Prairie Research: Carabid Beetles that help Manage Weeds

*Text for this post prepared by Daniella Canon-Rubio and Christian Willenborg, University of Saskatchewan.

At the University of Saskatchewan, Christian Willenborg, Khaldoun Ali, and Daniella Canon-Rubio are studying the role of carabid beetles in the biological control of weeds. These remarkable beetles have gained acclaim for their vital ecological role across diverse agroecosystems, including as predators of pest insects and for contributing to weed management by actively reducing the population of weed seeds in agricultural fields.

Stereoscope image of an adult of Pterostichus melanarius. Picture provided by Daniella Canon-Rubio, University of Saskatchewan.

The seed selection process in carabid beetles is a multifaceted phenomenon, subject to the influence of various ecological factors. The objective of Daniella’s study is to examine the effects of imbibition on the preferential tendencies exhibited by Pterostichus melanarius and Amara littoralis carabid beetles towards the seeds of Bassia scoparia (kochia) and Thlaspi arvense (stinkweed).

Stereoscope image of Thlaspi arvense seed eaten by P. melanarius next to an intact seed. Picture provided by Daniella Canon-Rubio, University of Saskatchewan.

Their research will involve conducting field experiments to trap live adult insects using pitfall traps. In the laboratory at the University of Saskatchewan, studies in controlled feeding environments will be conducted with varying imbibition length times to allow for the evaluation of seed preferability and consumption. Seed imbibition occurs when dry seeds take up water. Concurrently, we will utilize an olfactometer to evaluate how the odor emitted by Bassia scoparia and Thlaspi arvense seeds, treated with various imbibition times, influences the seed selection and favorability of Pterostichus melanarius and Amara littoralis. To integrate and analyze the behavioral data obtained from this experiment, we will employ Ethovision, a sophisticated software platform, to track the subjects through video analysis, perform movement analysis, and accurately identify specific behaviors exhibited by the beetles.

Through the implementation of this research on biological control in conservation, our objective is to significantly expand and enrich the knowledge base concerning carabid beetles and their feeding behavior in relation to diverse weed seed characteristics. By fostering a comprehensive understanding, we seek to promote awareness among farmers and fellow researchers about the valuable role carabid beetles play as beneficial organisms in North America. Furthermore, we aim to encourage the utilization of carabid beetles as an alternative approach to weed management.

Prairie Research

*This text was prepared by Kanishka Seneveirathna, Natalie LaForest, and Boyd Mori from the University of Alberta

Under the supervision of Dr. Boyd Mori at the University of Alberta, the ecological and agricultural entomology lab employs diverse molecular methods to tackle pest-related problems and develop integrated pest management approaches. Here we highlight research conducted by two graduate students: Kanishka Seneveirathna and Natalie LaForest.

Kanishka’s research uses population genetics to detect and monitor invasive insects in the prairie ecosystem. His research focuses on reconstructing the invasion routes of wheat midge (Sitodiplosis mosellana) and diamondback moth (Plutella xylostella), two devastating pests, by determining their origins in North America. To understand their invasion patterns, Kanishka employs a genomic approach (RADSeq), which allows for genome-wide population structure analysis.

A pheromone trap (left) used to collect adult wheat midge for population genetic analyses. The adult midge are trapped on a sticky card (right). Pictures by Kanishka Seneveirathna, University of Alberta.

By reconstructing the invasion routes of these pests, Kanishka aims to identify their origins and determine the genetic diversity and structure of different populations. This comprehensive understanding will facilitate the development of integrated pest management strategies, including forecasting systems and insecticide resistance management strategies. Initial findings indicate multiple independent invasion events for wheat midge across North America.

Moving forward, Kanishka and the Mori Lab team will work with members of the PPMN to collect a larger number of samples across the Prairies, ensuring comprehensive coverage. Collaboration with international research groups is also on the agenda, enabling the validation of findings and broader knowledge exchange. The goal is to develop effective management strategies to mitigate the damage caused by these invasive pests and enhance the productivity and quality of canola and wheat crops in the Canadian Prairies.

