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: The Evenden Lab

*Text for this post prepared by Priyatha Sundaran, Sharavari Kulkarni and Maya Evenden, from the University of Alberta.

Dr. Maya Evenden’s lab in the Department of Biological Sciences at the University of Alberta researches insect behaviour, chemical ecology and integrated pest management. They study how insects orient and maneuver in their environment and exploit that knowledge for the development of IPM tactics. This summer the Evenden lab has multiple agriculture-based projects targeting diamondback moth, flea beetles, pea leaf weevil and alfalfa weevil. Here we highlight the work of an MSc student, Priyatha Sundaran, and a postdoctoral fellow, Dr. Sharavari Kulkarni.

Priyatha’s research focuses on the presence and distribution of alfalfa weevil (Hypera postica), in alfalfa grown for seed in southern Alberta. The study also assesses the diversity of Sitona spp. in sampled alfalfa fields. In three field seasons, alfalfa weevils have been sampled with soil and sweep samples, and emergence and pit fall traps. Soil samples at the beginning and end of each crop season estimate the density of alfalfa weevils in the soil over the winter. Sweep net samples can collect both larvae and adults to monitor alfalfa weevil density in the field for timely use of insecticides. Pitfall trap capture can indicate weevil movement in and out of the field over the course of the growing season. Emergence cages assessed the overwintering locations of weevils inside and outside the field. Initial results reinforce the effectiveness of sweep net sampling to monitor alfalfa weevil populations with peak larval activity in June-July. Alfalfa weevils were captured in equal numbers in pitfall traps placed at the edge and in the interior of the field suggesting that alfalfa weevils remain within alfalfa fields, unlike in other parts of their range. Sitona spp. bycatch consisted mostly of alfalfa curculio (Sitona lineellus) and pea leaf weevil (Sitona lineatus).

Alfalfa weevil sampling methods used in alfalfa fields grown for seed: A) Emergence cages were located inside and outside the field to reveal the overwintering sites of alfalfa weevils. B) Two hundred sweep samples were collected from four locations in each field throughout the growing season in three seasons. C) Directional pitfall traps were employed in the 2023 season to measure the direction of movement of alfalfa weevils in the field. Pictures by Priyatha Sundaran, University of Alberta.

Sharavari’s research focuses on developing weather-based stage-structured predictive models for two important canola pests, striped flea beetles, (Phyllotreta striolata (Fab.)) and crucifer flea beetles (Phyllotreta cruciferae (Goeze)). Flea beetles are oligophagous species feeding mainly on canola (Brassica napus L. and Brassica rapa L.) and mustard (Brassica juncea L.). Sharavari used field surveys to assess local phenology and laboratory bioassays to study the effect of temperature on beetle development and interspecific competition between the two species. The flea beetle surveys were conducted in the spring (pre-seeding) and fall of 2021, 2022 and 2023 across 20+ canola fields throughout Alberta.  Season-long, site-specific weather data was collected for modeling and validation. None of the available monitoring methods provides accurate forecasting for flea beetles, and weather-based phenology models can help producers make informed decisions on timing and the need to apply foliar insecticides for flea beetle management.  Lab assays showed a dramatic effect of temperature on the time and success of egg hatch and development time from egg to adult.  On-going lab work is testing for plant-mediated interactions between the two species to understand if P. cruciferae prefers to feed and oviposit on plants previously damaged by P. striolata and to determine if inter-species interactions have fitness costs.

Flea beetle monitoring in commercial canola fields with yellow sticky cards at sites with weather stations for site-specific temperature measurements. Pictures by Sharavari Kulkarni, University of Alberta.

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.

Prairie Research

Science News from the Prairies

A new issue of the newsletter, Science News from the Prairies is now available! This issue highlights the Agriculture and Agri-Food Canada information booth that can be found at Ag in Motion (July 18-20, 2023), new publications arising from prairie research, and upcoming events.

Developing Economic Thresholds for Lesser Clover Leaf Weevil

*This text was prepared by Jeremy Irvine and Sean Prager from the University of Saskatchewan.

