Seasonal turnover and insights into the overwintering biology of wireworms (Coleoptera: Elateridae) in the Canadian Prairies.

BACKGROUND: The long-lived terricolous larvae of click beetles, colloquially called wireworms, pose a significant threat to agriculture worldwide. Several economically important pest species have been documented in the Canadian Prairies, including Hypnoidus bicolor, Limonius californicus and Hypnoidus abbreviatus. However, most monitoring activities are performed in the early spring and there is evidence from other geographical regions of seasonal shifts in wireworm species composition and prevalence. Further, little is known about the overwintering physiology or behaviors of wireworms, which undoubtedly contribute to their population dynamics. RESULTS: We surveyed wireworm populations from four Manitoban fields six times throughout the 2020 and 2021 growing seasons. Both Hypnoidus species were active throughout the spring and summer; however, L. californicus did not become active until later in the spring. Chill-coma recovery assays indicated Hypnoidus species recovered quicker than L. californicus from cold acclimation. Vertical migration assays simulating progressively lower ambient temperatures experienced by overwintering larvae identified H. bicolor throughout the soil profile, with L. californicus preferentially found at cooler, shallower depths. We speculate that these differences in species distribution within the soil column are due to the higher levels of putative cryoprotectants (for example, trehalose, sorbitol, glucose, glycerol) in L. californicus, as identified by targeted liquid chromatography tandem mass spectrometry. CONCLUSION: Our findings of a stark seasonal turnover in wireworm species prevalence and composition in the Canadian Prairies should be incorporated into future integrated pest management and surveillance activities. This study also advances our understanding of wireworm overwintering biology, which should be factored into current management approaches. © 2022 His Majesty the King in Right of Canada. Pest Management Science © 2022 Society of Chemical Industry. Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada.

Evaluation of Standardized Bait Trapping Approaches and Climatic Factors That Influence Wireworm Catch in the Canadian Prairies.

Wireworms are significant pests of a variety of economically important crops grown in the Canadian Prairies. These soil-dwelling larvae of click beetles feed on and burrow into the accessible underground plant tissues, which can result in cosmetic injury, stunting, wilting, and plant death. Successful management of wireworms relies on accurate estimations of their abundance and activity in infested fields. Bait trapping is the most commonly used method for sampling wireworms and standardized approaches have been developed; however, little work has been done to optimize trapping efficacy in different geographical regions. In this study, we evaluated the effect of bait trapping duration, seed formulation, and the causal relationship with CO2 production and soil temperature on the wireworm catch in three fields located in Manitoba, Canada. As expected, wireworm catch increased with trapping duration and placing traps in ground for 8 d is adequate in most cases. Both barley and wheat were more effective baits than soybean; however, barley released more CO2 (i.e., an attractant for wireworms) and performed better at elevated soil temperatures. Overall, the results of this study will serve as valuable guidelines to improve current wireworm sampling methods, and can be integrated into strategies aimed at managing these important pests to crop production.

Three years of surveillance associates agro-environmental factors with wireworm infestations in Manitoba, Canada.

BACKGROUND: Wireworms, the soil-dwelling larvae of click beetles, are a major threat to global agricultural production. This is largely due to their generalist polyphagous feeding capabilities, extended and cryptic life cycles, and limited management options available. Although wireworms are well-documented as economically important pests in the Canadian Prairies, including Manitoba, there are gaps in knowledge on species distributions, subterranean behaviour and life cycles, feeding ecology and damage capacity, and economic thresholds for crop yield loss. RESULTS: We carried out 3 years (2018-2020) of intensive surveillance of larval populations across Manitoba. A total of 31 fields (24 in ≥ 2 consecutive years) were surveyed in early spring using standardized bait trapping approaches. Wireworms were present in 94% of surveyed sites, but the catch within fields varied year to year. While Hypnoidus bicolor predominated (94% of larvae), several other pest species were identified. We then explored the relationships between wireworm trap numbers and agro-environmental factors. The larval catch tended to decrease under conditions of low soil temperatures and increased clay content, coupled with high soil moisture and precipitation during the trapping period. Treatment and cultural methods appeared less influential; however, wheat production in either of the previous two growing seasons was associated with increased wireworm catch. Our models failed to predict a relationship between wireworm catch and crop yields, although infestations were rare in our region. CONCLUSION: Our findings better infer the risks posed by wireworms to crop production in the Canadian Prairies, and the agro-environmental factors that represent the greatest contributors to these risks. This information should be incorporated into future integrated pest management (IPM) strategies for wireworms. © 2021 Her Majesty the Queen in Right of Canada Pest Management Science © 2021 Society of Chemical Industry Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada.

Occurrence of the Mosquito Aedes triseriatus (Diptera: Culicidae) Beyond Its Most Northwestern Range Limits in Manitoba, Canada.

Native to the Eastern United States and Eastern Canada, Aedes triseriatus (eastern tree hole mosquito) is an important vector of La Crosse virus and dog heartworm. Although its range has been well characterized in the United States, few studies have surveyed its distribution within Canada. In this study, mosquitoes were collected from a variety of urban and rural communities throughout Manitoba, Canada between the years of 2018 and 2020. Aedes triseriatus was identified and confirmed molecularly to be present in 13 communities. This includes localities that expand the species known distribution to new northern and western areas, and suggests that past surveillance efforts have not been comprehensive or environmental factors have caused this mosquito species to be present in areas in which it was not found previously. As Canada is showing signs of a changing climate, this may be driving the broader occurrence of Ae. triseriatus.

Genetic structure and population demographics of Hypnoidus bicolor (Coleoptera: Elateridae) in the Canadian Prairies.

BACKGROUND: Following banning of the pesticide lindane in most counties, wireworms (i.e., the soil-living larval stages of click beetles) have become major pests of a variety of economically important field crops. Hypnoidus bicolor is a common pest species in the Canadian Prairies. However, little is known about its life history, which impedes the development of effective integrated pest management (IPM) strategies. Population genetic approaches have the potential to assist in the development of IPM. RESULTS: We sequenced a 622-bp fragment of the COX1 gene from 326 H. bicolor wireworm and click beetles collected from 13 localities on the Canadian Prairies. Two genetically distinct (>4.66% sequence divergence) clades were identified, suggesting that they may be part of a species complex. Clade A predominated and increased in prevalence the further east samples were collected, whereas the opposite was true for clade B. Clade B appears to be comprised of two mitochondrial DNA groups, however, one group was represented by only one haplotype. Both clades were characterized by uneven gene flow among populations with low levels of regional genetic structuring. Clade A appeared to have undergone population and range expansions, which may coincide with the advent of intensive agriculture practices in the prairies. CONCLUSION: Knowledge of species composition and population structure is important for the development of effective IPM strategies but is often lacking for wireworms. Our study fills these knowledge gaps for a predominant pest species in the prairies, H. bicolor, by providing robust evidence for cryptic forms and characterizing its dispersal patterns and population dynamics. © 2021 Society of Chemical Industry.