Home / Science / Biological Control Gone Wrong: Weevil Targets Natives
Biological Control Gone Wrong: Weevil Targets Natives
19 Aug
Summary
- A biological control program meant to curb invasive thistles backfired.
- The introduced thistle seedhead weevil began feeding on native thistles.
- This unintended impact threatened endangered native plant species.
A biological control initiative launched in the United States between 1969 and 1972 aimed to manage invasive thistles. The strategy involved introducing the thistle seedhead weevil, Rhinocyllus conicus, from Europe. This insect was intended to weaken invasive plants by attacking their reproductive structures, thereby reducing seed production.
However, after establishing itself, the weevil began targeting native thistles, including species from the Cirsium genus. This unforeseen behavior presented a significant problem as native thistles play a role in their ecosystems. The problem was exacerbated for rare and endangered native thistles, such as the Sacramento Mountain thistle.
The weevil's impact on native species, particularly on seed production, could critically affect already vulnerable populations. Reversing such introductions is exceptionally difficult once the organism has dispersed and become established in the environment.
Consequently, interstate shipments of the thistle seedhead weevil are now prohibited by the USDA. This situation serves as a critical lesson in invasive species management, emphasizing the need for thorough ecological evaluations to prevent unintended harm to native biodiversity.
