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The application of fungal entomopathogens, such as Metarhizium brunneum, has the potential to continue to impact targeted host populations through secondary cycling. In the present study, we examined the horizontal transmission of M. brunneum conidia from conspecific mycosed cadavers or soil on which the cadavers sporulated to Agriotes obscurus beetles. Close contact between the susceptible hosts and sporulating cadavers or contaminated soil was required for increased mortality of hosts and subsequent production of mycosed cadavers. [ABSTRACT FROM AUTHOR]

A study was conducted to determine rates of recapture of marked Agriotes obscurus (AO) males released in a grassy field on four occasions in the centre of pheromone trap squares with traps spaced 2.5, 5.0, 7.5 and 10.0 m apart. Concurrent catches of naturally occurring and naturally dispersed (wild) AO were also recorded. Catch of marked AO was highest during peak emergence when maximum weekly temperatures ranged from 15.7 to 17 °C, and rainfall was light. Mean catch in the 2.5–10.0 m trap squares was, respectively, 82.0, 79.0, 77.0 and 65.0%, which occurred within one week of release. Catch of marked AO were lower (range in 2.5–10.0 m squares: 74.5–50.5%) when released early in the activity period, due to lower temperatures and higher rainfall, and catch was protracted over 3 weeks. Catch during two releases under favourable weather late in the activity period was also reduced (range: 25–58%), likely due to loss of AO vigour and/or pheromone trap efficacy. Catch of wild AO was highest in traps spaced 7.5 or 10.0 m apart, suggesting independence of these traps, and between-trap competition at 2.5 and 5.0 m spacings. From these data, we estimated that an effective spacing for traps in mass trapping arrays would be approximately 6 m. Significantly higher catch of marked or wild AO occurred in traps that were upwind in all trap squares, indicating wind direction should be considered in structuring the placement of trap arrays in mass trapping programs in non-farmed headland areas. [ABSTRACT FROM AUTHOR]

We evaluated the relative efficacy of six pheromone-baited traps used in trapping Agriotes obscurus (L.) click beetles (Coleoptera: Elateridae): original Yatlor Traps, Yatlor Funnel Traps, Vernon Beetle Traps, Unitraps, Baited Pitfall Traps, and Vernon Pitfall Traps. Traps were rated according to quantitative and qualitative criteria of importance for each of four trap uses: general surveys, scientific studies, IPM monitoring, and mass trapping. Measurable quantitative categories included: total catch of A. obscurus; time for assembly, installation, and inspection; exclusion of nontarget invertebrates; and cost. Qualitative criteria were small mammal exclusion, flooding, design and handling variability, and convenience for various field uses. The most desirable characteristics were determined for the above four uses, and the cumulative ranking based on quantitative criteria and all four uses was Vernon Pitfall Trap, Baited Pitfall Trap, Original Yatlor Trap, Vernon Beetle Trap, Yatlor Funnel Trap, and Unitrap. [ABSTRACT FROM AUTHOR]

Trade‐offs in the time and energy allocated to different functions, such as reproductive activities, can be driven by alterations in condition which reduce resources, often in response to extrinsic factors such as pathogens or parasites. When individuals are challenged by a pathogen, they may either reduce reproduction as a cost of increasing defence mechanisms or, alternatively, modify reproductive activities so as to increase fecundity thereby minimizing the fitness costs of earlier death, a behaviour consistent with the terminal investment hypothesis (TIH). The TIH predicts that individuals with decreased likelihood of future reproduction will maximize current reproductive effort, which may include shifts in reproductive timing. We examined how wild, adult female click beetles (Agriotes obscurus) responded after exposure to the fungal pathogen Metarhizium brunneum. Field‐collected beetles exposed to a high concentration of M. brunneum died earlier and in greater numbers than those exposed to a low concentration. Using a multivariate approach, we examined the impact of pathogen challenge on lifespan and a suite of reproductive traits. Stepdown regression analysis showed that only female lifespan differed among the fungal treatments. Fungal‐induced reductions in lifespan drove changes in the reproductive schedule, characterized by a decrease in preoviposition period. Moving the start of egg laying forward allowed the females to offset the costs of a shortened lifespan. These changes suggest that there is a threshold for terminal investment, which is dependent on strength of the survival threat. From an applied perspective, our findings imply that exposing adult click beetles to M. brunneum to reduce their population density might not succeed and is an approach that needs further investigation. [ABSTRACT FROM AUTHOR]

