Diseases of eucalypt plantations in China: challenges and opportunities

In order to meet the needs of a rapidly growing local economy, plantations of Eucalyptus spp. have been extensively developed in China during the course of the past 20 years. Despite the fact that they threaten long term sustainability, very little work has been conducted on diseases and insect pests of Eucalyptus species in the Country. In an effort to expand the base of knowledge regarding eucalypt diseases in China, surveys have been undertaken in major plantation areas, including those in Guangdong, Guangxi, and Hainan. In this review, the most important diseases of Eucalyptus in China, as they have emerged from surveys and other recent Studies are considered. Identification of pathogens has been achieved based on morphology of the apparent causal agents and in some cases DNA sequence comparisons have been employed. The most obvious stem diseases encountered in China are bacterial wilt caused by Ralstonia solanacearum, stem cankers caused by Chrysoporthe cubensis, Kirramyces zuluensis, as well as species of Botryosphaeria and a Ceratocystis sp. Leaf and shoot diseases are also important and the more important pathogens include Kirramyces destructans, Kirramyces epicoccoides, Quambalaria pitereka as well as species of Cylindrocladium, Mycosphaerella and Pilidiella. This Study represents the first extensive survey Of eucalypt diseases in mainland China and it clearly shows that there are a great number of pathogens affecting plantations of these trees in the region. Studies have thus been initiated to further characterise the pathogens as well as to assess their relative importance. This will be followed by the development of strategies to reduce the impact of the most important diseases.