First report of pink disease on Eucalyptus camaldulensis in Ethiopia

Abstract

Eucalyptus camaldulensis was one of the first Eucalyptus species to be introduced into Ethiopia, and it has been widely planted at low altitude, where warm conditions prevail. Wood from Eucalyptus plantations provides fuel, construction material and other forest products to local communities. Recently, disease symptoms that resemble those of pink disease were observed on E. camaldulensis planted at Pawe, Benshangul Gumuz region, north-western Ethiopia. These symptoms are common on E. camaldulensis trees growing at this locality . The disease is characterized by branch dieback, stem canker, production of epicormic shoots, production of pink mycelial growth on the surface of infected tissue, and eventually death of trees. Based on external symptoms, the disease on E. camaldulensis in Ethiopia was identified as pink disease (Ciesla et al ., 1996). To confirm the identity of the causal agent, the large subunit RNA (28S) operon was sequenced and analysed using Phylogenetic Analysis Using Parsimony (PAUP 4·0). The Ethiopian isolates were compared with two reference isolates of Erythricium salmonicolor (CBS 810·85 and CBS 168·82). Based on sequences (AF 506709), the Ethiopian and reference E. salmonicolor isolates grouped together with 100% confidence level, separate from any of the other Corticiaceae (CI = 0·6243; RI = 0·6964). Results of the sequence data analysis thus supported our preliminary identification. Isolates of E. salmonicolor obtained from Ethiopia have been deposited in the culture collection of FABI, University of Pretoria. Erythricium salmonicolor (synonym, Corticium salmonicolor ) is a member of the Corticiaceae (Basidiomycotina, Aphyllophorales). It attacks a wide range of hosts in the tropics, including Eucalyptus spp., coffee, rubber, cacao, tea and Acacia spp. (Gibson, 1975; Sharma et al ., 1984; Old et al ., 2000). Pink disease is a serious problem of Eucalyptus in India and Brazil (Ciesla et al ., 1996). Hence, the prevalence of this disease on a widely planted Eucalyptus species in Ethiopia is of great concern, not only to large-scale plantation development in the country, but also to rural tree growers who plant the tree to generate income. The impact of this disease on other Eucalyptus spp., as well as on other exotic and indigenous tree species in Ethiopia, is not known and will receive attention in the future.