Liliana Duarte1, Hélia Marchante1, Francisco A. López-Núñez2, Jael Palhas2, Olímpia Sobral1, Marília Claro1 and Elizabete Marchante2
1Instituto Politécnico de Coimbra, Escola Superior Agrária, Centre for Functional Ecology – Science for people and the planet, Bencanta, 3045-601, Coimbra, Portugal
2Centre for Functional Ecology, Department of Life Sciences, University of Coimbra. Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
Successful management of plant invasions is frequently difficult to attain and entail prohibitive costs. A combination of methodologies, persistence and adaptive management, may improve chances against invasive alien plants (IAP). Acacia longifolia, Acacia dealbata and Acacia melanoxylon are worldwide invaders and are amongst the most widespread IAP in Portugal, causing diverse negative impacts that turn them into transformer species. Managers usually cut them, even though this is not the most effective technique, resulting in low levels of success. GANHA (Sustainable management of Acacia spp: an applied perspective of natural control and other methodologies to improve habitat recovery in protected areas; POSEUR-03-2215-FC-000052) is an applied project focused on the integration of different techniques to control A. longifolia, A. dealbata and A. melanoxylon in Natura 2000 sites and protected areas. The added value of the project is based on (i) the use of the Australian bud-galling wasp (Trichilogaster acaciaelongifoliae), the first biocontrol agent (BCA) released in Portugal (November 2015) to control A. longifolia, to reduce seed formation; (ii) the selection of the most effective techniques according to each species characteristics; (iii) the persistence of follow up treatments; and (iv) the close collaboration amongst operational staff, managers and academics in an adaptive management approach.
The main goals are to (i) reduce the seed bank of A. longifolia, by the release of Trichilogaster acaciaelongifoliae; (ii) reduce the areas currently invaded by A. longifolia, A. dealbata and A. melanoxylon through physical techniques (i.e. hand pull, cut and/ or debarking), and/ or combined with chemical methods; (iii) start testing the specificity of two new biocontrol agents, in quarantine, targeting the reduction of A. dealbata and A. melanoxylon seed production; and (iv) increase awareness of IAP amongst the population of the project intervention areas.
In June – July 2018 the BCA release was made, for the first time, exclusively with wasps of Portuguese origin. Preliminary results indicate new sites with galls in early 2019, with apparent higher abundances than the first generation of South African wasps detected in 2016. Initial controls and a first follow up treatment with physical and/or chemical techniques have been completed in most of the areas, debarked A. dealbata and A. melanoxylon trees are dying and other follow ups are planned. The persistence of follow up treatments is expected to contribute in achieving higher success in IAP control but operational difficulties and dealing with limitations imposed by managers can be challenging and will be discussed.