Plantation forestry based on Eucalyptus spp. has grown dramatically during the past 100years, mainly in the tropics and southern hemisphere where these trees are non-native. Early plantations were affected by pests and pathogens, although damage was generally minimal. This is a situation that is changing dramatically with serious pest and pathogen problems now emerging regularly and often times causing very serious damage. Given the growing movement of people and products around the world, this is a trend that is certain to continue and the threat of diseases and insect damage is now seen as one of the most important constraints to the future sustainability of Eucalypt plantation forestry globally. While this is a very troubling situation, there are also reasons to be optimistic. Established technologies such as breeding and selection of disease and insect resistant species and hybrids; enhanced through vegetative propagation have already shown substantial promise to reduce damage. Likewise, biological control is being effectively used to reduce damage due to invasive alien insect pests. New technologies including DNA-based tools for identification, detection and monitoring of pest and pathogens are increasingly valuable. Similarly, the growing availability of genome sequences for Eucalypts and for their pests and pathogens will increasingly add to our capacity to reduce damage. While there are unknown dangers such as the impact of climate change on the damage caused by pests and pathogens, we believe that continual and realistic investment in technology will ensure long term sustainability of Eucalypt plantation forestry. Failure to invest wisely will result in the collapse of plantation enterprises and concomitant loss in investments.