Effects of ground predators, abiotic factors and plant density on the flea beetles, Phyllotreta cruciferae (Goeze) and Phyllotreta striolata (F.) (Coleoptera: Chrysomelidae)
Bibliographic record
Abstract
The crucifer flea beetle, Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae), and the striped flea beetle, Phyllotreta striolata (Fabricius) (Coleoptera: Chrysomelidae), are prominent economic pests to canola crops, Brassica napus, (L.) (Brassicaceae) in the Canadian prairies, by defoliating canola seedlings, resulting in recurring yield losses. Current management strategies in the Canadian prairies rely heavily on chemical control via both seed-coated and foliar spray treatments. To limit chemical pesticide applications due to potential adverse environmental effects, there has been a focus on alternative flea beetle management strategies including altering plant density and determining potential natural enemies. In addition, few studies have demonstrated how temperature and plant density affect flea beetle feeding and there is little known about the factors affecting stem feeding on canola seedlings. Laboratory studies in petri dishes and microcosms were completed to examine effects of temperature, plant density and predators on cotyledon and stem feeding by both species of flea beetles in terms of damage intensity and prevalence. Both species defoliated similar amounts, suggesting no feeding difference in species. Feeding increased with temperature and more defoliation occurred on the underside of the cotyledons. Pterostichus melanarius and Pardosa spp. reduced flea beetle abundances as well as total cotyledon defoliation. In addition, there was less cotyledon and stem damage at higher plant densities. Field studies were completed in four regions of the Canadian prairies (Lethbridge and Peace River, AB; Saskatoon, SK; and Carman, MB) over 4 years (2018 – 2021). Evidence of both the resource concentration hypotheses and a dilution effect was found as flea beetle abundance increased with plant density, yet defoliation levels generally decreased. Yield increased with plant density regardless of the management treatment or region. The knowledge gained on how flea beetles’ feeding on stems and cotyledons is affected by temperature, plant density, and predators will help for in-field scouting and assessment ratings and provide information for future research into biological control potential with the tested predators. In addition, using plant density as a flea beetle management strategy either combined with current chemical practices or as an alternative, is effective to protect yield while limiting chemical applications.
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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 | 0.001 |
| 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".