Biology subjects

Bush-Beaupre, A.

Publications and source records attributed to Bush-Beaupre, A..

5 recordsLinked to original sources

bioRxiv2026

Who, what, when, where: Phenological trends of the Seedcorn Maggot Complex (Diptera: Anthomyiidae) in three vegetable crops in Southern Quebec

In eastern Canada, the seedcorn maggot complex (SMC) includes three agriculturally important taxa: Delia platura biotypes H and N, and D. florilega. Because their larvae are morphologically indistinguishable, field-collected individuals are often grouped together despite differences in phenology and life history. Using larval collections from broccoli, green onion, and dry onion fields in Southern Quebec (2017-2022), we identified specimens via HRM analysis and characterized taxon-specific phenology and abundance using Bayesian hierarchical generalized additive models. In Allium crops, D. platura biotype N dominated early-season infestations (May), followed by a shift in early June towards increased abundance of biotype H and D. florilega. In broccoli, all SMC members appeared later, with overlapping abundance peaks in June. These results reveal strong crop-dependent phenological differences and underscore the need to treat SMC members as distinct biological entities in pest management. The implications for optimizing an emerging sterile insect technique (SIT) program for D. platura in Quebec are significant: field releases of sterile males should target early-season biotype N in Allium crops, followed by releases of both biotypes later in the season in broccoli to maximize control efficacy.

ecology↗

bioRxiv2026

Extending the causal inference toolkit for ecologists: A visualization method of indirect effects

Much ecological research focuses on phenomena where a given variable can affect another either directly or indirectly through the effect of one or more intervening variables. While various methods to quantify the magnitude of these effects are available, they can be difficult to interpret in a meaningful way, especially for indirect effects. Studies thus often quantity direct effects and infer indirect ones more or less formally. We propose a method for visualizing indirect effects by means of plotting model predictions of an outcome in the presence of both exposure and mediator variables. We demonstrate the method through simulations and apply them to a real-world example involving Tree Swallows (Tachycineta bicolor) and their obligatory hematophagous ectoparasites, Protocalliphora bird blowflies (Diptera: Calliphoridae). Our procedure, which can be seamlessly integrated into an analysts workflow using commonplace software, should prove instrumental to disentangle and interpret relationships among variables involved in ecological mechanisms.

ecology↗

bioRxiv2026

Enemy mitigation in farmlands: Agricultural intensification negatively impacts avian nesting and subsequent ectoparasite infestation

Intensive agricultural practices directly affect farmland bird and non-target insect populations by modifying their habitats, but may also act indirectly by altering their interactions. Notably, the breeding success of insectivorous birds has been shown to suffer from reduced prey availability. Yet little is known about how agriculture influences host-parasite relationships in wild birds. How agricultural intensity affects parasites, and whether this alleviates or exacerbates the trophic stress imposed on birds therefore remains to be determined. We estimated the number of obligate hematophagous Protocalliphora blowfly larva (Diptera: Calliphoridae) that parasitized nestlings in 2,560 Tree Swallow (Tachycineta bicolor) broods along a 10,200-km{superscript 2} gradient of agricultural intensity between 2004 and 2019 in Quebec, Canada. We first modeled two key variables along the causal paths expected to affect Protocalliphora prevalence and load (abundance) within infested broods: nestling hatching date and nestling host availability. Hatching phenology varied by several days with early-spring meteorological conditions and parental age, as for nestling availability (nestling-days), which also decreased along the agriculture intensity gradient as pastures and hay fields were replaced by large-scale, cereal row crops. Nestling availability peaked under low precipitation rates when temperatures reached 18 to 25 {degrees}C. Prevalence and load of blowfly larvae directly increased with nestling availability as well as with the temperature and precipitation that occurred during the larval development and pupation stages. Controlling for nestling availability, Protocalliphora prevalence and load peaked in forested landscapes interspersed by pastures and hay fields and reached their lowest in landscapes dominated by corn and soybean monocultures with minimal tree cover. Agricultural intensity thus reduced infestation likelihood and severity both directly and indirectly, by limiting nestling host availability. This finding is notable given the documented negative effects of agricultural intensity on fledgling number and body condition in farmland birds, even after controlling for insect prey reduction. If agricultural intensity indeed reduces the parasitic pressure exerted by bird blowflies and its consequences for fledgling condition and recruitment, this suggests that other agricultural impacts (e.g., toxicological effects from pesticides) may play a larger role than previously recognized in the severe declines of farmland bird populations observed across the Holarctic. Open research statementThe data supporting this study are not yet publicly available, as they require final harmonization, documentation and anonymization prior to archiving. Upon acceptance of the manuscript, all underlying data and associated code will be permanently deposited in the Zenodo repository and made fully accessible with a DOI.

ecology↗

bioRxiv2025

Sterile insect technique reduces cabbage maggot (Diptera: Anthomyiidae) infestation in root crucifers in Canada

The cabbage maggot (Delia radicum Linnaeus) is a major pest of brassica vegetables in Canada that has traditionally been managed with soil-applied insecticides. However, recent regulatory restrictions on key products such as chlorpyrifos have created a pressing need for alternative solutions. This study evaluates the sterile insect technique (SIT) as a control method for the cabbage maggot in root crucifers. Large-scale field trials conducted from 2019 to 2022 in Quebec (Canada) demonstrated significant reductions in D. radicum infestations in radish and daikon crops. Quality control measures confirmed the effectiveness of sterilization, with minimal impact on male performance. The results suggest that the SIT is a promising, environmentally friendly alternative to chemical control for cabbage maggot management. The study further highlights the importance of optimizing release strategies and improving predictive models to guide deployment. Overall, the SIT offers growers a viable option to reduce reliance on insecticides while maintaining crop health and yield.

ecology↗

bioRxiv2023

REPRODUCTIVE COMPATIBILITY OF TWO LINES OF DELIA PLATURA (DIPTERA: ANTHOMYIIDAE)

Accurate identification of agricultural pests is a major component of integrated pest management. The seedcorn maggot, Delia platura (Diptera: Anthomyiidae), is a cosmopolitan polyphagous pest species which may be found in high numbers in numerous crops. Two morphologically identical genetic lines of D. platura (H- and N- lines) with distinct distributions were recently identified. However, no study to date has investigated the reproductive compatibility of the two lines and thus the possibility that they may actually be two unique biological entities. A previous study described the reproductive traits of the two lines and suggested that H-line females are highly selective towards the male with which they mate, pointing to a possible pre-mating isolation mechanism between the lines. Using laboratory-reared colonies originating from the Monteregie region in Quebec, this study investigates the reproductive compatibility of the two D. platura lines. We found that only one of thirty H-line females was inseminated by an N-line male, further suggesting mate choice as a pre-mating isolation mechanism between the lines. However, N-line females were readily inseminated by H-line males, suggesting a lack of pre-mating isolation in this type of cross. The eggs laid by N-line females mated with H-line males had a lower hatching rate than the ones laid by females of intra-line crosses suggesting either post-mating pre-zygotic or post-zygotic partial isolation. However, the larvae that did hatch had a comparable developmental success to those from intra-line crosses in terms of survival and developmental time from larval hatching to adult emergence, pupal weight, and adult sex ratio, suggesting a lack of post-zygotic isolation for these life stages. Considering the different biological traits of the two lines, we suggest the use of the biotype terminology to designate the two biological entities and discuss their implications for integrated pest management.

ecology↗