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Although native to Australia, Eucalyptus species are found throughout Europe. At present, they are located mainly in the Iberian Peninsula and Eucalyptus globulus is the most commonly planted species. Climate forecasts anticipate an expansion of Eucalyptus to other regions of Europe. The fast growth of E. globulus, together with its resprouting ability and wood properties, has promoted the use of this species in the Iberian Peninsula. The total volume of E. globulus harvested there was close to 14 million m3 in 2019. Eucalyptus species represent the main source of raw material for the pulp and paper industries and provide an important source of income to non-industrial owners. Being exotic fast-growing trees, their expansion has also been associated with negative environmental impacts. The species therefore poses a series of challenges, while also generating opportunities. The objectives of this review paper are: (1) to summarize the importance of Eucalyptus plantations in Europe; (2) to analyse the opportunities and challenges of this genus in present and future plantations in Europe; (3) to assess to what extent forest management, at both stand and landscape levels, can reduce negative impacts; (4) to make policy and management recommendations that may support the use of this genus in other European regions. These aims are accomplished based on a thorough literature review, particularly focused on research developed in the Iberian Peninsula. [ABSTRACT FROM AUTHOR]

• A 3-PG.d simulator was used to compare management strategies against G. platensis. • Above 25% defoliation applying treatments was always better than doing nothing. • Treatments can save more than 100 m3/ha and 1500 € ha−1 regardless of site quality. • Augmentative biological control surpasses chemicals for low-medium attack levels. • Chemical treatments were the best alternative under heavy defoliation attacks. Around 1.5 million ha of the Iberian Peninsula is currently occupied by Eucalyptus globulus , the preferred species for commercial plantations due to its fast growth and wood technological properties. However, these economically important plantations are being heavily damaged by Gonipterus platensis (Col: Curculionidae), an invasive species native to Australia which was established in the Peninsula, in the nineties. A classical biological control with the release of the egg parasitoid Anaphes nitens (Hym: Mymaridae) was launched in the Peninsula. Yet, in the colder regions, in the North of the Peninsula, the parasitoid is not efficient enough to control the weevil population. The resulting damage overcomes more than 200 million euros every year. Current control strategies rely on the application of insecticide (acetamiprid) or augmentative biological control (ABC) with yearly releases of A. nitens in spring. However, uncertainties about the best option persist. In this study, chemical and ABC treatments were submitted to a cost-benefit analysis with the aim of determining their viability against the weevil, based on a treatment efficacy and stand productivity trade-off analysis. A simulation tool (3-PG.d) was used to simulate the growth of E. globulus stands, under four defoliation intensity scenarios mimicking the removal of 25, 50, 75 and 100% of the spring new leaves biomass. Each defoliation scenario was combined with three treatments: (i) chemical (acetamiprid), (ii) ABC+ (optimistic approach), and (iii) ABC- (pessimistic approach). For each treatment, several plans of yearly treatments were tested. The Net Present Value (NPV) and the harvested volume were used to compare all treatment alternatives. The best treatment decision, based on a cost-benefit analysis comparing economic results and harvested volume, varied with the intensity of defoliation. Treating was always better than doing nothing, except for the 25% defoliation scenario. ABC+ offered the best economic results, relative to other treatments, for 25, 50 and 75% defoliation scenarios. ABC- was only as good as the chemical treatment for the 25 and 50% defoliations. Under the heaviest weevil attack (100%), applying insecticide was the best alternative, overcoming both ABC treatments. These results show that augmentative biological control was a strategy to consider for this study, and thus, may be a strategy to be considered in the future. The 3-PG.d simulator showed that it can be an asset for forest managers aiming at integrating chemical and/or biological treatments against forest pests in stand management decisions. [ABSTRACT FROM AUTHOR]

Abstract: Sustainable management of forest plantations and cost-effective control strategies depend on previous estimations of the economic level of damage caused by the pests. The eucalyptus weevil, a key pest of Eucalyptus plantations worldwide, is mainly controlled using classical biological control, using the mymarid egg-parasitoid Anaphes nitens (Girault). Nevertheless, in several temperate regions, the parasitoid fails to reduce the weevil populations to economically sustainable levels. This study attempts to (i) relate the efficiency of the parasitoid with climate variables, (ii) relate the level of damage caused by the weevil with the rate of parasitism, (iii) estimate the implications of weevil damage on wood production. Weevil density, damage caused by defoliation on the upper crown and parasitism rates were monitored in 2007, in 34 Eucalyptus globulus stands. Elevation, temperature and precipitation were assessed by using the Worldclim database. Using historic inventory data, wood production was projected to an age of 10years, prior to the arrival of the weevil, and compared with current data for the same stands. Parasitism rate by A. nitens was a key element explaining weevil density and tree defoliation, r 2 =0.37 and 0.41 (p <0.001), respectively. Significant relationships between parasitism rates and maximum temperature of the winter months (MaxTw), r 2 =0.55 and elevation r 2 =0.59 (p <0.001) were found. Other climatic variables, such as temperatures of the warmest months and precipitation, were not significantly related to parasitism rates. An upper threshold limit for the efficiency of the parasitoid appears for MaxTw of 10–11°C. The mean percentage of parasitism was low 10.1% (±4.9) for MaxTw below 10°C, increasing to 70.9% (±3.8) above 11.5°C. A reduction of the efficiency of A. nitens due to differences in the climatic niches of both the host and the parasitoid is hypothesised. The lower temperature threshold in particular, is of paramount importance for this host-parasitoid system. In consequence, in colder areas MaxTw<10°C, a defoliation of 74.1% was attained. Wood volume (projected to the age of 10years) was estimated to decrease to 51% in the affected areas in 2004–2006, compared to the previous period of 1995–1998. Estimated loss in wood volume increased exponentially reaching 43% and 86%, for 75% and 100% of tree defoliation, respectively. Therefore, considering the increase in the economic costs calculated for these regions, due to the high defoliation caused by the weevil, research into alternative control strategies is urgently needed. [Copyright &y& Elsevier]