Biology subjects

Dorais, M.

Publications and source records attributed to Dorais, M..

6 recordsLinked to original sources

bioRxiv2025

Consistent thrips biological control by Orius insidiosus on cucumber plants despite different LED lighting regimes

Artificial lighting, particularly light-emitting diodes (LEDs), is widely used in controlled- environment agriculture (CEA) to enhance crop productivity. Yet, light also acts as a sensory cue, directly and indirectly affecting insect pests and their natural enemies. Despite growing interest, the impacts of LEDs on multitrophic interactions remain poorly understood. This study assessed how spectral photoperiod extension modulates top-down effects (predator effects on pest densities, pest-related damage to plants, and plant defense-related gene expression) and bottom-up effects (plant morphology, light assimilation, and defense as well as growth hormone-related gene expression) in a tri-trophic system involving a plant, Cucumis sativus (greenhouse cucumber), a pest insect, Frankliniella occidentalis (western flower thrips), and a predator used for biological control, Orius insidiosus. Plants were exposed for two weeks to a 12-hour artificial sunlight simulating a cloudy winter day, with or without an 8-hour extension of blue, blue-red, or blue-green-red LEDs. Orius insidiosus reduced thrips populations by 96% {+/-} 9%, regardless of light treatment, and decreased foliar damage due to thrips by 46% on average. Predators produced offspring under all lighting conditions, although total numbers of O. insidiosus were lower under blue-green-red lighting. Pest densities remained similar across all light treatments, suggesting that light supplementation did not benefit F. occidentalis. Blue and blue-red spectra improved plant light assimilation, and photoperiod extension generally increased dry biomass (8% {+/-} 11%). Defense-related phytohormones were only marginally affected; surprisingly, some jasmonic acid pathway-related genes were upregulated in the presence of predators, suggesting additional plant-mediated effects. Our results underscore the potential of O. insidiosus to provide biological pest control services under artificial lighting regimes already used in crop production. Key MessageO_LILighting in agriculture alters dynamics of pest and beneficial insects C_LIO_LIWe asked how LED spectra influence net biological control outcomes in a tri-trophic system C_LIO_LIO. insidiosus reduced pest numbers by 96% and foliar damage by 46% C_LIO_LIPredators increased the expression of some jasmonic acid-related genes C_LIO_LIO. insidiosus showed potential for pest suppression under different lighting regimes C_LI

ecology↗

bioRxiv2025

Different artificial lighting spectra change the mating behavior of generalist predator Orius insidiosus (Say), and photoperiod extension promotes its development

In protected cropping systems such as greenhouses and indoor farming, augmentative biological control depends on release rates, establishment, and reproduction of natural enemies. Light-emitting diodes (LEDs) are widely used to enhance plant growth in these systems and are increasingly implemented in mass-rearing facilities for natural enemies. However, the impacts of LEDs on the life cycle of beneficial predators remain insufficiently explored. This study examined the mating behaviors and developmental performance of generalist predator Orius insidiosus under light spectra previously shown to support its predation of the pest thrips Frankliniella occidentalis. In laboratory experiments, predator pairs were exposed to artificial light sequences starting with a 12h base light condition simulating a cloudy winter day, supplemented by 8h photoperiod extensions (blue, blue-red, or blue-green-red spectra), and a control without extension. Mating occurred under all tested conditions, but blue light reduced mating probability, frequency, and duration. Photoperiod extension improved fecundity, fertility, and second-generation numbers of O. insidiosus adults, with blue light favoring egg laying and hatching but not metamorphosis into adults. The second-generation sex ratio was unaffected by light sequence, maintaining population viability with a balanced proportion of females. Our findings demonstrate that O. insidiosus can successfully mate, reproduce, and develop under artificial lighting and highlight the potential of modulating light spectrum to optimize both mass-rearing and establishment in protected crops. HighlightsO_LIPhotoperiod extension enhances development of the predatory bug O. insidiosus. C_LIO_LIBlue light reduces O. insidiosus mating probability, frequency, and duration. C_LIO_LIPhotoperiod extension with blue light favors O. insidiosus fertility and fecundity. C_LIO_LIOrius insidiosus sex ratio is unaffected by photoperiod. C_LIO_LILEDs could enhance natural enemy establishment in protected crops. C_LI

animal behavior and cognition↗

bioRxiv2024

Artificial lighting affects the predation performance of the predatory bug Orius insidiosus (Say) against the Western flower thrips Frankliniella occidentalis (Pergande)

Protected crops, such as greenhouses and indoor farming environments, using light-emitting diodes (LEDs) enable the modulation of the light spectrum, intensity, and photoperiod for agronomic purposes. This creates dynamic artificial light conditions for insects and arachnids, including predators used in biological control. Despite increasing interest, the effects of LEDs on predator behavior and control performance remain poorly understood. In the laboratory, we examined the locomotion and predation behaviors of the generalist predator Orius insidiosus against the pest Frankliniella occidentalis under various light spectra and intensities. We tested narrowband blue, green, and red spectra, three ratios of red and blue light, and a spectrum combining all three colors across a gradient of light intensity in microcosms. Orius insidiosus was active and successfully attacked prey under all lighting conditions, with 70% of individuals engaging in predation during the observation period. The light spectrum significantly influenced all recorded behaviors, while light intensity had negligible effects. Narrowband spectra led to the highest attack probabilities, but the mixed blue-red spectrum with a higher proportion of red light yielded the highest prey capture rates. The spectrum with all three colors showed intermediate capture success. These trends were consistent regarding capture probability in more complex environments with cucumber plants, where thrips were exposed to 24-hour artificial light sequences before and during predator releases. However, thrips survival rates remained similar across all lighting treatments. Our results demonstrated that while lighting treatments affect predator behavior, Orius insidiosus retains its ability to capture prey under various light conditions. This paves the way for developing lighting strategies that balance plant productivity with effective biological control in protected crop environments.

