Unexpected Ecological Effects of Distributing the Exotic Weevil, <i>Larinus planus</i> (F.), for the Biological Control of Canada Thistle
Bibliographic record
Abstract
Abstract: Rhinocyllus conicus , a weevil introduced for biological control of exotic weeds, has had major nontarget ecological effects on native thistles. Some practitioners have argued that this is an isolated case. We report, however, that another Eurasian weevil ( Larinus planus ), currently being distributed in North America for the control of Canada thistle ( Cirsium arvense ), is significantly reducing seed production by a native thistle ( Tracy's thistle, Cirsium undulatum var. tracyi ) in Colorado. In 1999 we discovered L. planus feeding in flower heads of Tracy's thistle near a 1992–1993 biocontrol release site. Of the heads collected, 74% had evidence of L. planus , and these heads produced only 1.1 viable seeds on average, compared with 45.9 in heads without this weevil. In 2000 we investigated whether L. planus feeding persisted on Tracy's thistle and whether this feeding affected seed production significantly. Feeding by L. planus occurred on 80% of the plants and in 76% of all the main heads of Tracy's thistle. Flower heads with L. planus averaged 1.4 viable seeds, compared with 44.5 in uninfested heads. Feeding by L. planus decreased the average number of viable seeds produced per plant by over 51%. In contrast, L. planus had less effect on its targeted exotic host, Canada thistle than it did on Tracy's thistle. The high‐frequency and high‐level feeding of L. planus on the native species, coupled with the lack of evidence of its effectively limiting the seed production or density of Canada thistle suggest that the deliberate distribution of this weevil entails a high risk‐to‐benefit ratio and should be discontinued. Our findings challenge the general assumption that biological control with exotic insects is consistent with conservation goals of weed management in natural areas. Effective, a priori quantitative evaluation of the potential effects on both target and nontarget species and better regulatory oversight are required.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".