A global review of 25 countries indicated around three times as many indigenous forest pests (a total of 344 insect, pathogen and other species reported) as introduced click here ones (101 species), and that most of the introduced pests (72 species) occurred only in planted forests (FAO, 2009). Many recently-emerged infectious diseases are caused by fungal and fungal-like pathogens such as Fusarium circinatum. This serious disease has caused widespread

mortality of P. radiata in its natural range, is a serious problem in nurseries ( Steenkamp et al., 2014), and hampers planting in South Africa ( Mitchell et al., 2013). The transfer of conifer germplasm from affected regions to countries that are thus far free of this disease (e.g., Australia and New Zealand) is strictly controlled, meaning that further genetic infusions from natural stands into Australasian breeding populations cannot in practice occur. Despite phytosanitary

measures, a number of significant pest and disease outbreaks have occurred in Asia and Australasia during the last decade. In Australia, Selleck Romidepsin a recent (identified in 2010) introduction of Puccinia psidii, an exotic rust that threatens a broad range of native Myrtaceous genera (e.g., Corymbia, Eucalyptus and Melaleuca; Pegg et al., 2012), has spread rapidly in wild coastal forests and plantings. Some tree species have Org 27569 been found to have little resistance to the

disease and work is being undertaken to determine which are most at risk; containing the disease is now thought to be impossible. In the humid tropics, Ceratocystis spp. diseases of acacias ( Tarigana et al., 2011) have become widespread, particularly in Indonesia and Malaysia. Acacia mangium, the most important plantation species in many tropical lowland locations, appears to have very little resistance to Ceratocystis, and where disease occurs growers are often forced to plant other, less-productive tree species. In India and parts of Southeast Asia (notably Thailand), the Middle East and Africa, extensive damage to eucalypt plantations (particularly E. tereticornis, E. camaldulensis and hybrids involving these species) has been caused by a gall wasp, Leptocybe invasa ( Kim et al., 2008). Again, this has forced growers to deploy alternative species and hybrids. Restricting the spread of these diseases is a major challenge. In many parts of the world, this and invasiveness features (see Section 4.2) have led policymakers to focus their attention on the potential negative consequences of transferring tree germplasm. These risks partly explain why germplasm transfer is being increasingly controlled, in some cases even beyond the agreed phytosanitary regulations. Climate change is posing another challenge for containing the spread of pests and diseases.