Pheromone traps (A) are used to collect adult diamondback moths in canola fields. Once trapped, the moths are removed from the sticky cards that are placed on the floor of the pheromone trap (B). To collect diamondback moth larvae for population genetic analyses, canola is sampled using sweep nets (C). Pictures by Kanishka Seneveirathna, University of Alberta.

Natalie’s research focuses on integrated pest management, more specifically the ecosystem service of weed seed predation performed by ground beetles (Coleoptera: Carabidae). Previous research on determining the species of weeds consumed by this group of beneficial insects have used seed cards in the field or cafeteria choice tests in the laboratory. Natalie’s work uses a multiplex-PCR approach, where she uses the DNA found within the gut of field captured ground beetles to determine what the ground beetles are consuming in the field. She is designing species-specific primers of agronomic significant weeds to decipher this significant predator-prey interaction. 

Throughout the 2021 and 2022 seasons, the most abundant ground beetle species collected has been Pterostichus melanarius, which is an introduced, opportunist generalist predator. Natalie is focusing on ground beetles in wheat and industrial hemp, but there are other members in the Mori lab looking at the prey items of ground beetles in canola and pulses. Identifying species specific predator-prey interactions will development more sustainable pest management strategies for producers.

A pitfall trap full of adult ground beetles (Coleoptera: Carabidae); pitfall traps are used to collect ground beetles and other insects during the growing season. Picture by Natalie LaForest, University of Alberta.


Pea leaf weevils may be prowling legume crops, but ground beetles and rove beetles are on the hunt as well. This Insect of the Week features two large groups of insects: ground beetles (Carabid beetles) and rove beetles (Staphylinid beetles). Many of species of ground beetles and some rove beetles are generalist predators, like ants, centipedes and spiders. These arthropods are not picky when it comes to choosing a meal and they often target pests in crop fields. 

From left to right, a Carabid beetle (about 2 cm long), a Carrion beetle (about 2 cm long) and a Staphylinid beetle (less than 1 cm long). Photo credit: Jonathon Williams, AAFC-Saskatoon.

Based on research conducted in western Canada, at least two species of ground beetle have pea leaf weevil on the menu. First, a small beetle called Bembidion quadrimaculatum can feast on pea leaf weevil eggs.

Small bodied (2-3 mm long) Bembidion quadrimaculatum ground beetles can eat pea leaf weevil eggs. Photo credit: Shelby Dufton, AAFC-Beaverlodge Research Farm

A larger beetle called Pterostichus melanarius will catch and eat adult pea leaf weevils. Other pests that different ground beetle species may eat include cutworms, aphids, wheat midge, cabbage root maggots, slugs, and many others! 

A pinned Pterostichus melanarius specimen. These ground beetles eat larger prey, including adult pea leaf weevils. Photo credit: Shelby Dufton, AAFC-Beaverlodge Research Farm
A ground beetle (likely from the genus Pterostichus) next to a finger for scale. Photo credit: A. Harpe, AAFC-Beaverlodge Research Farm

Ground beetles are characterized by long threadlike antennae, have a body that is flattened top-to-bottom, and have strong legs designed for running, large eyes, and obvious jaws (mandibles).  

Rove beetles, like ground beetles, can be important predators of a number of insect pests! Some species will feed on pea leaf weevil eggs. One species of the rove beetle, Aleochara bilineata, is an important natural enemy of cabbage, seedcorn, onion and turnip maggots. Rove beetles are small, thin and have shortened fore-wings that leave most of their abdomen exposed.  

A pinned Staphylinid (rove) beetle (<1cm long). Photo credit: Shelby Dufton, AAFC-Beaverlodge Research Farm

For more information on these field heroes and the other pests they help to manage, see the Field Crop and Forage Pests and their Natural Enemies in Western Canada guide. The guide has helpful information about the life cycle of these and other predators. The guide also has tips for conserving predators and parasitoids and pictures to help with identification. Please visit the PPMN Field Guide page to download a copy of the guide in French.

