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Populations of various economic species of wireworms are increasing in the key cereal crop production areas of Canada and the United States. To address this problem, seed treatments are under development that both provide crop protection and significantly reduce populations equivalent in effectiveness to the formerly used but now deregistered organochlorine lindane. Herein, we evaluated isocycloseram (PLINAZOLIN technology), the first isoxazoline (GABA-gated Chloride Channel Allosteric Modulator) agricultural insecticide, as a seed treatment for the protection of cereal crops from the sugarbeet wireworm, Limonius californicus (Mannerheim). In wheat and barley field trials conducted over 4 years under extreme wireworm pressure, isocycloseram applied as a seed treatment at 5.0-7.5 g AI/100 kg seed was as effective as or more effective than the current industry standard thiamethoxam at 20.0 g AI/100 kg seed in protecting crop stand and yield. Isocycloseram also reduced neonate wireworms (produced from eggs during the growing season) and resident wireworms (in the field at the time of planting) to levels expected from the formerly used seed treatment lindane., (© His Majesty the King in Right of Canada 2024. Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada.)

Larvae of two species of click beetle, Agriotes obscurus and Agriotes lineatus, are important pests of vegetable and field crops in both Europe and North America. Both species have been long and extensively studied, but to date little is known regarding the maturation and egg development of female beetles relative to their swarming periods. This knowledge is important for developing wireworm management tactics that target female beetles, as these would ideally eliminate the beetles before they oviposit. This paper is an attempt to address this knowledge gap. We dissected 2,450 female A. obscurus and 477 female A. lineatus collected in southwestern British Columbia in 2015-2020, and describe how their abdominal lipid content and number of mature eggs change during their swarming period. Based on the presence of mature and immature eggs, active ovarioles, and lipid content, we propose 6 consecutive beetle maturity stages. Beetles collected early in the season have high lipid content and no eggs. Over time, immature, then mature eggs appear and the lipid content decreases dramatically. Ovarioles are generally active throughout the swarming period, even when lipids are no longer present, suggesting that for these species egg laying may continue until the end of the season, and that fecundity depends both on a beetle's original lipid content at emergence, and subsequent diet., (© His Majesty the King in Right of Canada 2024. Reproduced with the permission of the Minister of Natural Resources Canada.)

Wireworms are primary pests of potatoes in Canada. Presently, the highly toxic organophosphate phorate (i.e., Thimet 20G) is the only effective insecticide in use in Canada. As such, there is an urgent need for novel alternative treatments that provide competitive tuber blemish protection and wireworm reduction with a safer human and environmental portfolio. Herein we evaluated broflanilide, a novel meta-diamide insecticide for both tuber protection and wireworm mortality. When evaluated in field trials in Agassiz, British Columbia over 6 yr, broflanilide applied as a seed piece treatment (SPT) to mother tubers at 1.5-2.0 g AI/100 kg seed (approx. 50 g AI/ha), or as an in-furrow spray (IFS) at 0.23-0.25 g AI/100 m row (approx. 25 g AI/ha) was as effective at reducing blemishes to daughter tubers by wireworms (Agriotes obscurus) as phorate (Thimet 20G at 3230 g AI/ha), bifenthrin (Capture 2EC IFS at 300 g AI/ha) and clothianidin (Titan ST at 312.5 g AI/ha). In addition, broflanilide SPT and IFS applied at the above rates reduced resident wireworms (in the field at the time of planting) by 95.4-99.0% and neonate wireworms (produced from eggs laid during the growing season) by 98.1-100%. Similar results were obtained when broflanilide IFS (nonsystemic) was paired with clothianidin SPT (systemic) for broad-spectrum potato insect pest control. Strategies for the use of broflanilide on wheat (e.g., Teraxxa F4) in rotation with potatoes (Cimegra), both registered in Canada in 2020 are discussed., (© Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture and Agri-Food Canada, 2022.)

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., (© Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture and Agri-Food Canada, 2022.)

