Teratosphaeria stem canker of Eucalyptus: two pathogens, one devastating disease

BACKGROUND: Teratosphaeria gauchensis and T. zuluensis are closely related fungi that cause Teratosphaeria (previously Coniothyrium) stem canker disease on Eucalyptus species propagated in plantations for commercial purposes. This disease is present in many countries in which Eucalyptus trees are planted, and continues to spread with the international trade of infected plant germplasm. TAXONOMY: Fungi, Ascomycota, Pezizomycotina, Dothideomycetes, Dothideomycetidae, Capnodiales, Teratosphaeriaceae, Teratosphaeria. IDENTIFICATION: The causal agents form dark masses of pycnidia that are visible on the surface of distinct stem cankers that typically form on young green stem tissues. Accurate diagnosis of the causal agents requires DNA sequence data. HOST RANGE: Nine species of Eucalyptus are known to be affected. Of these, E. grandis and its hybrids, which include some of the most important planting stock globally, appear to be particularly vulnerable. DISEASE SYMPTOMS: Small necrotic lesions develop on young green stem tissue. These lesions coalesce to form large cankers that exude gum. Epicormic shoots develop below the girdling canker and, in severe cases, trees die. USEFUL WEBSITES: Mycobank, https://www.mycobank.org; Publications of the Forestry and Agricultural Biotechnology Institute (FABI), https://www.fabinet.up.ac.za/index.php/journals.