Damage to foliage and stems caused by fungal pathogens in young eucalypt plantations in Zambia

Abstract

Plantations consisting of non-native tree species were established on the Copperbelt of Zambia to supplement timber supply from natural forests and to meet the increasing demand of round wood and fuel wood for the copper mines. In early 2004, a disease characterised by severe leaf defoliation and death of juvenile trees suddenly occurred in plantations of the Copperbelt Forestry Company. This study was undertaken to determine the nature of the disease and extent of damage caused with a view of providing a framework for sustainable management of the plantations. Disease incidence, severity and impact on plantations using the crown damage index were assessed for three consecutive years. Eucalyptus grandis was more affected than E. cloeziana and leaf spot incidence and severity were higher in Kalibu, Kitwe District, than in Kafubu, Kalulushi District. The incidence in Kalibu was 90.4%, causing tree crown damage of 18.6% at the end of the assessment in 2006 compared to 17.5% incidence and 1.02% crown damage recorded in Kafubu. Fungi collected from leaf tissues included species of Aulographina, Cryptosporiopsis, Cylindrocladium and fungi in the Teratosphaeriaceae. Stem pathogens were identified as fungi in the Botryosphaeriaceae and Kirramyces sp. Diseases induced by these pathogens are increasingly becoming major threats to young eucalypts, resulting in poor stem form. Factors favouring disease development are described and these need to be properly managed to minimise the impact of diseases in addition to the need to establish selection and breeding programmes to develop tolerant genotypes to ensure a sustainable future for the forestry industry in Zambia.