Australian insect reduces ‘Acacia longifolia’ seed production by up to 98% in Portuguese coastal dunes
The study found that the increase in galls formed by the tiny bud-galling wasp led to a significant reduction in pods and seed rain, preventing the replenishment of the soil seed bank – one of the main mechanisms that enable the persistence of this invasive species.
A research team from the Department of Life Sciences (DCV) of the Faculty of Sciences and Technology, University of Coimbra (FCTUC), and from the Coimbra Agriculture School (ESAC/IPC) has validated the effectiveness of biological control methods for Acacia longifolia, also known as the long-leaved wattle, one of the most problematic invasive plants along the Portuguese coast.
The Australian bud-galling wasp Trichilogaster acaciaelongifoliae, introduced in 2015 after several pre-release tests and risk analyses, is reducing the annual seed production of this invasive plant by up to 98% in some areas, proving to be an effective, safe, and sustainable tool to support the recovery of dune ecosystems.
“Our findings show that biological control is effective, reducing seed rain by up to 98% after five years.”
After nine years, seed production has virtually disappeared in areas where the agent has been established the longest,” explains the study’s first author, Liliana Neto Duarte, researcher at the Centre for Functional Ecology (CFE) and at the Research Centre for Natural Resources, Environment and Society (CERNAS/ESAC/IPC).
“This is a crucial step towards limiting the growth and reproduction of Acacia longifolia and enabling the regeneration of native dune vegetation,” says Elizabete Marchante, a researcher at CFE/FCTUC. "These scientific findings have now been published in the Journal of Environmental Management,” she adds.
According to the study, which monitored A. longifolia trees over six years in several dune ecosystems of the Central region, the increase in galls formed by the insect has led to a drastic decline in pod and seed production, preventing the replenishment of the soil seed bank – one of the main mechanisms ensuring the persistence of this invasive species.
Additionally, the researchers observed the progressive weakening of some trees under heavy gall pressure, which, in some cases, may lead to their death. The authors also note that biological control should be integrated with other control practices, such as mechanical cutting, and keeping galled trees in intervention areas, to ensure long-term control continuity.
“The success achieved reinforces the need to invest in integrated strategies for managing invasive species in Europe, taking advantage of natural solutions that reduce costs and increase efficiency,” the researchers conclude.
The scientific paper “Biocontrol in action: Assessing the impact of a biocontrol agent on invasive plant seed dynamics” is available here.