. Em casa de vegetação, a aplicação de 0,6 kg ha-1 de sulfentrazone foi suficiente para o controle adequado de I. hederifolia e I. quamoclit num ambiente seco com até 90 dias sem chuva após a aplicação. Os 20 mm de chuva simulados após a aplicação do herbicida foram suficientes para remover o sulfentrazone da palha para o solo, pois o efeito biológico de controle de I. hederifolia e I. quamoclit não foi alterado. Em campo, sem ou com a permanência de palha de cana sobre o solo, o sulfentrazone 1 Recebido para publicação em 15.2.2012 e aprovado em 20.8.2012. 2 Professor, Dr., Dep. de Fitossanidade, Universidade Estadual Paulista – UNESP, Campus de Jaboticabal-SP, Via de Acesso Prof. Paulo Donato Castellane, s/n 14.884-900 Jaboticabal-SP, <[email protected]>; 3 Engo-Agro., formado pela UNESP, Campus de Jaboticabal-SP; 4 Doutorando do Programa de Pós-Graduação em Agronomia - Produção Vegetal, UNESP, Campus de Jaboticabal-SP. Planta Daninha, Viçosa-MG, v. 31, n. 1, p. 165-174, 2013 166 CORREIA, N.M., CAMILO, E.H., and SANTOS, E.A. isolado (0,6 e 0,9 kg ha-1) ou em mistura com hexazinone (0,6 + 0,25 kg ha-1) foi eficaz para I. hederifolia e I. quamoclit, com resposta similar ou melhor que a do amicarbazone (1,4 kg ha-1) e imazapic (0,147 kg ha-1). Palavras-chave: Boral®, cana crua, corda-de-viola, retenção de herbicidas, Saccharum officinarum. INTRODUCTION attributes of the herbicides, such as solubility, vapor pressure, and polarity (Rodrigues, In the southeast and midwest regions of 1993). Rain or irrigation, time following the Brazil, sugarcane harvest begins in April or application of herbicide, and changes in the May, extending to November or December of chemical constitution of the decomposing plant the same year. After cutting, crop treatments material may also strongly influence herbicide such as weed management are necessary retention by straw (Correia et al., 2007). to ensure new sprouting and plant growth. When straw remains on the soil, herbicides During the drier periods of the year (June, are potentially lost by photodegradation, July, and August), herbicide application can volatilization, and even adsorption to plant be conducted during the pre-emergence, residues. The degree of decomposition or plant post-harvest, or post-emergence stages of residue age may affect its ability to adsorb the the crop, when the soil moisture has been herbicide (Mersie, 2006). restored. However, herbicides used during the On the experimental site of the present dry season should be highly water-soluble and study, there was increased infestation by vine have low or moderate soil adsorption to ensure species, including Ipomoea and Merremia that, even under low moisture conditions, part species, later in the growing season. It is of the product is desorbed to the soil solution possible that sugarcane straw remaining and will be available for absorption by the on the soil surface may create a favorable seedling radicle and/or hypocotyl. environment for the seed germination and the Sulfentrazone is listed as an herbicide for development of these weeds due to a reduced use in sugarcane production during the dry daily temperature range, increased soil season and is specifically recommended for moisture retention, and improved physical and the pre-emergence control of dicotyledonous chemical soil attributes. Correia and Durigan and monocotyledonous species in agricultural (2004) reported that the emergence of Ipomoea areas used for sugarcane, coffee, citrus, grandifolia, I. hederifolia, and I. quamoclit was eucalyptus, and soy crops as well as non- not influenced by straw at the levels included agricultural areas in Brazil. Sulfentrazone is in their study (5, 10, and 15 t ha-1). Contrary highly water-soluble (solubility = 490 mg L-1), to this finding, however, an increased number nonvolatile (vapor pressure = 1.0 x 10-9 mmHg of I. quamoclit seedlings emerged, and a greater at 25 oC), anionic (pK = 6.56), and hydrophilic biomass accumulation was observed, in the (Kow = 1.48) (Senseman, 2007; Rodrigues and presence of mulch compared to treatment Almeida, 2011). These parameters convey the without straw. stability of the molecule and its affinity for Approximately 74% of the Ipomoea and water, which underlie the potential losses of Merremia species found in southeastern Brazil the herbicide to the environment. are vine plants with versatile stems and Sugarcane mill factories and their branches that intertwine with neighboring suppliers have adapted to the application of plants and grow over obstacles (Kissmann herbicides during the dry season, but both and Groth, 1999). In addition to the damage have experienced difficulty with weed control they cause by competing for water, light, in recent years. Leftover and unburned straw nutrients, and space, these species cause from sugarcane cutting may compromise serious damage to sugarcane at harvest time the ability of residual herbicide to reach the because they compromise the performance of soil. The effect of straw on herbicide efficacy machines used for harvesting along with the depends on the physical and chemical quality of the harvested product. Planta Daninha, Viçosa-MG, v. 31, n. 1, p. 165-174, 2013 Sulfentrazone efficiency on Ipomoea hederifolia and ... 167 The present study was conducted to test quantities corresponding to the two treatment the hypothesis that sugarcane straw on the levels. The straw was cut into small fragments soil surface does not affect the herbicidal less than or equal to the diameter of the pots. efficacy of sulfentrazone, whose weed control The bottoms of the pots were covered with potential remains uncompromised for an a sheet of newspaper to prevent soil loss. Each extended period between the application pot was placed on a plastic container with a and the first occurrence of rain. The aim diameter larger than that of the pot and of this study was to assess the efficacy of without holes to ensure a consistent watering sulfentrazone, applied during the pre- regime. The soil moisture was monitored on a emergence period, for the control of daily basis. Water was added to the containers I. hederifolia and I. quamoclit, with different as needed and was distributed through the soil time intervals between herbicide application by capillary action. and the occurrence of rain, with or without sugarcane straw on the soil surface.