Eficácia de extratos pirolenhosos de cana-de-açúcar (Saccharum officinarum L.) e eucalipto (Eucalyptus spp.) no controle in vitro de patógenos da soja

Abstract

Brazil is the third largest soybean producer in the world [Glycine max (L.) Merr.], which has great importance in business because of its significant participation in the socioeconomic context of the country. Production losses occur due to the attack of pathogens from different kinds of etiologies, highlighting the white mold (Sclerotinia sclerotiorum), anthracnose (Colletotrichum truncatum), charcoal rot (Macrophomina phaseolina) and Sclerotium wilt (Sclerotium rolfsii). This study aimed to evaluate the efficacy of pyroligeneous extracts (PE) of sugarcane (Saccharum officinarum) and eucalyptus (Eucalyptus spp.) in different concentrations for the in vitro control of Sclerotinia sclerotiorum, Macrophomina phaseolina, Colletotrichum truncatum and Sclerotium rolfsii. The experiments were conducted in a completely randomized design with six treatments and six repetitions for each pathogen. The concentrations 0, 1000, 2000, 3000, 4000 and 5000 ppm were tested in order to evaluate mycelial growth in millimeters (mm), mycelial growth rate index (IVCM), growth inhibition (%) for the four species of Fungi and carpogenic germination for Sclerotinia sclerotiorum. The eucalyptus PE at concentrations of 1000, 2000 and 3000 ppm favored the mycelial development of the fungus Sclerotinia sclerotiorum. For both extracts, concentrations of 4000 and 5000 ppm showed antifungal activity. The extracts, in general, presented fungitoxicity at different concentrations and the effect was higher in the first hours of contact with the fungus. Growth and mycelial growth velocity decreased as the doses increased. In the carpogenic germination of Sclerotinia sclerotiorum, sugarcane PE at 5000 ppm promoted a reduction in the percentage of germinated sclerotia. The PE hindered and modified the development of stapes and consequently reduced the formation of apothecia. In vivo research should be performed in order to prove the efficacy of the PE, assessing the reponses when there is environmental interaction in the field.