Insect of the Week – Pterostichus melanarius

This week’s insect is the ground beetlePterostichus melanarius (Coleoptera: Carabidae).  This large (12-19 mm), shiny black beetle originates from Europe and probably arrived to North America in the 1920s in ships’ ballasts. It has become a widespread insect throughout North America, particularly in habitats used by humans: urban areas, forests, and agricultural land.

Flight has been the main method of colonization and dispersal for this species. In newly arrived populations of P. melanarius, individuals generally have longer hind wings which allow for more efficient dispersal. After a population has become established in an area, short-winged morphs of the species become dominant.

This species is an excellent example of a generalist predator. Generalist predators include many species of ground beetles, some rove beetles, ants, centipedes and spiders. These arthropods are not picky when it comes to choosing a meal. For example, P. melanarius will eat nearly anything including many different arthropods, earthworms, slugs and even some small vertebrates. Generalist predators are effective in keeping some insects from reaching high numbers that can damage agricultural crops.

Find out more about ground beetles and Pterostichus melanarius at the Insect of the Week page!

Pterostichus melanarius
Photo credit: Henri Goulet (retired), Agriculture and Agri-Food Canada
Photograph of Pterostichus melanarius catching a fourth-instar P. xylostella in a plastic container (LRC, Photo credit: A. Mauduit)

Insect of the Week – Ground beetles: cutworm natural enemies

This week’s Insect of the Week is a large group of insects called ground beetles, also known as carabid beetles. Many species feed on cutworms as well as other pests.

Almost 400 different species of ground beetles occur on the Prairies, ranging in size from just a few millimetres to more than 2 centimetres. A field may contain 50 or more species, with densities ranging up to 10 beetles per square meter.

Ground beetles are characterized with long threadlike antennae, have a body that is flattened top-to-bottom, and have strong legs designed for running, large eyes, and obvious jaws (mandibles). Smaller ground beetle species can be important predators of cutworm eggs. Larger species attack and kill fully-grown cutworm larvae.
With all the work they do protecting your crop, ground beetles are real @FieldHeroes.
Find out more about ground beetles at the Insect of the Week page!
Adult Carabus nemoralis attacking a bertha armyworm caterpillar. 
Photocredit – Vincent Hervet, Agriculture and Agri-Food Canada
Species of ground beetles common in agricultural fields on the Prairies. 
From left to right: Bembidion quadrimaculatum, Agonum cupreum, 
Pterostichus melanarius, Calosoma calidum
Photocredit – Henri Goulet (retired), Agriculture and Agri-Food Canada

For a detailed review of ground beetle research, biology, distribution, habitat, diet, etc., see Chapter 1: Ground Beetles (Coleoptera: Carabidae) of the Prairie Grasslands of Canada.
**NEW – Don’t forget there’s a new cutworm identification manual you can download from the Cutworm Field Guide page – NEW**


Insect of the Week – Ground beetles

Ground beetles (predator)

Last year, the focus of the Insect of the Week was crop pests. This year, we’re changing things up and highlighting the many natural enemies that help you out, silently and efficiently killing off crop pests. [note: featured Insects of the Week in 2015 are available on the Insect of the Week page] 

This week’s Insect of the Week is the ground beetle. There are nearly 400 known ground beetle species on the prairies. Some of these provide important pest control service: eating redbacked cutworm eggs, grasshopper eggs, pea leaf weevil eggs, cabbage maggots and diamondback moth larvae. See more information in the new Field Crop and Forage Pests and their Natural Enemies in Western Canada – Identification and Management Field Guide for identification, life cycle and conservation options (download links for field guide available on the Insect of the Week page).

The ground beetle Pterostichus melanarius can help prevent pest outbreaks of diamondback moth (Plutella xylostella). © Canadian Biodiversity Information Facility (
For those that just can’t get enough about the fascinating world of insects, Ground Beetles (Coleoptera: Carabidae) of the Prairie Grasslands of Canada is a recent literature review on the topic.