EXTRATOS DE JUREMA PRETA NO CONTROLE DE MANCHA-DEALTERNARIA EM MELANCIA

Abstract

This study had the objective to evaluate the action of aqueous (EAC), ethanolic (EEC) and decoction (EDC) extracts of juremapreta bark Mimosa tenuifloraand aqueousroot extract (EAR) on the control of alternaria black spot on watermelon, as well as evaluating the mode of action of these extracts, either by presenting toxicity to the pathogen and the ability to alter the metabolism of the host by activating protective enzymes. M.tenuiflora extracts were tested for inhibition of germination, mycelial growth and sporulation of A.cucumerina in vitro. Under controlled conditions (in vivo), the plants were sprayed with the four extracts in three concentrations (05, 4.0 and 10 mg.mL-1) 48 hours before inoculation. The evaluations were based on disease severity and determination of enzymatic activity. In the field the four extracts were sprayed at two concentrations (4.0 and 10 mg.mL-1), evaluating the severity of the disease with the help of descriptive scale. The EAC inhibited 100% germination, mycelial growth and sporulation of A.cucumerina in vitro. The EAC induced synthesis of β-1,3 glucanase and peroxidase, reducing 97% of the disease, in a controlled environment and 31% in the field, being superior to the other extracts and commercial fungicides: copper oxychloride which controlled 79% and 21% for environmental controlled and field respectively, and tebuconazole + trifloxystrobin which controlled 15% in the field. These extracts showed potential to control alternaria leaf spot is caused toxicity to the pathogen or by inducing resistance.