Mark-release-recapture was used to investigate the dispersal of click beetles in spring wheat or fallow fields using edge or centre field releases. Three types of pitfalls were used: gutter traps near field margins, as well as conventional pitfall traps or cross-traps consisting of four gutter trap arms leading to a central pitfall. Capture of naturally occuring beetles was concurrently recorded., In total, 6952 marked Agriotes obscurus (males and females) and Agriotes lineatus (males) were released and 14.74% were recaptured at some time during the present study. Recovery rates ranged from 3.54% to 28.5%., Agriotes obscurus dominated wild populations, with 4011 males and 1672 females trapped compared with 17 males and three females for A. lineatus. Males dominated early in the period, although the sex ratio tended towards equality as the season progressed., Generally, captures of A. obscurus males released in equal numbers at field edges followed a uniform distribution. There were differences for wild beetles caught in the same traps., Spatial trapping patterns of wild and marked beetles across the fields were similar. Within 19 h of release at the field edges A. obscurus males were captured >30 m away., The crop type had a significant interspecific effect on trap counts for males and an intraspecific effect on A. obscurus females, reinforcing the need for caution when using trapping systems to monitor adult stages of these pests., The results of the present study demonstrate that uncropped field margins comprise sources of click beetles. We also conclude that click beetles disperse much further than reported previously. [ABSTRACT FROM AUTHOR]

A combined application of a biological control agent, such as an entomopathogenic fungus ( EPF), with other means of pest control may lead to enhanced or more reliable efficacy of the biocontrol agent. Ideally, the combined components would interact synergistically, yielding significantly higher mortality of the target pest. The mode of such interactions is often unclear and particularly difficult to elucidate for soil-dwelling pests. Here, an efficient image analysis protocol was developed to study behavioural responses of soil-dwelling insects to application of control measures in two-dimensional terraria. The interactions between the EPF Metarhizium brunneum Petch ( Hypocreales), a supposedly repellent extract of garlic, Allium sativum L. ( Amaryllidaceae), and wireworms, Agriotes obscurus (L.) ( Coleoptera: Elateridae), as target hosts were investigated. Tunnelling activity and mortality of wireworms were studied under choice and no-choice situations of various combinations of the control agents. A treatment with Metarhizium spores resulted in wireworm mortalities of about 80%. Contrary to expectations, a combination of the EPF with the garlic extract did not increase, but slightly decrease wireworm mortality. The data gained from the image analysis revealed that the tunnelling activity of wireworms was clearly reduced in the presence of garlic, which, together with a reduced germination rate of spores, is a possible explanation for the antagonism detected in the combined treatment. The methodological approach developed here can be used to study the interactions among control agents and soil insects over several days and weeks. [ABSTRACT FROM AUTHOR]

