Influence of Biocontrol Insects onCanada Thistle: Seed Production,Germinability, and Viability
Bibliographic record
Abstract
We conducted surveys of thistle-feeding insects on Canada thistle [Cirsium arvense (L.) Scop.] during the 2000 and 2001 growing seasons at Lacreek National Wildlife Refuge (LNWR), South Dakota, and analyzed their impact on thistle seed production, germination, and viability. Insects included Canada thistle stem weevil [Hadroplontus litura, formerly Ceurtorhynchus lilura, (Coleoptera: Curculionidae)], introduced at LNWR as a biocontrol agent, plus two seed head parasites, the thistle head weevil [Rhinocyllus conicus (Coleoptera: Curculionidae)] and the seed head fly [Terellia ruficauda (Diptera: Tephritidae)]. Infestation by these insects caused no significant reduction in per-head seed yield, with means ranging from 82.5 seeds per head, when both Canada thistle stem weevil and seed head parasite( s) were present, to 85.7 seeds per head with no parasites present. Average per-head seed yield was found to decline from 86.3 to 81.3 between our 12 to 14 July 2000 and 26 to 27 July 2000 sampling periods, but the decline was not attributable to seed head parasites. Infestation by seed head fly occurred at a rate of 14.7% of open female heads; male heads were not attacked by seed head fly. Thistle head weevil infested both female and male heads with 10.8% of female heads in pre-flowering condition infested compared to 7.8% in flowering or postflowering stage; about 7% of male heads were infested in both pre-flowering and flowering/post-flowering stages. Germination testing suggested some reduction in germination rates due to seed head parasites, but high variability among replicates often obscured the source of differences. Seed viability, as revealed by germination and tetrazolium testing, was reduced by about 2% by either seed head parasite and by about 4% when both the seed head fly and thistle head weevil were present. The impact of these insects on the potential for Canada thistle to spread by seed appeared to be negligible.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".