Uso de extrato pirolenhoso no manejo em pós-emergência de plantas daninhas

Abstract

The resistance of weeds to herbicides, as well as the increasing demand from society for products increasingly free of pesticides, has created the need to discover biological products known as bioherbicides, which can act in the suppression of weeds. Among the bioinputs that have herbicidal potential, we can mention pyroligneous extract, a branched-chain carboxylic mixture derived from wood pyrolysis. Therefore, the aim of this study was to evaluate the herbicidal action of pyroligneous extract (PE) and its application in reducing doses of the herbicide 2,4-D. The experiments were conducted in a greenhouse at the Campus of Engineering and Agricultural Sciences. To evaluate the herbicidal action of PE, two types of extracts were used: the first produced in the laboratory from coconut and eucalyptus pyrolysis, and the second a commercial extract, associated with two adjuvants, mineral oil (0.5% v/v) and silicone oil (0.5% v/v). The design was completely randomized, with five concentrations of pyroligneous extract (0; 6.25%; 12.5%; 25% and 50%) and five receptor plant species (Crotalaria juncea, Megathyrsus maximus, Senna obtusifolia, Hyptis suaveolens, and Bidens spp.), with each combination of extract with adjuvant being an experiment. To evaluate the reduction of doses of 2,4-D with pyroligneous extract, a commercial pyroligneous extract was used, and the design was completely randomized in a 4x2 factorial scheme, with four mixtures of herbicide with PE (Distilled water; 0.5 L/ha of 2,4-D + 1 L/ha of PE; 1 L/ha of 2,4-D + 0.5 L/ha of PE; and 1.5 L/ha of 2,4-D - recommended commercial dose), and the solution with only water and with mineral oil (0.5% v/v), with each species of receptor plant being an experiment. In the evaluation of the herbicidal potential of PE, it was found that, regardless of the type of extract, there was effective control and reduction of dry mass in all tested weed species, with emphasis on Hyptis suaveolens and Bidens spp., and the combination of PE with mineral oil was more efficient than silicone oil. In the trials for the reduction of doses of 2,4-D using PE, the control of the species Crotalaria juncea was not satisfactory, even at the commercial dose of the herbicide, except for the treatment with mineral oil (0.5% v/v). The species Senna obtusifolia and Bidens spp. showed satisfactory control and reduction of dry mass in all tested mixtures. Pyroligneous extract has herbicidal action and was effective in reducing doses of the herbicide 2,4-D. The phytotoxic action of PE can be attributed to its vast chemical composition, which can contribute to both the suppression of weeds and the enhancement of synthetic herbicide action. Keywords: Wood vinegar; Weed; Bioinputs.