Insecticide-treated seed is commonly used to manage wireworms, with insecticide toxicity generally being deduced from crop stand protection rather than from directly observed wireworm responses. We observed the behaviour of larvae of two economic elaterids exposed to wheat seeds treated with 11 insecticides at various rates or combinations in a soil environment. Wireworms were exposed for 3 or 24 h, and the post-contact health and mobility of 1030 larvae that contacted seeds were assessed (bi)weekly for 12-42 weeks. Considerable repellency was observed when wireworms were exposed to bifenthrin, tefluthrin, λ-cyhalothrin, and some repellency was also observed at high rates of various other insecticides. A high proportion of wireworms were moribund after 24 h when exposed to treatments containing thiamethoxam, fipronil, or high rates of ethiprole, cyazypyr, chlorpyrifos, and spinosad, but not after exposure to bifenthrin, tefluthrin, chlorantraniliprole, spirotetramat, or low rates of ethiprole, cyazypyr, and chlorpyrifos. High mortality was observed in all treatments containing fipronil, but none after exposure to bifenthrin, tefluthrin, λ-cyhalothrin, chlorantraniliprole, spirotetramat, spinosad, or low rates of cyazypyr. Combining thiamethoxam with fipronil or a high rate of chlorpyrifos decreased the toxicity of the second compound. These findings largely explain why we observe stand protection without wireworm population reduction in efficacy studies with wheat seed treated with various pyrethroid and neonicotinoid insecticides, and suggest a similar result for other insecticides that only induce temporary morbidity. This bioassay allows for rapid screening of insecticides proposed for wireworm management before these are evaluated in labour-intensive and costly field trials. [ABSTRACT FROM AUTHOR]

Two exotic European click beetle species, Agriotes obscurus and Agriotes lineatus, were introduced into the lower Fraser valley of British Columbia over a century ago, and are now predominant pests of a number of arable crops. A semiochemical-based method of monitoring both species has been developed as a part of an integrated pest management plan, and there is interest in mass trapping with pheromones as a management tool. A. obscurus females produce primarily geranyl octanoate (G8) and geranyl hexanoate (G6), while A. lineatus females produce both G8 and geranyl butanoate (G4). The current studies examined the possibility of using a blend of G8, G6, and G4 components in a single lure to trap both species simultaneously. A blended G8, G6 and G4 lure in a 1:1:1 ratio was, on average, 1.42 times more attractive to A. lineatus males than standard A. lineatus pheromone lures, but caught only 0.24 times the number of A. obscurus in standard A. obscurus traps. Blended traps, therefore, are effective for monitoring and mass trapping of A. lineatus, but only for detection of A. obscurus. [ABSTRACT FROM AUTHOR]

Belowground herbivores impact plant performance, thereby inducing changes in plant community composition, which potentially leads to cascading effects onto higher trophic levels and ecosystem processes and productivity. Among soil-living insects, external root-chewing generalist herbivores have the strongest impact on plants. However, the lack of knowledge on their feeding behaviour under field conditions considerably hampers achieving a comprehensive understanding of how they affect plant communities. Here, we address this gap of knowledge by investigating the feeding behaviour of Agriotes click beetle larvae, which are common generalist external root-chewers in temperate grassland soils. Utilizing diagnostic multiplex PCR to assess the larval diet, we examined the seasonal patterns in feeding activity, putative preferences for specific plant taxa, and whether species identity and larval instar affect food choices of the herbivores. Contrary to our hypothesis, most of the larvae were feeding-active throughout the entire vegetation period, indicating that the grassland plants are subjected to constant belowground feeding pressure. Feeding was selective, with members of Plantaginaceae and Asteraceae being preferred; Apiaceae were avoided. Poaceae, although assumed to be most preferred, had an intermediate position. The food preferences exhibited seasonal changes, indicating a fluctuation in plant traits important for wireworm feeding choice. Species- and instar-specific differences in dietary choice of the Agriotes larvae were small, suggesting that species and larval instars occupy the same trophic niche. According to the current findings, the food choice of these larvae is primarily driven by plant identity, exhibiting seasonal changes. This needs to be considered when analysing soil herbivore-plant interactions. [ABSTRACT FROM AUTHOR]