We present findings of a general survey of pest wireworms in Alberta, Saskatchewan, and Manitoba conducted from 2004 to 2019; the first such survey of the Canadian Prairie provinces since that published by Glen et al. (1943). Samples were collected from 571 farmland locations where crop damage from wireworms was observed or suspected, and a total of 5,704 specimens (3,548 larvae, 2,156 beetles) were identified. Most specimens (96.9%) were identified as Hypnoidus bicolor (3,278), Selatosomus aeripennis destructor (1,280), Limonius californicus (842), and Aeolus mellillus (125). This suggests that H. bicolor has replaced S. a. destructor as the predominant species and that the relative importance of L. californicus as a pest species has increased since earlier reports. Despite the relatively small number of specimens collected per location (approx. 10), H. bicolor and S. a. destructor, and S. a. destructor and L. californicus were frequently collected at or near the same location (within 1 km). We provide species records and incidence of co-occurrence at different spatial scales, discuss potential reasons for and implications of shifts in species composition, implications of species co-occurrence for managing wireworm pests in crop production, and outline pertinent research needs. A path analysis approach used to correlate incidence of the main species with various soil characteristics indicated that organic matter, cation exchange capacity, and water retention capacity all had a significant species-specific influence on wireworm presence., (© Her Majesty the Queen in Right of Canada, as represented by the Minister of Natural Resources Canada, 2021.)

Following the deregistration of lindane, several neonicotinoid insecticides have been registered as seed treatments for controlling wireworms in cereal crops. Unlike lindane, which did both, neonicotinoids provide crop protection but do not reduce wireworm populations. Hence populations of various economic species are growing in key wheat production areas of the United States and Canada, and there is a need for novel seed treatments that match the efficacy of lindane. Herein we evaluated broflanilide, a novel GABA-gated Cl- channel allosteric modulator that differs from the cyclodienes (e.g., lindane) in that it binds to a unique site in the GABA receptor. As such, broflanilide confers a new mode of insecticidal action (Group 30 MOA), and is the first meta-diamide insecticide developed. When evaluated in field trials over 7 yr at various rates, broflanilide at 5.0 g [AI]/100 kg wheat seed was as effective at protecting wheat stand from wireworm (Agriotes obscurus) injury as the current industry standard thiamethoxam at 20-30 g [AI]/100 kg seed. In addition, broflanilide at 5.0 g reduced neonate wireworms (produced from eggs laid in established wheat during the growing season) and resident wireworms (in the field at time of planting) by 73.1 and 81.1%, respectively, which is comparable to that reported for the previous industry standard lindane (75.3 and 57.6%, respectively). These studies show that broflanilide at 5.0 g [AI] will provide consistent wheat stand protection (equal to thiamethoxam at 20-30 g [AI]), and A. obscurus wireworm population reduction (equal to lindane at 59 g [AI]), and will do so at far lower dosages per hectare., (© Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture, 2021.)

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.)

Wireworms are important economic pests that attack the seeds and roots of numerous vegetable and field crops worldwide. A 5-yr study was conducted in the main agricultural regions of the province of Quebec (Canada), to identify and characterize the wireworm communities (Coleoptera: Elateridae) that occur in fields planted with economically important crops (maize, soybean, cereals, canola, and grasslands). Bait traps were used to collect wireworms each spring from 2011 to 2015. More than 600 sites were sampled in total, involving ca. 14,000 traps. Wireworms were found in 69% of the sites and 73% of the traps. A total of 6,014 wireworms were collected and identified to genus, or to species when possible. The results show that nine genera occur in Quebec and that Hypnoidus abbreviatus (Say) is currently the most abundant species in arable land in Quebec, representing 72% of all collected wireworms. The other genera collected were Melanotus (8% of all wireworms collected), Ampedus (7%), Limonius (6%), and Agriotes (4%). Wireworms from the genera Aeolus, Dalopius, Hemicrepidius, and Oestodes constituted ca. 3% together. The predominance of H. abbreviatus appeared to be specific to Quebec compared with the other Canadian provinces and the rest of North America. We observed differences in the relative abundance of wireworm genera among the agricultural regions sampled. However, no effect of current and preceding crops was observed in this study. Our results suggest that integrated pest management strategies for managing wireworms in Quebec fields should take into consideration the species present in each agronomical region., (© The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

At the time of this research, there were only two insecticides registered for control of cabbage maggot, Delia radicum L., in rutabaga in Canada, one of which (diazinon) will be deregistered by 2017, and resistance having been reported in some areas for the other (chlorpyrifos). To screen for chemistries to replace these organophosphates, and obtain efficacy data comparable between key vegetable brassica production areas in Canada, four small plot field studies were conducted concurrently in British Columbia, Saskatchewan, Ontario, and Quebec in 2009. These studies followed standardized protocols for seeding, application of insecticide drenches, sampling and damage assessment, and generally tested the same products. Of the insecticides evaluated, none provided maggot control comparable with the industry standard, chlorpyrifos. However, cyantraniliprole (Cyazypyr 200SC; registered in 2015 as Verimark) applied at 3 g AI (15.0 ml product)/100 m row of seeded rutabagas consistently provided the next highest reduction in % culls, suggesting the efficacy of this chemical may be improved if used at higher rates. The results of these studies are discussed in the context of current literature on D. radicum management in rutabaga. Future management strategies are also discussed, including a transplant plug treatment approach for increasing the dosage per plant and efficacy of chemistries such as Cyazypyr 200SC in the field., (© Crown copyright 2016.)

