First Report of Red Rust Disease caused by Cephaleuros virescens on Mango (Mangifera indica) Tree in Cameroon

Abstract

In August 2020, a disease with symptoms identical to red rust caused by Cephaleuros virescens was found in orchards of mangoes besides orchards of Anacardium surveyed in Maroua and Garoua (Cameroon). The objective of this research was to study this disease with characterizing its causal organism using morphological methods. Mango leaves exhibiting clear symptoms of red rust with pathogen somatic and reproductive structures were used for morphological characterization and identification of the causal pathogen. Leaves were collected based on the symptoms, size and number of lesions associated. The survey results indicate that orange coloured,  small circular lesions were found on the upper leaf surfaces and coalescing in midrib were observed. Circular lesions on the leaves were of varied diameter from 1 to 5 mm with an average of 1.6 (coefficient of variation 34%). Among symptomatic leaves showing lesions, 60% were exhibiting lesions smaller than 2 mm in diameter.  The length and width of sporangiophores and sporangia were 237.62 - 4645.85 × 15.5 μm and 20.6 - 41.32 × 20.6 μm, respectively. Based on the symptoms observed and microscopic morphological studies, the recovered pathogen was identified as Cephaleuros virescens. This is the first report of algal leaf disease on M. indica in Cameroon.