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Important agricultural pests in the Canadian Prairies, wireworms are the soil-living larvae of click beetles. Several notable species are found within the Prairies, with Hypnoidus bicolor being the most ubiquitous in most parts of the region. Despite their prevalence, H. bicolor is often disregarded as a significant pest species due to their comparatively small larval sizes. However, few studies have directly assessed the capacity of wireworms to cause damage to particular crop(s), and thus far no such studies have been undertaken for H. bicolor. We therefore carried out laboratory experiments under controlled environmental conditions, with soil and wireworms transplanted from the field, to determine the capability of H. bicolor to damage soybean. As expected, wireworm damage was strongly associated with larval densities, with more severe soybean injury occurring in the presence of greater numbers of H. bicolor. Further, feeding damage to soybean by H. bicolor was greater at lower temperatures (10 °C and 20 °C) than at higher temperatures (30 °C). In terms of soil texture, soybean grown in loam and silt soils were the most susceptible to wireworm damage and those grown in clay soil were the least affected. Although the larvae are not capable of damaging soybean to the same extent as other Prairie pest species, Limonius californicus and Hypnoidus abbreviatus, in high enough densities and under ideal environmental conditions H. bicolor can significantly impact soybean growth. Overall, our study suggests that soybean is susceptible to considerable wireworm damage and H. bicolor is an under recognized pest species of this legume. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Wireworms have become a significant menace to cereals in the Northern Great Plains. Therefore, research toward developing effective control methods such as biological control with entomopathogenic nematodes (EPNs) is warranted. Two strains, each of two EPN species, Steinernema carpocapsae (Weiser) and Steinernema riobrave Cabanillas, Poinar, and Raulston in the form of infected Galleria mellonella (L.) cadavers were evaluated against wireworms in field and greenhouse. In field experiments, none of the four EPN strains were found effective against wireworms. However, in the greenhouse test, three of the strains, S. carpocapsae (All and Cxrd) or S. riobrave (355) applied in cadavers killed 50–68% of the sugarbeet wireworm, Limonius californicus (Mannerheim) was associated with 8–24% plant damage at 35 d after treatment (DAT), when seeds were treated with imidacloprid. The mortality range was 40–56% with 57–75% plant damage observed at 35 DAT, when seeds were planted without imidacloprid treatment. Synergistic effect among imidacloprid and S. carpocapsae (Cxrd) or S. riobrave (355) was observed in regard to L. californicus mortality. Additionally, effects of soil texture, moisture, and temperature on the infection rate of EPNs against L. californicus were examined in the laboratory. Limonius californicus mortality was not significantly affected by either soil moisture or soil types maintained at field capacity moisture levels. However, soil temperature showed a significant effect on L. californicus mortality. Overall, imidacloprid enhanced the infection and killing ability of EPNs against L. californicus and S. carpocapsae (All and Cxrd) strains were the virulent strains in different soil experiments. [ABSTRACT FROM AUTHOR]

Wireworms are destructive soil inhabiting polyphagous pests in the Pacific Northwest and Intermountain region of the United States. Continuously increasing wireworm populations and damage in small grain crops such as spring wheat in Northern Great Plains has become a challenge for growers. Due to unavailability of effective control measures, alternative methods, including biological control agents such as entomopathogenic nematodes (EPNs) are needed. Native/indigenous EPN species are expected to have better potential than exotic species to control the local insect pests. Two Montana native EPN species (Steinernema feltiae and Heterorhabditis bacteriophora) were tested against, Limonius californicus (Coleoptera: Elateridae) in laboratory and shade house studies. In the laboratory bioassay, two isolates of S. feltiae at the rate of 28,000 IJs/five larvae killed 48–50% of the insects within 4 wk. Heterorhabditis bacteriophora was not able to cause >30% L. californicus larval mortality. None of the two isolates of S. feltiae performed well against L. californicus when tested in different soil types. Similarly, two isolates of S. feltiae that were tested killed only 20–25% wireworms in a shade house trial that did not differ significantly from the control treatment. Four weeks after EPN treatment in the shade house trial, the percentage of wheat plant damage from L. californicus ranged from 30 to 40% in the presence of S. felitae , not differing statistically from control. These results suggest that S. felitae have limited potential in managing wireworm populations. [ABSTRACT FROM AUTHOR]

