1 Sirex noctilio has resulted in one of the most damaging biological invasions of pine forestry in the southern hemisphere. 2 An intensive, integrated control programme has been developed for this pest and is generally considered very successful. However, a critical comparison of S. noctilio infestations and control efforts throughout the southern hemisphere reveals that control has not been uniformly effective. Of particular concern is the apparently unexplained variability in establishment and success of biological control agents, including various parasitic wasps and the parasitic nematode Deladenus siricidicola . 3 An overlooked aspect in the establishment of the biological control interventions for S. noctilio is the potential influence of genetic bottlenecks on the ability of the agents to adapt to different environments and different populations of S. noctilio . 4 Despite established biological control agents, stress in forests caused by silvicultural practices or the environment will predispose trees to heavy infestation. Unfortunately, improved silvicultural practices are not always economically feasible and environmental changes are often unavoidable. 5 Sirex noctilio continues to pose a serious threat to pine forestry in many areas.Despite extensive earlier research into a single integrated control for S. noctilio , it is important to recognize that such a strategy will probably require significant local adaptation in new areas of infestation and over time.

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International trade and movement of people are largely responsible for increasing numbers of non-native insect introductions to new environments. For forest insects, trade in live plants and transport of wood packaging material (WPM) are considered the most important pathways facilitating long-distance invasions. These two pathways as well as trade in firewood, logs, and processed wood are commonly associated with insect infestations, while "hitchhiking" insects can be moved on cargo, in the conveyances used for transport (e.g., containers, ships), or associated with international movement of passengers and mail. Once established in a new country, insects can spread domestically through all of the above pathways. Considerable national and international efforts have been made in recent years to reduce the risk of international movement of plant pests. International Standards for Phytosanitary Measures (ISPMs) No. 15 (WPM), 36 (plants for planting),

Biological control is a valuable and effective strategy for controlling arthropod pests and has been used extensively against invasive arthropods. As one approach for control of invasives, exotic natural enemies from the native range of the pest are introduced to areas where control is needed. Classical biological control began to be used in the late 1800s and its use increased until, beginning in 1983, scientists began raising significant concerns and questions about nontarget and indirect effects that can be caused by these introductions. In recent years, similar issues have been raised about augmentative use of exotic natural enemies. Subsequently, international guidelines, national regulations and scientific methods being used for exotic natural enemies in biological control have changed to require appropriate specificity testing, risk assessment and regulatory oversight before exotic natural enemies can be released. National and international standards aimed at minimizing risk have increased awareness and promoted more careful consideration of the costs and benefits associated with biological control. The barriers to the implementation of classical and augmentative biological control with exotic natural enemies now are sometimes difficult and, as a consequence, the numbers of classical biological control programs and releases have decreased significantly. Based in part on this new, more careful approach, classical biological control programs more recently undertaken are increasingly aimed at controlling especially damaging invasive arthropod pests that otherwise cannot be controlled.We examine evidence for these revised procedures and regulations aimed at increasing success and minimizing risk. We also discuss limitations linked to the apparent paucity of postintroduction monitoring and inherent unpredictability of indirect effects.

Understanding the evolutionary histories of invasive species is critical to adopt appropriate management strategies, but this process can be exceedingly complex to unravel. As illustrated in this study of the worldwide invasion of the woodwasp Sirex noctilio, population genetic analyses using coalescent-based scenario testing together with Bayesian clustering and historical records provide opportunities to address this problem. The pest spread from its native Eurasian range to the Southern Hemisphere in the 1900s and recently to Northern America, where it poses economic and potentially ecological threats to planted and native Pinus spp. To investigate the origins and pathways of invasion, samples from five continents were analysed using microsatellite and sequence data. The results of clustering analysis and scenario testing suggest that the invasion history is much more complex than previously believed, with most of the populations being admixtures resulting from independent introductions from Europe and subsequent spread among the invaded areas. Clustering analyses revealed two major source gene pools, one of which the scenario testing suggests is an as yet unsampled source. Results also shed light on the microevolutionary processes occurring during introductions, and showed that only few specimens gave rise to some of the populations. Analyses of microsatellites using clustering and scenario testing considered against historical data drastically altered our understanding of the invasion history of S. noctilio and will have important implications for the strategies employed to fight its spread. This study illustrates the value of combining clustering and ABC methods in a comprehensive framework to dissect the complex patterns of spread of global invaders.