Red clover (Trifolium pratense) is a short-lived perennial crop grown for seed production. Red clover seed is an important commodity in the Canadian Prairies, providing upwards of $2 million annually to the Saskatchewan economy. The production of red clover seed can be affected by the lesser clover leaf weevil (Hypera nigrirostris; LCLW). Yield losses of up to 50% have been recorded with high infestations of the LCLW. The weevil larvae feed on the developing shoots, flower heads, and seeds of red clover plants. Larvae cause the worst damage but secondary feeding damage can occur once LCLW larvae become adults.

Lesser clover leaf weevil damage, resulting when larvae exit the stem of the host plant. Picture credit: Jeremy Irvine, University of Saskatchewan.

Lesser clover leaf weevils are traditionally controlled using insecticides, but these can have negative impacts on  non-target insect species, notably bees. Managed bee species are used by red clover seed growers to ensure fields receive adequate pollination, high seed set, and subsequent yield.

There are currently no established economic thresholds for control of LCLW and insecticides can be applied when they are not needed, which increases the cost of clover production, negatively affects pollinators, and could contribute to the development of insecticide resistance in the LCLW population. The threat of insecticide resistance is significant because there is only one registered active ingredient for LCLW.  

A field trial near Carrot River, Saskatchewan is set up in second-year red clover to study the lesser clover leaf weevil. Picture by Jeremy Irvine, University of Saskatchewan.

The primary purpose of this research, which began in May 2023, is to develop an economic thresholds for LCLW in red clover crops. The project will also study the development of LCLW in varying weather conditions so that seasonal development can be incorporated into the economic thresholds. Finally, the project will generate a sequential sampling plan, meant to assist with the decision-making process to optimize management of LCLW. To conduct this research, we will work with farmers to conduct on-farm field trials where LCLW population densities will be manipulated and red clover yield will be quantified to determine the relationship between weevil density, injury level, and yield loss.

The overall goal of our project is to develop new tools that can be used to manage LCLW and protect red clover seed yields. Financial support for this study was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Government of Saskatchewan Agriculture Development Fund (ADF) and the Saskatchewan Forage Seed Development Commission (SFSDC).

Prairie Research

Developing tools for the management of Lygus bugs in faba bean

*The text of this post was written by Teresa Aguiar-Cordero and Sean Prager.

This research project, led by Sean Prager and Teresa Aguiar-Cordero, focuses on studying insects in the genus Lygus and their impact on faba bean crops in the province of Saskatchewan. Faba beans are a significant legume crop in the region, but they face threats from various insect pests, including Lygus species. Lygus bugs feed on faba beans by injecting salivary enzymes into the plant, resulting in damage such as hull perforations, seed coat discoloration, and tissue wilting which reduces yield. Damage to seed lowers the quality and grade of faba beans below that for human consumption with substantial economic consequences.

Microscope image of an adult Lygus bug. Picture provided by Teresa Aguiar-Cordero, University of Saskatchewan.

The project aims to address crucial knowledge gaps regarding Lygus bugs in faba beans. By conducting a survey across Saskatchewan, the study aims to determine the optimal timing and methods for effective Lygus sampling. In addition to the survey, a series of no-choice bioassay are currently being performed to quantify the relationship between Lygus bug numbers and the resulting damage to faba bean pods, which can help develop action thresholds.

Faba bean pods with damage resulting from Lygus bug feeding activity. Picture provided by Teresa Aguiar-Cordero, University of Saskatchewan.

As part of the future directions, the researchers plan to incorporate the electrical penetration graph technique (EPG) to gain a better understanding of the feeding behavior of Lygus bugs in faba beans. This technique will provide valuable insights into the precise feeding patterns employed by Lygus bugs.

In addition, a series of choice bioassays will be conducted to analyze and determine the preferences of Lygus when given a choice of different crop and plant species. This will help establish which crops Lygus may migrate into faba bean from. By studying the preferences of Lygus bugs for different crops, the researchers aim to identify potential trap crops that can attract Lygus populations as part of a management program to reduce the impact of Lygus bugs on faba bean crops.

The project’s outcomes will contribute important information and management tools for growers, enabling them to mitigate the impact of Lygus insects on faba bean crops. By understanding the associations between Lygus numbers and damage, and exploring innovative strategies such as trap crops, the project strives to minimize damage and decrease losses for growers.

Teresa Aguiar-Cordero is a graduate student at the University of Saskatchewan, working with Dr. Sean Prager to study Lygus bugs.