Wireworms, the larvae of click beetles (Coleoptera: Elateridae), have had a centuries-long role as major soil insect pests worldwide. With insecticidal control options dwindling, research on click beetle biology and ecology is of increasing importance in the development of new control tactics. Methodological improvements have deepened our understanding of how larvae and adults spatially and temporarily utilize agricultural habitats and interact with their environment. This progress, however, rests with a few pest species, and efforts to obtain comparable knowledge on other economically important elaterids are crucial. There are still considerable gaps in our understanding of female and larval ecology; movement of elaterids within landscapes; and the impact of natural enemies, cultivation practices, and environmental change on elaterid population dynamics. This knowledge will allow generation of multifaceted control strategies, including cultural, physical, and chemical measures, tailored toward species complexes and crops across a range of appropriate spatial scales.

The efficacy of various insecticides and application methods in protecting potatoes from wireworm (Agriotes obscurus L.) damage as well as reducing wireworm populations was studied over 5 yr in Agassiz, British Columbia. Protection from wireworm damage was measured by the number of blemishes to daughter tubers, and effects on wireworm populations were measured by sampling soil around seed potatoes and/or by bait traps the following spring. Organophosphates registered for wireworm control in the United States and/or Canada (phorate and chlorpyrifos), significantly reduced blemishes to tubers by, respectively, 92.2 and 90.2%, and populations of large (> or = 9 mm long = 'resident') wireworms by 83.4 and 71.0% relative to controls. Similar reductions in smaller (< 9 mm long = 'neonate') wireworms were also observed. Neonicotinoids (imidacloprid, clothianidin, and thiamethoxam) tested as seed piece treatments at approximately 12.5 g active ingredient/100 kg potato seed reduced blemishes by, respectively, 19.1, 71.6, and 90.6%, but resident wireworms were only reduced by, respectively, 22.0, 29.1, and 51.8%. Significant mortality of neonates was not observed with any neonicotinoid treatment. With the possible exception of thiamethoxam, where significant reduction in resident wireworms occurred, it is likely that the blemish protection provided without significant wireworm mortality with imidacloprid and clothianidin treatments was because of long-term wireworm intoxication followed by population recovery. The phenyl pyrazole, fipronil, applied as an in-furrow spray reduced blemishes by 94.3%, and resident wireworm populations could not be detected in plots the following spring. Neonates were reduced by 93.3%, indicating excellent residual conotrol had occurred with fipronil. These studies indicate that tuber protection by fipronil and currently registered organophosphates is likely because of significant early season mortality of wireworms, whereas neonicotinoids generally provide control through long-term morbidity without high levels of mortality occurring.

The efficacy of various insecticidal seed treatments in protecting wheat, Triticum aestivum L., from wireworm damage as well as reducing wireworm (Coleoptera: Elateridae) populations was studied over 3 yr. Protection from wireworm damage was measured by postplanting stand counts, and effects on wireworm populations were measured by within-row core samples and by bait traps placed in plots the following spring. The effects of treatments on populations of larger wireworms already present at planting were distinguished from their effects on neonate wireworms produced that growing season. Neonicotinoid seed treatments (imidacloprid, clothianidin, and thiamethoxam) provided excellent wheat stand protection, likely through prolonged wireworm intoxication, but populations of larger and neonate wireworms were not significantly reduced in bait traps the following spring. The pyrethroid tefluthrin, applied to seed with and without a neonicotinoid insecticide (thiamethoxam), provided excellent crop protection, but populations of wireworms also were not significantly reduced. This and additional laboratory data suggest that wheat stand establishment provided by tefluthrin is due to a combination of repulsion and short term morbidity events. The phenyl pyrazole fipronil provided excellent crop protection, and populations of both larger and neonate wireworms could not be detected in plots the following spring. The previously registered organochlorine lindane, although reducing wireworm feeding, was phytotoxic in 2 of 3 yr. Next to fipronil, lindane was the most consistent seed treatment in reducing populations of larger and neonate wireworms. These studies indicate that stand and yield protection provided by contemporary wheat seed treatments cannot automatically be equated with wireworm population mortality. This is an important consideration when choosing a suitable seed treatment to replace lindane, which historically provided both stand protection and wireworm reduction, and did not have to be applied every year.