-The potential distribution of sirex wood wasp (Sirex noctilio) in Australia, South America and Africa (where the insect is known to occur and is spreading) and North America and China (where sirex has not established) was assessed from a study of the insect's current distribution and host range. Sirex noctilio has a wide host range, mainly in Pinus, including many important commercial species planted as exotics in the Southern Hemisphere as well as native stands in North America. Using the climate-matching program CLIMEX the potential distribution range of S. noctilio was predicted across the globe based on climatic conditions in Eurasia and northern Africa, where the insect is endemic. Sirex noctilio is predicted to establish in the majority of commercial Pinus plantations in Australia. Many countries with commercial Pinus plantations in South America (Uruguay, Brazil, Argentina, Chile and Paraguay) as well as South Africa are predicted to be colonised by S. noctilio by natural migration. Countries that are a long distance from S. noctilio-infested areas, such as Ecuador, Colombia, Venezuela, Zimbabwe, Tanzania, Uganda, Ethiopia and plantations in southern Chile, western Australia and north-western Brazil, are only likely to be colonised by S. noctilio via human-assisted transport of infested wood. Sirex noctilio was predicted to be able to persist in many areas in North America. In China, S. noctilio is predicted to be able to persist in many areas where large-scale afforestation of susceptible hosts has occurred and is planned. However, S. noctilio is endemic in neighbouring countries of China, indicating that something other than climate and host is restricting S. noctilio establishing in China, or that it has not been detected yet. The Sirex Management Strategy will help reduce the spread and impact of S. noctilio.

Native to Australasia, Eucalyptus (sensu lato) is one of the most planted genera of trees in the world. However, the sustainability of Eucalyptus species as plantation trees in non-native areas is increasingly threatened by the introduction and spread of Eucalyptus-feeding insects fromAustralia. We examine patterns and potential trends with respect to the global spread of Eucalyptusfeeding insects. Likely pathways of introduction and drivers of the rapid distribution of these insects, as well as management options are considered. The rate of introductions is shown to have increased nearly fivefold since the 1980s. As a result, the number of non-native pests of eucalypts outside of Australia has doubled in less than three decades. Furthermore, the rate of secondary spread among continents has also increased. Surprisingly, we found no association between area planted and the number of pests or new introductions. Only a small number of countries have been the points of first detection outside the native range; these countries have acted as bridgeheads to other regions.Quarantine regulations aimed at reducing the spread of invasive organisms appear to be ineffective at a global scale, and pathways allowing these invasions to occur are poorly understood or unknown. An expanded suite of management options are needed to provide resilience against the rapid accrual and homogenization of eucalypt pests, thereby ensuring the sustainability of eucalypt forestry worldwide.

Classical biological control (CBC) is the introduction of a natural enemy of exotic origin to control a pest, usually also exotic, aiming at permanent control of the pest. CBC has been carried out widely over a variety of target organisms, but most commonly against insects, using parasitoids and predators and, occasionally, pathogens. Until 2010, 6158 introductions of parasitoids and predators were made against 588 insect pests, leading to the control of 172 pests. About 55% of these introductions were made against pests of woody plants. Establishment rates of natural enemies and success rates were higher in CBC projects targeting pests of woody plants than other pests. This review aims to answer the questions most commonly asked regarding CBC against insect pests, with particular emphasis on tree pests. The topics covered include, among others: variations in rates of successes among different systems, different target insect groups and different agents; temporal trends in CBC practices and successes; economic and environmental benefits; risks and ways to mitigate the risks; CBC against native pests; accidental successes through the adoption of the invasive pests by native natural enemies or accidentally introduced agents; and prospects and constraints for the practice of CBC in the future. Questions are answered based on the analysis of two databases, the BIOCAT2010 database of introductions of insect biological control agents for the CBC of insect pests, and a database of introductions of entomopathogens against insect pests.