2025 Agenda & Program

GP1: Enhancing greenhouse crop resilience: Sustainable strategies for aphid control using integrated pest management

A. Sulthana (1), R. Labbe (2) S. VanLaerhoven (2)

(1) University of Windsor, Windsor, ON

(2)Agriculture and Agri-Food Canada, Harrow, ON

The greenhouse industry is vital to Canada’s agriculture, enabling year-round production of key crops like tomatoes, cucumbers, and peppers. However, aphids like Green Peach Aphid, Melon Aphid, and Potato Aphid pose serious threats by feeding on plants and transmitting viral diseases, causing economic losses. Chemical insecticides, traditionally used for aphid control, face challenges such as resistance development and environmental risks, necessitating sustainable alternatives. This research focuses on Integrated Pest Management (IPM) by evaluating biological control agents (BCAs), like predators and parasitoids, alongside insecticides to optimize aphid control. It also investigates the genetic basis of aphid resistance to improve management strategies. Key hypotheses tested include: (1) insecticides differ in their effectiveness against aphids; (2) systemic insecticides contaminate aphid honeydew, harming BCAs through prolonged exposure, while direct insecticide contact can reduce BCA survival and reproduction; (3) syrphid flies, promising yet underused aphid predators, vary in predation efficiency and greenhouse persistence; and (4) regional genetic variation in aphids influences insecticide susceptibility and resistance development. Using field trials, greenhouse experiments, and molecular tools like DNA barcoding and SNP assays, the study will assess BCAs' performance and monitor aphid resistance. The integrated findings aim to enhance IPM by combining chemical and biological methods, reducing crop damage and chemical reliance. Ultimately, this supports more productive, profitable, and environmentally sustainable Canadian greenhouse operations that meet consumer demands for safer produce.

GP2: Rhizosphere microbiome responses to clubroot infection in canola

M. Campbell (1), B. Gossen (2), and M.R. McDonald (1)

(1) Department of Plant Agriculture, University of Guelph, Guelph, ON

(2) Agriculture and Agri-Food Canada, Saskatoon, SK

Canola (Brassica napus L.) is the most extensively grown oilseed crop in Canada, with nearly 9 million hectares seeded in 2024, contributing over $43 billion to the national economy. The canola rhizosphere hosts a complex and dynamic microbial community composed of fungi, bacteria, and oomycetes, which may protect against soil-borne pathogens. An important disease of canola is clubroot, caused by Plasmodiophora brassicae Woronin, an obligate biotrophic Chromist. The pathogen infects canola roots, producing characteristic clubbing that reduces water and nutrient uptake. Infection ultimately leads to stunted growth, wilting, and in severe cases, plant death. In this study, microbial communities in the rhizosphere of clubroot-infected and non-infected canola plants were compared with those in bulk soil from the same field. Soil samples were collected from 10 fields in the northern Ontario Temiskaming Shores district in September 2024. Rhizosphere soil was extracted using phosphate-buffered saline and metabarcoding was conducted using universal primers targeting 16S rRNA (bacteria and archaea), ITS (fungi), and 18S rRNA (oomycetes) to identify organisms to the genus level. Bulk soil exhibited the highest richness and Shannon diversity of fungi, but the lowest richness and diversity of bacteria. Rhizosphere soil from clubbed roots showed the greatest richness and diversity of oomycetes. There were no differences in beta diversity, assessed using Bray–Curtis dissimilarity, within fungal, bacterial, or oomycete communities for any sample type. This study provides baseline information on the microbiome of soils associated with clubroot.  Studies are ongoing to determine how clubroot influences the canola rhizosphere complex.

