Uso de extrato pirolenhoso no controle de capim-sempre-verde em diferentes estágios fenológicos

Abstract

The use of pesticides in food, associated with the increase in herbicide-resistant biotypes in crops, and the need for systems with greater environmental sustainability, have driven the search for new alternatives to be used in weed management. Pyroligneous extract (PE) is a product originating from the condensation of smoke resulting from the production of charcoal (slow pyrolysis) and can be used in various ways in agriculture, including as a herbicide. The objective of this study was to analyze the herbicidal effect caused by the pyroligneous extract applied via spraying in different phenological stages of Evergreen Grass. For this, 900 seeds were sown in pots, after germination for each period, 15, 30 and 45 days were counted, then the pyroligneous extract (EP) was applied at a concentration of 22% EP + 78% water to the seeds. three phenological stages without mineral oil and 22% EP + 77.5% water + 0.5% mineral oil for the three phenological stages with mineral oil, 15, 30 and 45 days after seed germination. For each phenological stage there were 5 repetitions, 4 evaluations were carried out 3, 7, 15 and 30 days after application (DAA) of the product. In the first evaluation carried out at 3 DAA, the 15 and 30 day stages obtained rates above 90% on the visual phytotoxicity scale. In this period for plants aged 45 days, the phytotoxic effect of EP had a lower impact on the scale, 40% and 60%, with and without mineral oil respectively. At 30 DAA, the 45-day stage obtained 70% and 80% damage on the visual scale of phytotoxicity, with and without mineral oil respectively. The 15-day stage with and without mineral oil and the 30-day stage without mineral oil did not show any regrowth, while for the 30-day stage with mineral oil and 45 days with and without mineral oil, the regrowth rates were 40%, 100% and 80%, respectively. Thus, we conclude that the pyroligneous extract studied can be used to control Evergreen Grass, demonstrating greater phytotoxicity and control efficiency in plants up to 30 days old. The efficiency is lower in more mature plants, such as those aged 45 days. The use of mineral oil did not favor the control of the species in this experiment.