Population-level impact of egg parasitism on Halyomorpha halys despite a rapid shift in parasitoid species composition
Bibliographic record
Abstract
Abstract Intentional introductions of the egg parasitoid Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) have been carried out in Italy since 2020 for the control of the invasive Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), with releases conducted along ecological corridors of untreated vegetation. These introductions took place in an area where unintentionally introduced populations of Trissolcus mitsukurii (Ashmead) (Hymenoptera: Scelionidae) were already present and adventive populations of T. japonicus were just beginning to establish. In this study, we investigated whether T. japonicus releases contributed to the impact of egg parasitism on H. halys populations, and what the total impact of egg parasitism on pest population growth was over four growing seasons (2020–2023) in ten kiwifruit orchards in Italy. Although higher parasitism by T. japonicus was observed in orchards adjacent to release sites, the total impact of egg parasitism on H. halys remained similar over the four years because an increasing prevalence of T. japonicus over the study period was strongly associated with a corresponding decrease in egg parasitism by T. mitsukurii . Using a parameterized stage-structured matrix model, we estimate that the joint action of T. mitsukurii and T. japonicus (average total egg parasitism: 33–39%) prevented an expected 18–29% increase in net reproductive rate ( R 0 ) of H. halys over the four years of the study. This analysis suggests that irrespective of year-to-year temperature variation favoring pest reproduction and the displacement of T. mitsukurii by T. japonicus (hastened by releases), egg parasitism has been playing an important and consistent role in the biological control of H. halys .
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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".