GP3: Quantifying the effect of the herbivory-induced plant volatile, (Z)-3-hexenyl propanoate, on Thrips parvispinus host plant-seeking behaviours in Canadian greenhouse crops

A. Johnson (1,2), R. Labbe (1,2), R. Hallett (2)

 (1) Agriculture and Agri-Food Canada, Harrow, ON

(2) Department of Environmental Science, University of Guelph, Guelph, ON

Thrips parvispinus (Karny) (Thysanoptera: Thripidae) is a polyphagous pest native to Asia. It causes both direct damage through feeding and indirect damage by transmitting plant diseases. Although not established in Canada, it can be intercepted on imported plant materials. Herbivory-Induced Plant Volatiles (HIPVs) have shown promise as repellents for related thrips species. However, no published data exist on the behavioral response of T. parvispinus to (Z)-3-hexenyl propanoate ((Z)-3-HP), a common HIPV known to influence herbivore behavior. The objective of this study was to evaluate the impact of (Z)-3-HP on T. parvispinus, filling a critical gap in current knowledge. Y-tube olfactometer assays were used to measure thrips choice between a leaf with clean air versus a leaf with the volatile present. Twenty individuals were tested at each dose and a control. Thrips were given three minutes to cross the decision threshold; individuals failing to choose were recorded as no response. Results showed that none of the tested doses elicited a statistically significant preference toward either treatment or control. Likewise, there was no significant association between dose and choice. While some doses leaned numerically toward one direction, limited sample sizes and high non-response rates restricted the ability to detect significance. Future work will expand to whole-plant assays that better mimic natural environments and provide stronger insights into the potential role of (Z)-3-HP in integrated pest management.

GP4: Stemphylium leaf blight severity and onion yield in relation to nitrogen-fixing bacteria and nitrogen fertilization

D. Blass, M.R. McDonald

Department of Plant Agriculture, University of Guelph, Guelph, ON

Stemphylium leaf blight (SLB), caused by Stemphylium vesicarium, is a major disease of onion in Ontario.  There has been recent discussion that provincially recommended nitrogen fertilizer rates for onions are too high, but increasing nitrogen rates have been associated with reduced susceptibility to SLB. Commercially available nitrogen-fixing bacterial endophytes could permit nitrogen fertilizer reductions while maintaining crop nitrogen status and limiting SLB; however, their effectiveness in onion production is not known. A field trial was conducted on a muck soil site (~ 70% organic matter) in the Holland Marsh, with direct-seeded onions grown at 0%, 50%, or 100% of the recommended nitrogen rate, or at 50% N, with the addition of either Gluconacetobacter diazotrophicus (Envita) or Methylobacterium symbioticum (Utrisha-N) applied as a foliar spray. Both endophyte treatments showed a trend of reduced SLB severity relative to other treatments, particularly later in the growing season, although these differences were not statistically significant. Foliar tissue analyses found no differences in nitrogen concentrations among treatments. All values were within or above sufficiency ranges, indicating nitrogen was adequate for optimal onion growth even at reduced nitrogen rates. Yield data are pending, but treatment effects are not expected. These results suggest provincially recommended nitrogen fertilizer rates for onions grown on muck soil may be lowered without compromising crop health or yield. The trends in reduced disease severity with endophyte treatments warrant further trials to clarify their potential role in integrated pest management regimes for controlling Stemphylium in onions produced under reduced nitrogen inputs.

GP5: Strawberry growing conditions and beneficial insects: The impact of low nighttime temperatures and LED lighting on aphid predators

K. Barton (1,2), R. Hallett (1), R. Labbe (1,2)

(1) School of Environmental Science, University of Guelph, Guelph, ON

(2) Agriculture and Agri-Food Canada, Harrow, ON

Novel LED regimes, such as Continuous and Blue Light Night Interruption (BLNI), have been developed to boost yield and/or reduce energy costs in controlled-environment (CEA) strawberry crops, and low night temperatures have been proven to improve fruit quality. While the impacts on the plants are well studied, little is known about the effects on beneficial insects. This study tested low nighttime temperature and novel LED regimes on development and predation rates of Aphidoletes aphidimyza, a key aphid predator. Experiments were conducted in controlled-environment cabinets with programmable LEDs. Predators were placed on strawberry leaf discs in petri dishes, where aphid consumption and development were recorded daily. Temperature had the strongest influence on predator performance. Without a nighttime temperature drop, larvae fed on more aphids per day and developed fastest. With a temperature drop, Continuous and Long-Day lighting produced similar development times and daily predation, while Short-Day and BLNI led to the slowest development and lowest daily predation. When examining total predation across the larval stage, nighttime temperature was less influential. The highest overall predation occurred under Short Day+Night Drop, Continuous–Night Drop, Continuous+Night Drop, and Long Day+Night Drop. The lowest occurred under Long Day–Night Drop and BLNI+Night Drop. These results suggest that treatments with lower daily predation were offset by longer larval development, leading to comparable or higher lifetime predation. This work highlights the importance of considering predator performance as well as crop performance when selecting CEA lighting and temperature strategies.

