Suppression of seed production as a long-term strategy in weed biological control: The combined impact of two biocontrol agents on Acacia mearnsii in South Africa

Background

Acacia mearnsii is a woody plant native to Southeastern Australia and Tasmania. Introduced into South Africa in the mid-1800s for timber, the species has become invasive to the region. Reducing the amount of precipitation reaching the ground, hindering agriculture and lowering biodiversity are just a few of the detrimental impacts. Though there has been pushback to controlling this species for commercial interests, two biological control agents, a seed-feeding weevil and a flower-galling midge are known to control species spread and are introduced to the region.

Goals and Methods

This study is conducted in the Western and Eastern Cape Provinces of South Africa. The authors determine if using these two control agents are effective at controlling the seed production and spread of Acacia mearnsii. The authors use seed traps in several sites, collecting and monitoring the seed rain for evidence of insect impact. This study was conducted over five years to assess a longer-term impact of the control agents.

Conclusions and Takeaways

Overall, the authors determine that the use of biological control agents (insects) can be highly effective at reducing seed production in A. mearnsii. These controls both reduce production and seed bank density of A. mearnsii seeds. In combination with other control methods such as mechanical removal and herbicide, overall species control looks possible.