Biological control of Acacia longifolia in Portugal
Acacia longifolia (Fabaceae) is a small shrub or tree species native to South-Eastern Australia. It is invasive in a number or countries including Argentina, Brazil, New Zealand and South Africa. Within the EPPO region it is considered invasive in Spain and Portugal where it can form extensive populations within coastal ecosystems which act to displace native plant communities. A. longifolia alters soil chemistry, reduces forest productivity, and increases the potential for natural fires. In Portugal, the gall forming wasp Trichilogaster acaciaelongifoliae (Hymenoptera: Pteromalidae) was released as a biocontrol agent in 2015. Since then, and up to 2020, the establishment, spread and impact of the biocontrol agent has been monitored across 61 sites. Since its first release, establishment has been confirmed at 36 sites. The transfer of the wasp from the southern hemisphere limited its initial establishment, but increased rates of establishment followed with synchronization of its life cycle to northern hemisphere conditions. T. acaciaelongifoliae populations then experienced an exponential growth (from 66 galls by 2016, to 24 000 galls by 2018). Galled A. longifolia branches produced significantly fewer pods (-84.1%), seeds (-95.2%) and secondary branches (-33.3%). The results are promising for the long-term effectiveness of this biocontrol agent and are also encouraging for future biocontrol programmes that require hemisphere translocations of biocontrol agents.
Sources
López-Núñez FA, Marchante E, Heleno R, Duarte LN, Palhas J, Impson F, Freitas H, Marchante H (2021) Establishment, spread and early impacts of the first biocontrol agent against an invasive plant in continental Europe. Journal of Environmental Management. https://doi.org/10.1016/j.jenvman.2021.112545