GP6: Canola verticillium stripe disease: Pathogenicity variations, co-existence with Leptosphaeria maculans, and transcriptome profile at adult plant stage

S. Reis (1), N. Archibald (1), S. Wilson (2), V. Bisht (2), Z. Zou (1)

(1) Department of Biology, Wilfrid Laurier University, Waterloo, ON

(2) Primary Agriculture, Manitoba Agriculture, Carman, MB

Canola (Brassica napus) is an essential and economically important crop to the Canadian economy. Canola is affected by many fungal diseases, including those caused by Verticillium longisporum and Leptosphaeria maculans, which allows for severe yield loss. Leptosphaeria maculans, the causal agent of blackleg disease, contains avirulence genes (Avr) that have a gene-for gene-interaction with resistance (Rlm) genes in canola. V. longisporum is the pathogenic agent of Verticillium stripe disease in canola. Together L. maculans and V. longisporum have a positive synergistic effect when a plant is co-infected. The relationship between V. longisporum and L. maculans is not well understood and will be addressed in this study. The variability of pathogenicity of V. longisporum populations in western Canada will also be tested. In this study, we will demonstrate that there is heterogeneity among V. longisporum genotypes and virulence across western Canada and identify L. maculans Avr gene profiles that can live synchronously with V. longisporum. This will be accomplished by using molecular identification and cotyledon inoculation tests. Dual-RNA sequencing analysis will be conducted to underline critical defense genes during the infection of canola by V. longisporum at adult plant stage. This study provides insight into the broadness of V. longisporum pathogen variation and its interaction with blackleg pathogen. The identified differentially expressed genes will serve as valuable genetic resources that can improve canola resistance against V. longisporum, which can be leveraged in future breeding programs.

GP7: Determining the preferred host plant for oviposition of three Canadian Dicyphus species and the adventive Nesidicoris tenuis (Hemiptera: Miridae)

C. Demers (1, 2), R. Hallett (1), R. Labbé (2)

(1) School of Environmental Sciences, University of Guelph,  Guelph, ON

(2) Agriculture and Agri-Food Canada, Harrow Research and Development Centre, Harrow, ON

Canada’s extensive greenhouse industry faces consistent and evolving pressure from established and invasive arthropod pests. Increasingly, pests strains exhibit resistance to chemical control methods, which makes the development of new biological control agents (BCAs) integral for continued management. Many mirid species are commercially available for use as BCAs around the world, but some omnivorous species have been known to damage crops in addition to reducing pest populations. Banker plants can be introduced into greenhouse systems to supplement BCA application by providing additional resources (e.g. food, prey, habitat). Conversely, trap plants function to attract pests, drawing them away from crops and reducing feeding damage. Over 60% of omnivorous mirids are polyphagous, giving them diverse host plant prospects, though many species show high fidelity for preferred hosts. Determining the host preferences of beneficial and detrimental mirid species can elucidate potential banker and trap plants for support of BCAs and integrated management of pests, respectively. We assessed the oviposition preference of four bryocorine mirids—established Canadian BCA Dicyphus hesperus, potential native BCAs D. famelicus and D. discrepans, and invasive plant pest Nesidiocoris tenuis— using whole plant choice-based assays, to compare preference for oviposition on mullein, strawberry, tomato, and alyssum seasonally. Additionally, cucumber, sesame, and tomato were offered to D. hesperus and N. tenuis to assess sesame as a trap plant in the presence of commonly associated crops. Nymphal emergence was used as a metric for adult oviposition preference. Preliminary results are presented and discussed, while further assessments of seasonal variation are ongoing.