A study was conducted to determine whether arrays of pheromone traps could be used to reduce populations of male Agriotes obscurus ( AO) and Agriotes lineatus ( AL) adults in a confined nonfarmed habitat (grassy dyke)., Traps placed 3 m apart in 15 × 2 arrays captured significantly more AL than AO, although the trap catch varied with location for both species and was inversely related to the number of nearby competing traps., Models of beetle movement indicated that a considerable proportion of males ( AL: 18.4-71.8%; AO: 35.0-58.3%) collected in the arrays had moved in from elsewhere and that AL beetles are more active than AO beetles. AL beetles frequently entered AO traps unless both trap types were present in the array, whereas AO rarely entered AL traps., Concurrent catches in pitfall traps placed inside and outside pheromone trapping zones indicated the trap arrays significantly reduced male (but not female) AO and AL beetles inside their respective arrays, that AO traps reduced AL beetles in AO arrays, and that both AL and AO traps could potentially reduce the number of mating pairs in these arrays., The implications of these results in determining the efficacy of this approach as a click beetle management approach are discussed. [ABSTRACT FROM AUTHOR]

Click beetles, the adult stage of wireworms, will enter fields of their preferred hosts (i.e., grasses, pasture, and cereals) from various reservoir habitats, and lay eggs which give rise to wireworm problems in subsequent years. To prevent click beetles, Agriotes obscurus, from immigrating into fields, a portable trench barrier composed of an extruded, PVC plastic trough was evaluated in 2001 in Agassiz, British Columbia, Canada. Plots of wheat or bare ground that were surrounded by trenches had significantly lower numbers of males in pheromone traps and females in pitfall traps relative to non-trenched plots. Exclusion was more pronounced in the first part of the study (about 75 % reduction) than later in the study (30-42 %), likely due to gradual within plot emergence of overwintered beetles and/or flight activity. The potential for use of exclusion devices for click beetle control and future directions for research are discussed. [ABSTRACT FROM AUTHOR]

We discuss the effect of the pyrethroid insecticide bifenthrin incorporated into soil at 100, 200, and 300 g AI/ha on late-instar larvae of the dusky wireworm, Agriotes obscurus (Coleoptera: Elateridae), and present a method of assessing wireworm health and mobility over time. Wireworms became moribund within 1 h of placement in soil amended with bifenthrin at all rates. After 2 weeks of morbidity in amended soils, wireworms recovered within 7 days of being placed in clean soil. A considerable proportion (0.13-0.93) of wireworms placed in amended soil moved to the soil surface and remained there for 2 weeks or more in a moribund state; wireworms transferred to clean soil no longer moved to the soil surface. Eight distinct mobility categories were observed and are described, and a new method for assessing wireworm health and mobility over time is discussed. [ABSTRACT FROM AUTHOR]

1 The dispersal abilities of agrioted beetles, serious pests on a variety of crops, are poorly known under natural conditions. This hampers their control. We used, for the first time, a stable isotope approach to assess dispersal of adult Agriotes obscurus in arable land. 2 After a diet switch from a C3- to a C4-plant, carbon isotope ratios of A. obscurus larvae significantly changed towards the isotopic signature of the new diet. Moreover, the larval δ13C signatures were transferred to the wing covers of the adult beetles with little distortion. 3 To assess the dispersal abilities under natural conditions, pheromone traps, lured for Agriotes sp., were installed at two study sites in Western Austria. Each site comprised a maize field (= C4-plant) and adjacent C3-grasslands with traps established along a transect of increasing distance to the maize. 4 δ13C signatures of wing covers revealed that adult male A. obscurus were able to migrate at least 80 m, which was the maximum distance that dispersal could be traced in the present study. The dispersal behaviour might have been influenced by site-specific factors. 5 The results obtained demonstrate a higher potential of adult male Agriotes to disperse than previously assumed. Moreover, the combination of pheromone trapping and stable isotope analysis proved to be an effective approach to study insect movement and dispersal in arable systems harbouring C3- and C4-crops. [ABSTRACT FROM AUTHOR]

