DIEBACK OF CASHEW (ANACARDIUM OCCIDENTALE) IN CAMEROON

Abstract

Cashew nut (Anacardium occidentale) is one of the most important cash crops of Far north Cameroon. A disease, named dieback was observed causing serious damage on many trees in some orchards of two mains production sites Maroua and Yagoua. Leaves and stems with symptoms of each attacked tree varieties were randomly extracted for isolation and identification of pathogens. The pathogen structures were characterized under light microscope. Incidence, severity and prevalence of disease were evaluated during the dry and rainy seasons. Pathogenicity test were performed with C. gloeosporioides conidia inoculation of healthy plants. The disease symptoms were first observed in leaves and on bark of stems. Orange brown necrosis were observed in leaves and stem of bark were dark. Both two symptoms lead to death of plant. Different gum exudations were observed on bark of infected trees. Lasiodiplodia sp and Colletotrichum gloeosporioides were identified using identification keys. Young conidia of Lasiodiplodia were hyaline and non septate, whereas mature conidia were brown, one septate, and striate. Pure culture of C. gloeosporioides is whitish in PDA medium. The disease seems to occur throughout the year, but it spreads faster during the rainy season. Incidence was higher in Yagoua site, 73 and 90 % respectively in dry season and rainy season. Severity was low whatever the site. Artificially inoculated plants (with C. gloesporioides) showed symptoms similar to those that were naturally infected. Yellow variety was more susceptible than red variety. Cashew dieback is spreading to all production areas in the Far North of Cameroon and remains a threat to cashew nut production by reducing tree growth and eventually cause plant death.