Characterization, epidemiology and control strategies for the anthracnose pathogen (Colletotrichum spp.) on cashew (Anarcardium occidentale L.) in Mozambique

Abstract

The first confirmation of the presence of Colletotrichum gloeosporioides Penz. on cashew in Mozambique was based on a combination of observed symptoms, isolation and identification using basic morphological and molecular techniques. Anthracnose is now the second most important in the country, after powdery mildew caused by Oidium anacardii Noack. The present thesis represents a broad overview of the disease in Mozambique. The main focus of this study was thus to gather scientific information on the relevance of this disease in the country and through experimentation, generate recommendations that help farmers and decision makers to mitigate the disease pressure. The specific objectives of this study were as follows: - Provide a distinctive description of anthracnose symptoms on leaves through hostpathogen interaction studies in the laboratory. - Enhance current knowledge on the identity of Mozambican pathogen isolates, using DNA tools. - Assess the current anthracnose management practices, both at nursery and field level with a view to formulate timely, local and adequate management strategies. - Conduct experimental trials to select economically effective fungicides spraying programs for anthracnose disease management. ii - Search for variability and germplasm tolerance among dwarf and common cashew plant populations in Mozambique. By analyzing and integrating existing published literature on the subject, we successfully separated issues that concerned previously inaccessible information from those that reflect insufficient scientific knowledge. A survey was initiated to determine, the status of cashew anthracnose disease management practices in Mozambique. Subsequently, the information obtained was used to develop a national strategic framework for research and extension in the country. Areas identified as gaps were aligned with the main goals of this thesis and include: - Areas where scientific information lacked were identified. - The symptoms of the disease on leaves were successfully and distinctively distinguished from other common leaf diseases that simultaneously occur in orchards. - The pathogen isolates were identified using PCR techniques. The presence of Colletotrichum acutatum Simmonds was not confirmed at least not among the suspected and tested isolates. - Knowledge on the epidemiology of the disease was generated and its application for more effective disease management was successfully applied. - Effective fungicide applications and disease control programmes were developed for Colletotrichum gloeosporioides Penz.. - Appropriate nursery management strategies that reduce anthracnose disease development were developed. - Variability in germplasm reaction to the disease was demonstrated and therefore tolerant and susceptible genotypes were identified. - A technique for rapid and accurate evaluation of leaf anthracnose symptom grades was developed.