1 Wireworms, the soil dwelling larvae of click beetles, Agriotes spp., have recently become a more prevalent pest of potatoes. The present study investigated whether potato varieties showed variable susceptibility to wireworm herbivory, and also tested whether increased susceptibility was associated with lower concentrations of glycoalkaloids. Twelve varieties were originally screened across a range of experimental scales, including laboratory and tunnel experiments and a large-scale field trial involving over 2000 tubers. 2 In laboratory no-choice tests, Maris Peer, Marfona and Rooster varieties were significantly more susceptible to wireworm attack, with 63% of tubers showing damage, compared with just 15% of the less susceptible varieties of King Edward, Nadine and Maris Piper. There was also greater tissue consumption and weight gain when wireworms were reared on the most susceptible varieties. 3 In choice tests, wireworms showed a significant preference for those varieties previously identified as being the most susceptible to wireworm herbivory (4.2 holes per tuber) compared with the least susceptible (1.2 holes per tuber). Similar patterns of susceptibility were seen in the field trial, although there was generally more variation in susceptibility. 4 In a tunnel experiment, Marfona and Maris Peer were significantly more susceptibile to wireworm attack (47% of tubers showing damage) compared with Nadine, King Edward and Maris Piper (27% of tubers showing damage). Although Nadine, in particular, had the highest glycoalkaloid concentrations (309.33 mg/kg) and lowest amounts of wireworm herbivory, the relationship between susceptibility and glycoalkaloid concentrations was weak, suggesting that this is unlikely to be the sole mechanism underpinning varietal susceptibility. [ABSTRACT FROM AUTHOR]

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A soil-less bioassay arena to test repellency of wireworms (A. obscurus) to insecticides and carrier solvents is described. The bioassay and variables measured distinguish between shorter-range (contact and/or volatile) and longer-range (volatile) repellency. Wireworm positions are recorded every 3 s for 20 min, and average speed, rate of slowing, and longer- and shorter-range repellent behaviors calculated. Shorter-range repellency is determined with a Wireworm Repellency Score (WRS, range 0-100), calculated before contact and after contact with test chemicals. Of two carrier solvents tested, wireworms were strongly repelled by acetone (WRS = 57) but not by water (WRS = 1) when introduced to the bioassay arenas immediately after chemical inoculation. When bioassay arenas were assembled/sealed 2 min after inoculation, acetone elicited no repellency (WRS = 2). When dissolved in acetone in bioassays assembled with a 2-min delay, imidacloprid, chlorpyrifos, lindane, and tefluthrin elicited slight to moderate repellency at the highest concentrations tested (WRS = 30, 48, 42, and 49, respectively). Both longer- and shorter-range repellency increased over the duration of the observation period for lindane and tefluthrin, and shorter-range repellency also increased over the duration of the observation period for chlorpyrifos. Removal of volatiles in the bioassay arena by vacuum considerably affected wireworm movement in the arena, with the repellency elicited by acetone and lindane being significantly reduced. Clothianidin elicited no longer- or shorter-range repellency. [ABSTRACT FROM AUTHOR]

Ten insecticides representing seven chemical groups were applied at various concentrations topically by using a Potter Spray Tower to evaluate their relative toxicities on the European wireworm Agriotes obscurus L. (Coleoptera: Elateridae). Wireworms were stored at 15°C after exposure to organophosphate (OP) (chlorpyrifos, diazinon), pyrethroid (tefluthrin), thianicotinoid (thiamethoxam, clothianidin), chloronicotinoid (imidacloprid, acetamiprid), phenyl pyrazole (fipronil), organochlorine (lindane), and spinosyn (spinosad) insecticides, and their postapplication health was evaluated weekly for up to 301 d. LC50, LC90, LT50, and LT90 values were calculated for each chemical except acetamiprid, and compared with those of lindane, clothianidin, and chlorpyrifos. Wireworms exposed to OPs died or recovered more quickly (LT50 < 20 d, LT90 < 50 d), than those exposed to all other insecticides tested except tefluthrin (LT50 = 25.5 d, LT90 66.5 d). Wireworms exposed to sublethal concentrations of all neonicotinoids quickly became moribund after application but made a full recovery. Wireworms exposed to fipronil at concentrations near the LC90 value showed no intoxication symptoms for up to 35 d, and they did not recover after symptoms developed. For each chemical, increasing the concentration increased the time required for wireworms to recover but decreased the time required to kill wireworms. Fipronil was highly toxic to wireworms (LC50 = 0.0001%), but acetamiprid (LC50 = 1.82%), imidacloprid (LC50 = 0.83%), tefluthrin (LC50 0.23%), diazinon (LC50 = 0.54%), and spinosad (LC50 = 0.51%) were not. The toxicity of both clothianidin (LC50 = 0.07%) and thiamethoxam (LC50 = 0.17%) were similar to those of lindane (LC50 = 0.06%) and chlorpyrifos (LC50 = 0.10%). [ABSTRACT FROM AUTHOR]