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.

During an insecticide toxicity study involving field-collected dusky wireworm, Agriotes obscurus (L.) (Coleoptera: Elateridae), wireworms exposed dermally to six classes of insecticides exhibited characteristic transitional symptoms of toxicity. These symptoms, collectively termed "morbidity," were categorized as "writhing," "leg and mouthpart movements," or "mouthpart-only body movements." These symptoms could persist for long periods, depending on insecticide and dose, with morbid wireworms ultimately recovering or dying. Additional LC50 and LD50 toxicity studies showed that these stages of morbidity also occurred in four other wireworm species, notably Agriotes sputator (L.), Limonius canus LeConte, Ctenicera pruinina (Horn), and Ctenicera destructor (Brown). In addition, all species exposed dermally to clothianidin moved in significant numbers to the surface of soil in posttreatment holding cups. This movement was not observed when these species were exposed to chlorpyrifos or the control solvent. These findings suggest that toxicity trials involving wireworms should include observations on morbidity, and the duration of trials should continue until symptoms of morbidity cease. The long-term morbidity and potential recovery or death of wireworms exposed to certain insecticides has implications for how laboratory and field studies can be better designed and interpreted in the future.

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 degrees 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 oflindane (LC50 = 0.06%) and chlorpyrifos (LC50 = 0.10%).

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 min 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 communis/dietrichi (0.80), and Hypolithus sp. (0.70) larvae contacted untreated wheat seeds and began feeding within 120 min when seeds were preincubated for 60 min 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 min) to contact seeds if seeds were incubated for 60 min than if seeds were not incubated before wireworm introduction (43.1 min). Wireworms exposed to untreated seeds and seeds treated with the fungicide Dividend XLRTA fed normally (i.e., sustained feeding for at least 60 min), but a significant proportion of wireworms exposed to seeds treated with Tefluthrin 20 CS (containing the synthetic pyrethroid tefluthrin) fed for 15 min 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%).

A prototype ground-based pheromone trap design, baited with various pheromone lures, was field tested for effectiveness in trapping male Agriotes obscurus and Agriotes lineatus click beetles in British Columbia. Pheromone dispensers containing geranyl octanoate and geranyl hexanoate in a 1:1 ratio caught the greatest numbers of A. obscurus, whereas those containing geranyl octanoate and geranyl butanoate in a 9 or 10:1 ratio caught high numbers of A. lineatus. Some differences in A. obscurus attraction to traps were observed between dispensers according to the manufacturer and the number of dispensers deployed in traps. The trap design and optimal pheromone dispensers tested would be suitable for monitoring or surveying A. obscurus and A. lineatus populations in North America.

Counts of green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), in potato, Solanum tuberosum L., fields were used to evaluate the performance of the sampling plan from a pest management company. The counts were further used to develop a binomial sampling method, and both full count and binomial plans were evaluated using operating characteristic curves. Taylor's power law provided a good fit of the data (r2 = 0.95), with the relationship between the variance (s2) and mean (m) as ln(s2) = 1.81(+/- 0.02) + 1.55(+/- 0.01) ln(m). A binomial sampling method was developed using the empirical model ln(m) = c + dln(-ln(1 - P(T))), to which the data fit well for tally numbers (T) of 0, 1, 3, 5, 7, and 10. Although T = 3 was considered the most reasonable given its operating characteristics and presumed ease of classification above or below critical densities (i.e., action thresholds) of one and 10 M. persicae per leaf, the full count method is shown to be superior. The mean number of sample sites per field visit by the pest management company was 42 +/- 19, with more than one-half (54%) of the field visits involving sampling 31-50 sample sites, which was acceptable in the context of operating characteristic curves for a critical density of 10 M. persicae per leaf. Based on operating characteristics, actual sample sizes used by the pest management company can be reduced by at least 50%, on average, for a critical density of 10 M. persicae per leaf. For a critical density of one M. persicae per leaf used to avert the spread of potato leaf roll virus, sample sizes from 50 to 100 were considered more suitable.

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, B1 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.

