Seleção do local de aplicação e do estádio fenológico do algodoeiro para inoculação do agente da ramulose

Abstract

Ramulosis, caused by Colletotrichum gossypii var. cephalosporioides, is one of the most devastating diseases for cotton crops causing severe losses in Brazil. In addition to damping off and necrotic leaf spots, the disease also causes dwarfism, internodes shortening, apical blight and multiple sprouting of branches. In this study, the objective was to compare several methods of inoculating C. gossypii var. cephalosporioides in cotton, considering different growth stages and locations of inoculum deposition, aiming to reproduce the typical symptoms of the disease under controlled conditions. Inoculation was performed by applying an inoculum suspension of 106 conidia mL-1 on plants at phenological growth stages of V0, V2, and B1, placing the inoculum to the whole plant, to apical shoot, and to the whole plant except for the apical shoot. We verified that the most appropriate method for inoculation was in plants at the V2 growth stage with the application of inoculum to the whole plant. Inoculation of only the apical shoot was insufficient to reproduce the symptoms of ramulosis.