A bioassay for observing wireworm behavior in soil is described. The bioassay permits analysis of orientation, feeding, repellency, and postcontact toxicity behaviors of wireworms in response to insecticide-treated wheat seeds. Wireworm positions were recorded every 5 mm for 3 h, and the time required to orient to and contact seeds, and the duration of individual feeding events, was calculated. Both avoidance (before contact with seeds) and repellency (after contact) were quantified. A high proportion of Agriotes obscurus (0.95), Limonius canus (1.00), Ctenicera pruinina (0.80), Melanotus communt.s/dietrichi (0.80), and Hypolithus sp. (0.70) larvae contacted untreated wheat seeds and began feeding within 120 mill when seeds were preincubated for 60 mm in soil with 20% moisture. A smaller proportion of A. obscurus contacted seeds if seeds were not incubated in the bioassay before wireworm introduction (0.80) or in soil with 10% moisture (0.65). L. canus larvae required a significantly shorter time (25.3 mm) to contact seeds if seeds were incubated for 60 mm than if seeds were not incubated before wireworm introduction (43.1 mi. Wireworms exposed to untreated seeds and seeds treated with the fungicide Dividend XLRTA fed normally (i.e., sustained feeding for at least 60 mm), but a significant proportion of wireworms exposed to seeds treated with Tefluthrin 20 CS (containing the synthetic pyrethroid tefluthrin) fed for 15 mill or less and were subsequently repelled. Wireworms exposed to Vitavax Dual (containing the organochlorine lindane) were not repelled after feeding and showed symptoms of illness for up to 28 d before making a full recovery'(89%) or dying (11%). [ABSTRACT FROM AUTHOR]

Abstract: Larvae of Agriotes obscurus L. and A. lineatus L. were placed in tubs of soil collected from British Columbia (BC) and flooded with purified water for 4, 7, 11, 14, 18, 25, 39, or 53 days at 5, 10, 15, or 20°C. Wireworms submerged at high temperatures died more quickly than those submerged at low temperatures, and wireworms in flooded Delta soil died more quickly than those in flooded Agassiz soil. Soil analysis suggests that soil salinity may affect the effectiveness of flooding as a control strategy. Flooding in fall or summer (higher temperatures) would likely provide more effective control of wireworm populations than flooding in winter. [Copyright &y& Elsevier]

Agriotes obscurus (L.) wireworms assembled in increasing numbers at rows of treated (Agrox DL Plus seed treatment) and untreated wheat, Triticum aestivum L., planted at increasing densities (0,0.15,0.30, and 0.60 seeds/cm). In treated wheat plots at all planting densities, no wireworm damage to seedlings was apparent, and total wireworms taken in core samples in wheat rows increased according to the asymptotic equation y = B0(1 -e-Blx), where B0 is the asymptote, Bi is the slope of the initial rise, and x is the seeding density. The number of dead wireworms in treated plots increased linearly and intercepted the asymptotic models (theoretical point at which 100% mortality of assembled population occurs) at 0.95 seeds/cm on 11 June and 1.14 seeds/cm on 18 June 1996. Untreated wheat at all densities planted had severe wireworm damage and significantly reduced stand. Populations that had assembled at the surviving untreated wheat were fewer than in the treated wheat plots, and although increasing with seeding density, did not follow the asymptotic model. The data suggest that A. obscurus populations can be assembled and killed in fallowed fields in large numbers at treated trap crops of wheat over a 19-d period when planted in rows spaced 1 m apart at a linear seeding density of 1.5 seeds/cm. [ABSTRACT FROM AUTHOR]