The polyphagous larvae of click beetles (Coleoptera: Elateridae) are major pests of spring wheat in Montana, USA. Presently available insecticides are unable to provide control over wireworm populations, and the use of natural enemies has not been successful under field conditions. In this study, we examined the effect of seven trap crops: pea, lentil, canola, corn, durum, barley, and wheat, for their attractiveness to wireworms compared to spring wheat. Experimental plots were located in two commercial grain fields in Valier and Ledger, Montana, USA and the trials took place from May to August in 2015 and 2016. Wheat plants damaged by wireworms were recorded and their relative locations in wheat rows and adjacent trap crop rows within a plot were determined using destructive soil samples. In 2016, variable row spacing (0.25, 0.5, 0.75, and 1 m) between the trap crops (pea and lentil) and wheat was assessed. Shade house bioassays were conducted using potted pea, lentil, and wheat plants to support field trial results. Limonius californicus larvae, released at the center of each pot were sampled 4 and 10 days after sowing. Wheat intercropped with pea and lentil had significantly fewer damaged wheat plants. Wireworm numbers were lower in wheat intercropped with pea compared to the control for both locations and years. Shade house results corresponded with field results, with more wireworms collected from pea and lentil than wheat. In the spacing trials, wheat plant counts were also significantly higher when paired with pea and lentil, particularly at 0.5 m spacing. Regardless of inter-row spacing, significantly fewer wireworms were associated with wheat when intercropped with pea and lentil trap crops. [ABSTRACT FROM AUTHOR]

The basic principles of a reliable integrated pest management program include pest identification, monitoring, and distribution. Selecting the appropriate sampling protocol to monitor wireworm for research or applied entomology depends on the objective, including simply detecting the presence or absence of wireworm, surveying the composition of wireworm assemblages, or estimating spatial and temporal population densities. In this study, the efficacy of pitfall, stocking, pot, and canister traps baited with wheat and barley mixtures was evaluated for monitoring wireworm populations in four commercial cereal fields in Montana. Pitfall and stocking traps collected greater numbers of wireworm (1625 and 1575, respectively) followed by pot-type and canister-type traps (1173 and 725, respectively). The 5098 wireworm collected from four sites included seven species: Aeolus mellillus, Agriotes sp, Dalopius sp, Hypnoidus bicolor, Limonius californicus, Limonius infuscatus, and S. aeripennis. [ABSTRACT FROM AUTHOR]

Wireworms are an increasing threat to the sustainable production of cereal, potato and other crops in Montana since the delisting of lindane, an effective and inexpensive insecti-cidal seed treatment. With this study, we have initiated long term research to investigate the di-versity of wireworm species infesting Montana's cropland. Canister-type bait traps were mailed to collaborating producers who buried them in established cereal fields for 10-14 days, and then returned them to Montana State University where the wireworms were identified to species. A total of 61 cereal fields in 12 counties were surveyed during 2011; 67 fields in 24 counties during 2012; and 66 fields in 16 counties during 2013. Wireworms were caught in 36.8% (46/125) of ce-real fields with no prior known history of wireworms, averaging 0.5 larvae per trap. Wireworms were caught in 62.7% (37/59) of fields with a reported history of wireworms, averaging 4.1 larvae per trap. The prairie grain wireworm, Selatosomus aeripennis (Kirby, 1837), was thought to be the most common species in the region. However, Limonius californicus (Mannerheim, 1843), L. infuscatus Motschulsky, 1859, Hypnoidus bicolor (Eschscholtz, 1829) and Aeolus mellillus (Saylor, 1836) were identified as the most common species in this study. Additionally, 2-3 different species often infested the same field. [ABSTRACT FROM AUTHOR]

• Wireworms, Limonius californicus are significant pests of wheat in Montana. • No effective control measures are available for wireworms. • Seed treatment with neonicotinoids can only repel the wireworms temporarily. • Entomopathogenic nematodes might help control wireworms. • Steinernema carpocapsae and Steinernema riobrave worked against wireworms in laboratory and indoor conditions. Wireworms, the larval stage of click beetles (Coleoptera: Elateridae), are economically important soil-dwelling pests that attack many field crops worldwide. Wireworms have become a serious threat to spring wheat in the Northern Great Plains because of lack of effective control measures, creating a need for alternative control methods such as biological control with entomopathogenic nematodes (EPNs). A laboratory bioassay was used to test ten EPN strains and identify infective EPN strains against the sugarbeet wireworm, Limonius californicus (Mannerheim) (Coleoptera: Elateridae). Steinernema carpocapsae (Weiser) (All and Cxrd strains) and S. riobrave Cabanillas, Poinar, and Raulston (355 and 7–12 strains) killed 60–70% of L. californicus larvae in four weeks when applied at 700 Infective juveniles (IJs) (25 IJs/cm2), 1400 IJs (50 IJs/cm2), 2800 IJs (100 IJs/cm2), and 5600 IJs (200 IJs/cm2) per larva in the laboratory. Also , Heterorhabditis bacteriophor a (Poinar) VS strain and Steinernema rarum (Doucet) 17c + e strain caused 50–60% mortality to L. californicus larvae after four weeks when applied at 5600 IJs/larva. However, regardless of the concentration applied, the penetration rate of infective juveniles into the host did not exceed 33%. In shade house trials, S. riobrave and S. carpocapsae strains caused 34–56% L. californicus mortality after four weeks with 50 and 56% mortality caused by S. carpocapsae All and S. riobrave 355 strain, respectively when applied at the rate of 80,000 IJs/pot. These results suggest that S. carpocapsae and S. riobrave may have significant potential for protecting spring wheat crops from L. californicus. [ABSTRACT FROM AUTHOR]