Uso de extratos vegetais no controle de Macrophomina phaseolina em sementes de feijão comum (Phaseolus vulgaris)

Abstract

Beans are an important agricultural crop for family farmers and, like other crops, production can be affected by various diseases. Grey stem rot, caused by the fungus Macrophomina phaseolina, is a soil-borne disease that affects this crop and can cause total crop loss. As an alternative to the use of synthetic fungicides in agriculture, the aim of this study was to evaluate the use of plant extracts of tobacco, castor bean and onion with garlic in the treatment of common bean seeds naturally infected with Macrophomina phaseolina. The extracts were obtained through maceration, resulting in an aqueous solution with a concentration of 2%. The experiment was set up in a completely randomized design with 4 treatments (3 treatments with plant extracts + 1 control). In order to assess the physiological potential of the seeds, germination, seedling emergence and seedling length tests were carried out. There were no differences between the treatments for the germination test, Emergence Speed Index (ESI), dry matter mass of the aerial part of the seedlings and root length. Only the treatments with castor bean extract and garlic extract with onion differed from the other treatments in the average length of the aerial part of the seedlings (8.852cm; 8.096cm) and the mass of root dry matter (0.0135 g; 0.0142 g). However, the treatment with garlic and onion extract was inferior to the other treatments in the 54% emergence test. In order to assess the fungal inhibition effectiveness of the extracts, plant health and establishment tests were carried out with and without water deficit, where the extract treatments showed no fungal action on the seeds. However, in the plant establishment experiment, insecticidal effects were observed in all the extract treatments, with the highest percentage (38.33%) of attacked plants in the control treatment and the lowest percentage (0%) of attacked plants in the tobacco extract treatment. The 2% concentration of plant extracts used in the experiment was not effective in controlling the fungus Macrophomina phaseolina, but it also had no harmful effects on the seeds.