Acute toxicities of three naturally occurring monoterpenoid essential oil constituents and the essential oil of rosemary were tested against late instars of Agriotes obscurus (L.) (Coleoptera: Elateridae). Both contact and volatile toxicities of thymol, citronellal, eugenol, and rosemary oil were determined. Also, phytotoxicity of these compounds was evaluated on corn germination and seedling development. Thymol had the greatest contact toxicity (LD50 = 196.0 μg/larva), whereas citronellal and eugenol were less toxic (LD50 = 404.9 and 516.5 μg/ larva, respectively). Rosemary oil did not show any significant contact toxicity, even at 1,600 μg/larva. In terms of volatile toxicity, citronellal was the most toxic to wireworm larvae (LC50 = 6.3 μg/cm³) followed by rosemary oil (LC5∅ = 15.9 μg/cm³), thymol (LC50 = 17.1 μg/cm³), and eugenol (LC50 = 20.9 μg/cm³). Thymol, eugenol, and citronellal significantly inhibited corn seed germination and development, whereas rosemary oil had only minimal phytotoxic effects. [ABSTRACT FROM AUTHOR]

Field experiments with four potato cultivars showed that there were significant differences in susceptibility to attack by wireworm, Agriotes obscurus. The two most susceptible cultivars had the lowest total glycoalkaloid (TGA) contents. Laboratory experiments with wireworms feeding on tuber slices demonstrated that regions characterized by a low sugar and a high glycoalkaloid concentration were avoided as feeding sites. Bio-assays with glycoalkaloids also showed that paper discs treated with a mixture of solanine and chaconine were avoided by wireworms. According to a forward stepwise regression analysis based on data from four cultivars and six regions of the tuber. TGA was the key factor in predicting larval feeding, accounting for 65% of the total variation. Differences in reducing sugar levels (fructose + glucose) explained an additional 13% of the variation. Differences in chlorogenic acid and sucrose levels added very little to the accuracy of the prediction. [ABSTRACT FROM AUTHOR]

Abstract: Tracking the movement of soil-living herbivores is difficult, albeit important for understanding their spatial ecology as well as for pest management. In this study the movement of Agriotes obscurus larvae between plots harbouring isotopically different plants was examined. Neither between maize and wheat nor between maize and grassland movement could be detected. These data suggest that Agriotes larvae rarely disperse between crops as long as local food supply is sufficient. Moreover, the current approach provides a new means to study the dispersal of soil invertebrates in situ. [Copyright &y& Elsevier]

Several Agriotes click beetle species are important pests of vegetables and field crops. Monitoring for beetles is generally done with pheromone-baited traps maintained in permanent locations. Since dispersal is mostly by walking, such traps may deplete populations around them, leading to underestimations of populations relative to nontrapped areas, and of concomitant risk of wireworm damage to nearby crops. We placed sets of five pitfall traps in field headland areas in 2015-2017, of which two were baited with Agriotes obscurus (L) or Agriotes lineatus (L) (Coleoptera: Elateridae) pheromone. Of these, one was maintained in a permanent location, while the other moved among the remaining positions. Traps were checked weekly over the emergence period. For A. obscurus, fixed and moving traps initially collected similar numbers, but the latter collected significantly more later in the season, indicating depletion around fixed traps. Depletion was most pronounced after a period of cold weather, and around the peak swarming period. Depletion observed for A. lineatus was not statistically significant. This indicates pheromone-baited traps used for walking insects can underestimate populations, but depletion rates vary with species and temperature and should be accounted for when traps are used to develop action thresholds or time control strategies., (© Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture, 2020. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)