Controle de brotações de eucalipto por glyphosate em regime de reforma

Abstract

The eucalyptus has a great ability to emit sprouts after cutting, which allows the adoption of coppice, a management that presents advantages such as the rapid development of the new settlement and less impact on the environment. However, some factors may prevent the adoption of the coppice, being necessary to reform the settlement. In order to reform a forest of eucalyptus, it is necessary to control the undesirable buds, favoring the development of the new planting and the chemical method is the most used. Due to its efficiency and systemic action, the herbicide glyphosate is the most adopted for this operation. However, the control efficiency of shoots is variable and can be attributed to the formulations used, the dose of product used and the application technology involved. Therefore, two experiments were carried out to evaluate the efficiency of different formulations of glyphosate and its doses and two forms of application in the control of undesirable shoots of eucalyptus in the reform area. The first experiment was carried out in a 3 x 5 factorial scheme containing three formulations of glyphosate (isopropyl amine salt, potassium salt and ammonium salt), by applying five doses 1080, 1440, 1800, 2160 and 2520 g ha-1 of glyphosate. The second test was carried out in a 2 x 5 factorial scheme, containing two forms of application (short bar equipped with two XT020 tips and long bar, containing 2 AI11003 tip pairs, angled at 45 ° and targeted to the shoots and 5 doses (1080, 1440, 1800, 2160 and 2520 g ha-1). Glyphosate formulations interfered with the control of eucalyptus shoots. Initially at 15 days after application (DAA), the potassium salt formulation stood out with superior control to the others, however, in the other tests, the plants treated with the other formulations presented similar control. The level of control increased proportionally to the dose of product applied during the whole period evaluated. Plants treated with smaller doses showed recovery with the emission of new branches. The height of the treated plants was also influenced by the dose of glyphosate. Lower heights were observed for the shoots submitted to the dose of 2520 g ha-1. For treatments with lower doses, the emission of new shoots was elevated, with rates close to 40%. The application with long bar provided better coverage of the target, resulting in superior control of shoots at the end of the evaluated period. The control of shoots increased, according to the dose of glyphosate applied, also interfering with the height of the surviving buds. Applications with smaller doses allowed the recovery of the plants with the emission of new branches from the stump without the presence of intoxication symptoms. Thus, the use of the long bar, associated with the use larger doses of glyphosate, is efficient to control eucalyptus shoots under reform regime.