First report of the establishment of the biocontrol agent Trichilogaster acaciaelongifoliae in Portugal
Acacia longifolia (Fabaceae) is native to Australia and was introduced into Europe between the late 19th and early 20th centuries. Since its introduction in Portugal, the species has become one of the most widespread invasive species. In Portugal, its forms 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.
Due to similar negative impacts recorded throughout its introduced range, the species has been the target for classical biological control. In South Africa, A. longifolia has been successfully controlled over the last 30 years using the bud-galling wasp Trichilogaster acaciaelongifoliae (Hymenoptera: Pteromalidae). In Portugal, T. acaciaelongifoliae was released in 8 sites along the Portuguese coast in 2015 following extensive research to ensure host specificity. Over 450 female wasps were released onto 150 trees. During the post-release monitoring at the release sites in April-July 2016, 56 galls were detected on 11 trees spread over 4 sites. During this phase of monitoring, all galls were still intact with no emergence holes. During a second monitoring phase (July and August 2016), the previously observed galls had changed their appearance, starting to desiccate and shrivel with some already turning brown, and some with emergence holes. In January 2017, immature second generation galls were observed. Compared to the southern hemisphere,
T. acaciaelongifoliae, completes its life cycle quicker in Portugal, where it takes just 8-9 months compared to 12 months in South Africa. Although the number of galls is currently low, it is encouraging that the population is showing signs establishment at the release sites and T. acaciaelongifoliae is adjusting its life cycle to the northern hemisphere season.
T. acaciaelongifoliae, completes its life cycle quicker in Portugal, where it takes just 8-9 months compared to 12 months in South Africa. Although the number of galls is currently low, it is encouraging that the population is showing signs establishment at the release sites and T. acaciaelongifoliae is adjusting its life cycle to the northern hemisphere season.
Sources
Marchante H, López-Núñez FA, Freitas H, Hoffmann JH, Impson F, Marchante E (2017) First report of the establishment of the biocontrol agent Trichilogaster acaciaelongifoliae for control of invasive Acacia longifolia in Portugal. EPPO Bulletin, DOI: 10.1111/epp.12373.