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 microg/larva), whereas citronellal and eugenol were less toxic (LD50 = 404.9 and 516.5 microg/larva, respectively). Rosemary oil did not show any significant contact toxicity, even at 1,600 microg/larva. In terms of volatile toxicity, citronellal was the most toxic to wireworm larvae (LC50 = 6.3 microg/cm3) followed by rosemary oil (LC50 = 15.9 microg/cm3), thymol (LC50 = 17.1 microg/cm3), and eugenol (LC50 = 20.9 microg/cm3). Thymol, eugenol, and citronellal significantly inhibited corn seed germination and development, whereas rosemary oil had only minimal phytotoxic effects.

The persistence and retention of active ingredients in granules of Thimet 15G (phorate 15% by weight), Dyfonate 10G (fonofos 10% by weight), Counter 15G (terbufos 15% by weight), and Furadan 10G (carbofuran 10% by weight) were determined in silt loam and organic muck agricultural soils typical of the lower Fraser River valley (BC, Canada). In June 1995, treatment bags made of polyester cloth (7.5 x 7.5 cm) containing granules of a single insecticide, either alone or with soil, were placed during spring planting in the bottom of the furrow and retrieved periodically until April 1996. The parent component of each insecticide declined monotonically except for carbofuran (logistic decline). In the silt loam (organic muck) soil, the average June-to-October first-order rate constants and half-lives were 0.009 (0.010)/d and 80 (71) d for fonofos, 0.012 (0.009)/d and 58 (82) d for phorate, and 0.032 (0.015)/d and 21 (47) d for terbufos; the half-life of carbofuran was 129 (97) d. By December, the average amounts of fonofos and phorate in silt loam (organic muck) were 26% (range: 17-40%; 14% [range: 3.4-21%]) and 21% (range: 15-30%; 10% [range: 5.0-24%]) of the initial amounts of active ingredients measured at time zero, respectively. By April, the percentages dropped to 16% (range: 7.8-24%; 2.3% [range: 0-7.7%]) and 7.3% (range: 1.9-25%; 0.6% [range: 0-1.9%]). During this period, about 95% of the active ingredients were granule bound, the rest remaining in the bag. Only low levels of terbufos and carbofuran persisted in both soils from December to April of the following year. Results indicate an enhanced probability for poisoning of waterfowl and raptors because of the high levels of active ingredients retained on granules of all four insecticides in both soils in the fall. The risk of acute poisoning by phorate and fonofos continued though the winter.

Experiments were conducted to test a portable trench barrier composed of an extruded, UV-retarded, PVC plastic trough, designed to allow Colorado potato beetles, Leptinotarsa decemlineata (Say), to enter and become trapped and killed inside. Tests demonstrated that the portable plastic trenches were effective as barriers to Colorado potato beetles as they walked into tomato, Lycopersicon esculentum Mill., fields from overwintering sites in the spring. In field tests, plots that were protected by portable trench barriers had significantly fewer beetles per tomato plant, and lower levels of defoliation. Tomato yields in plots that were protected by portable trench barriers were similar to yields in plots that were protected by insecticide sprays, and significantly higher than plots where beetles were not controlled.

The effect of crop rotation on populations of tuber flea beetle, Epitrix tuberis Gentner, in potatoes was investigated using data supplied by an integrated pest management (IPM) company and Geographic Information System software and conventional statistical methods. Using combined 1995 and 1996 data, beetles of the overwintered and F1 generations in both the interior and edges of potato fields showed a significant linear increase with an increase in the preceding consecutive years (0, 1, and 2 years) that the current years' crop was planted to potatoes. Populations were significantly higher in nonrotated fields compared with rotated fields. Both the percentage of the cropping region requiring insecticidal control of tuber flea beetles and the cost of insecticides per hectare of potatoes grown increased linearly with an increase in the number of previous years planted to potatoes. Not practicing crop rotation resulted in a 4.2-7.3% increase in the cropping region requiring insecticidal control of tuber flea beetles. The cost of controlling beetles in potato fields planted to potatoes for 3 consecutive years was up to $20/ha greater than potatoes rotated from the preceding year. Beetle counts from the interior of rotated potato fields never exceeded threshold levels when field edges also were below threshold. It is concluded that sampling of overwintered beetles in interior sites of rotated fields could be abandoned, and only 1 monitoring scout rather than 2 would be necessary to monitor a field during this time. From these results, we concluded that rotating potato crops would reduce spray costs to the farmer and monitoring costs to IPM companies.