Tracking the movement of flea beetles across the Canadian Prairies

Term: 2 years, beginning 2024
Status: Ongoing
Researcher(s): Boyd Mori, U of A
SaskCanola Investment: $70,871
Total Project Cost: $212,614
Funding Partners: ACPC, MCGA

Objective

1. Survey flea beetle populations across Alberta, Saskatchewan, and Manitoba to determine species composition and movement of beetles between regions. 

2. Conduct a field-level study to determine if flea beetles associated with non-crop hosts contribute to populations in adjacent commercial canola crops. 

Project Description

Striped and crucifer flea beetles are chronic pests of canola grown on the Canadian Prairies and as a result over 99% of canola seed is treated with a neonicotinoid insecticide. The flea beetles are known to differ in their tolerance to the neonicotinoids with striped being more tolerant than crucifer flea beetles. Our current project (Ag Funding Consortium: 2021F062R) has found potential differences in the tolerance of both flea beetle species to the neonicotinoid seed treatments depending on collection region. In addition, the two species have differences in their overall physiology in terms of cold temperature tolerance (striped emerge early in the spring) and flight ability (crucifer flies more actively than striped). These differences may affect the overall distribution of flea beetles within and across regions on the Prairies and have implications for management. 

Flea beetles mainly overwinter in field margins and emerge in the spring to feed on weedy cruciferous species and volunteer canola, prior to colonization of commercial canola fields. Depending on the insect species, non-crop hosts impact the colonization of crops. For example, cereal aphids, feeding on non-crop hosts in the field margin contribute little to the populations in adjacent cereal crops, whereas, populations of the legume pod borer, on both crop and non-crop hosts were intermixed, indicating movement of individuals between adjacent hosts in the same vicinity. The movement of flea beetles between non-crop hosts and commercial canola is unknown and may have implications for resistance management. Flea beetles reproducing on non-crop hosts escape the selection pressure to develop insecticide tolerance/resistance (seed treatments or foliar), and if they mate with those under such pressure in canola it reduces the likelihood of further tolerance developing. However, if beetles on canola are generally associated with canola and do not mix with those on non-crops, there is higher selection pressure on these individuals leading to increased tolerance/resistance to insecticides. 

Given their small size, the movement of individual flea beetles is difficult to monitor, however population genetic approaches can elucidate dispersal and movement of insects via measurements of population structure and gene flow. Additionally, population genomic approaches can provide additional understanding of the genetic basis of insect pest physiology, behavior, ecology, and dispersal. In agroecosystems, pest populations can be subjected to strong selective pressure from crop rotation (e.g., corn rootworm host shift to soybean), resistant varieties, insecticide application and transgenic crops, and climate conditions. Given their small size, differences in various physiological, behavioral, and levels of tolerance to insecticides, and potential differences in movement between non-crop and crop hosts, knowledge of population structure and the movements of these pests would be beneficial for management, including modelling and forecasting. 

Leveraging collaborators and samples collected as part of the Prairie Pest Monitoring Network, this study will survey beetles across the Prairie provinces and examine the genome-wide population structure to track the movement and dispersal ability within and between regions and host plants. This will be the first genomic quantification of dispersal of these species in Canada and may guide research and management of other flea beetle species. Additionally, based on results of ongoing research (AFC: 2021F062R), we can use this population genomic data to identify genomic regions associated with insecticide tolerance/resistance, which is vital to understanding the mechanisms of this tolerance. This research will allow us to determine if vast acres of canola have increased selection pressure on insecticide tolerance levels of flea beetles and if non-crop hosts play a role in insecticide resistance management. It will also provide knowledge to determine if the putative regional differences in tolerance levels to seed treatments can spread to other areas. Finally, results of this research will directly inform modeling and forecasting of flea beetle movement through the prairies at both broad and fine geographic scales.