INCIDÊNCIA NATURAL DE DOENÇAS FÚNGICAS EM VARIEDADES DE CANA-DE-AÇÚCAR EM RESPOSTA A APLICAÇÃO DE CALCÁRIO

Abstract

Brazil is the world's largest producer of sugarcane, however, several factors affect the productivity of this crop, among them are the inadequate use of field technologies, the permanent cultivation of few genotypes and phytosanitary problems. With regard to phytosanitary problems, the application of limestone to raise soil pH generally shows good results in reducing the incidence of fungal diseases. Therefore, the objective of this work was to evaluate the incidence of fungal diseases in sugarcane plantations in the presence and absence of limestone. The experimental design was a randomized block design, in a 2 x 10 factorial scheme, in which 10 cultivars (Genotype 01, Genotype 02, RB 93509, RB 00 2754, VAT 90 212, RB 96 2962, RB 86 3129, RB 99 2506, SP 79 1011, RB 95 1541) were used. cultivated in soil in the presence and absence of correction with limestone. The application of limestone was based on soil analysis. In each part of the experiment, leaves were collected that showed symptoms of diseases. After the collection, the material was sent to the laboratory to carry out the identification. Identification was performed through preparation of slides and visualization of fungal structures under an optical microscope. In the field, the diseases were quantified according to the visual observations of the symptoms, by examining diseased plants in each plot. The presence of charcoal, red streak and rust was observed. In the studied varieties, only SP 791011 showed symptoms of charcoal, both in the presence and absence of limestone. All varieties showed the incidence of red rot. Only the variety RB 00 2754 was affected by rust in the presence of limestone, demonstrating the positive influence of this input on the occurrence of this disease. The varieties RB 96 2962, RB 99 2506 and VAT 90 212 showed no symptoms of rust, both in presence and absence of limestone. All varieties are susceptible to red rot and the application of limestone has positively influenced the reduction of the incidence of rust on sugarcane.