animal behavior and cognition↗

bioRxiv2023

Forest tree extracts induce resistance to Pseudomonas syringae pv. tomato in Arabidopsis

BackgroundThe widespread use of conventional pesticides to control plant fungal and bacterial pathogens poses significant risks to human health and the environment, and there is an urgent need for safer and more sustainable alternatives in agricultural management. Studies have shown that plant extracts can be effective in controlling plant diseases either by directly targeting the pathogens or by reinforcing the host plants own defenses. Here, we examined the potential of ethanolic extracts from forest tree species eastern hemlock, English oak, eastern red cedar and red pine for their antibacterial activity against Pseudomonas syringae pv. tomato (Pst) strain DC3000 and the ability of these forestry by-products to trigger effective defense responses in the model plant Arabidopsis thaliana. ResultsThe four tree extracts exhibited direct toxic effects against Pst DC3000, as notably observed for the English oak extract inhibiting bacterial growth and showing bactericidal activity at relatively low concentrations. Using an Arabidopsis line expressing reporter protein {beta}-glucuronidase under the control of a salicylic acid-inducible pathogenesis-related protein gene promoter, the extracts were shown also to induce defense-related genes expression in leaf tissue. RT-qPCR assays with DNA primers for different gene markers further confirmed this conclusion and highlighted gene-inducing effects for the tree extracts triggering, at different rates, the expression of salicylic acid- and oxidative stress-responsive genes. The extracts direct antibacterial effects, combined with their defense gene-inducing effects in planta, resulted in a strong host plant-protecting effect against Pst DC3000 associated with bacterial growth rates reduced by [~]75 to 98% seven days post-infection, depending on the extract. ConclusionsThese findings show the effectiveness of tree extracts as eventual plant protectants against the plant bacterial pathogen Pst. In a broader perspective, they suggest the potential of these forestry by-products as a source of bioactive compounds useful in plant protection and as a sustainable, eco-friendly alternative to conventional synthetic pesticides for the management of economically important plant pathogens.

plant biology↗

bioRxiv2023

Supplemental LED lighting improves plant growth without affecting biological control in a tri-trophic greenhouse system

Artificial lighting, including light-emitting diode (LED) illumination, is increasingly being optimized in protected agricultural systems to maximize plant yield and quality. However, it may also cause other top-down and bottom-up effects in these relatively simple ecological communities that also include insect pests and their natural enemies. While some effects of LED lighting on insects have been demonstrated to date, it is not known how they influence biological control of insect pests in practice. To examine potential top-down and bottom-up impacts of LED illumination on greenhouse biological control with parasitoids, we studied the effects of artificially lengthened days on a tri-trophic system in cages and in a greenhouse. We grew plants under a 12-hour photoperiod of white-supplemented light with 6 hours of additional 1) white light or 2) red and blue light, or 3) with no additional light. We exposed the plants to the pest aphid Myzus persicae (Hemiptera : Aphididae) with or without its parasitoid wasp Aphidius matricariae (Hymenoptera : Braconidae), or to no insects. The 18-hour light treatments increased mean plant dry mass by 127% compared with the 12-hour control without affecting the aphids population density or the parasitoids biological control efficacy under relatively low light conditions. This suggests that insect communities in protected agriculture can be resilient to even drastic changes in their light environment, and that adjusting crop lighting in a manner that affects plant growth does not necessarily compromise biological controls effectiveness.

ecology↗

bioRxiv2023

The effects of LED daylength extensions on the fecundity of the pest aphid Myzus persicae and the daily activity patterns of its parasitoid, Aphidius matricariae

Supplemental lighting, such as with LED lamps, allows greenhouse producers to maintain yields when natural light levels are low. Since both insect pests and their natural enemies are sensitive to light, both the duration and spectrum of LED daylength extensions could affect biological pest control in greenhouses. Longer days could allow for extended periods of reproduction for pests or foraging activity of biological control agents, possibly depending on the spectra used for these extensions. However, the effects of lengthening days with different LED spectra on the behaviour of biological control agents has mostly been studied in short-term experiments to date, and has not always included the context of the lights effect on their hosts reproduction. In growth chambers, we examined the locomotor activity of the parasitoid biocontrol agent Aphidius matricariae (Hymenoptera : Braconidae) as a predictor for foraging activity and the fecundity of its aphid host Myzus persicae (Hemiptera : Aphididae) over multiple days under different daylength extension regimes representative of those used in greenhouse vegetable production. We compared the effects of 14, 16, 18, and 20 h photoperiods, and 12 h days extended by 6 h with three different spectral qualities. The parasitoids adjusted how their activity was distributed throughout the lit period of the day (i.e., its total duration and peak timing) without changing the total amount of daily activity, regardless of the photoperiod or the light spectrum used for daylength extension. The aphids peak fecundity was not affected by photoperiod or spectral quality. Our results suggest that at least some behavioral and reproductive traits of these insects can be resilient to even drastic changes in their light environment.

ecology↗