# US thistle-control weevil attacked endangered native plants

2026-08-19T11:24:16+00:00 | Health & Science | Indian Opinion Desk

Corroboration: 1 independent outlet

The United States released the European thistle seedhead weevil, Rhinocyllus conicus, between 1969 and 1972 to control invasive musk thistle and reduce its seed production. The insect’s larvae feed inside flower heads, damaging developing seeds and limiting reproduction. After spreading beyond release areas, the weevil also attacked native Cirsium thistles. The USDA Forest Service identified the endangered Sacramento Mountain thistle in southern New Mexico among the affected species. Research found the insect feeding on at least 25 native Cirsium species and completing its development on two in controlled conditions. The case shows how biological control agents can affect non-target plants after release.

## Indian Opinion Analysis

Biological control programmes depend on selecting an organism whose feeding is narrow enough to avoid native species. Host-range testing can reduce this risk, but behaviour may change once an agent encounters new plants across a larger ecosystem. Post-release monitoring is therefore needed to detect non-target impacts and guide containment or further management. The key signal is whether affected native thistle populations continue producing enough viable seed to maintain themselves.

## Coverage

- timesofindia.indiatimes.com <https://timesofindia.indiatimes.com/science/between-1969-and-1972-the-us-released-a-european-weevil-to-fight-invasive-musk-thistle-it-later-attacked-at-least-25-native-thistles-including-rare-and-endangered-species/articleshow/133342649.cms>
  Explains intended control and ecological consequences without overt editorial judgement

This story was synthesised by AI from the source linked above.

Tags: Rhinocyllus conicus, United States, USDA Forest Service
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