Septoria vouacapoua n. sp. etiological agent of brown leaf spot of acapu, Vouacapoua americana

Abstract

This study was conducted at IPEAN (Institute of Research and Agricultural Experimentation of the North, Belém, Pará, Brazil) to determine the etiological agent of disease attacking the leaves of acapu, Vouacapoua americana Aubl. The disease was characterized by the presence of a large number of reddish brown spots distributed over the entire surface of the leaflet. Such spots were generally round, however sometimes they had an angular form when the nervures were also attacked. It was observed that the incidence of these lesions was more severe during the rainy season. The mean the temperature during the rainy season was 25 to 26°C and the relative humidity ranged between 80 and 90%. When leaf material exhibiting typical lesions was held in a moisture chamber spores emerged as cirri from the fructification bodies. When these spores were examined with the aid of a microscope they were identified as belonging to the genus Septoria. These spores were used to inoculate healthy seedlings of acapu. Pathogenicity of the microorganism was established only after these inoculations yielded a complete cycle of the disease. The authors propose the name of Septoria vouacapouae n. sp. for the etiological agent of this new species of imperfect fungus. Suggested control measures include research to find resistant verieties or on small area the use of chemicals such as maneb, mancozeb and copper fungicides gave satisfactory results. As far as the authors can determine this is the first time that this disease has been reported on.