Limonius Canus Research Articles

Limoniic Acid - Major Component of the Sex Pheromones of the Click Beetles Limonius canus and L. californicus.

Wireworms, the larvae of click beetles (Coleoptera: Elateridae), are soil-dwelling insect pests inflicting major economic damage on many types of agricultural crops worldwide. The objective of this work was to identify the female-produced sex pheromones of the Pacific Coast wireworm, Limonius canus LeConte, and the sugarbeet wireworm, L. californicus (Mannerheim) (Coleoptera: Elateridae). Headspace volatiles from separate groups of female L. canus and L. californicus were collected on Porapak Q and analyzed by gas chromatography with electroantennographic detection (GC-EAD) and GC-mass spectrometry. GC-EAD recordings revealed strong responses from male L. canus and male L. californicus antennae to the same compound, which appeared below GC detection threshold. The structure of this candidate pheromone component was deduced from the results of micro-analytical treatments of extracts, retention index calculations on four GC columns, and by syntheses of more than 25 model compounds which were assessed for their GC retention characteristics and electrophysiological activity. The EAD-active compound was identified as (E)-4-ethyloct-4-enoic acid, which we name limoniic acid. In field experiments in British Columbia and Alberta, Canada, traps baited with synthetic limoniic acid captured large numbers of male Limonius click beetles, whereas unbaited control traps captured few. Compared to traps baited with the analogue, (E)-5-ethyloct-4-enoic acid, traps baited with limoniic acid captured 9-times more male L. californicus, and 6.5-times more male western field wireworms, L. infuscatus Motschulsky, but 2.3-times fewer male L. canus. Limoniic acid can now be developed for detection, monitoring and possibly control of L. californicus, L. infuscatus and L. canus populations.

Possible aversion learning in the Pacific Coast wireworm

The effects of carbon dioxide and the induction of morbidity on aversion learning in larvae of the Pacific Coast wireworm Limonius canus LeConte (Coleoptera: Elateridae) are discussed. Wireworms preconditioned by exposing them one or four times to odour of Tefluthrin 20SC and Dividend XLRTA [Syngenta Crop Protection (Canada), Inc., Canada] during the induction of temporary morbidity subsequently contact tefluthrin-treated wheat seeds in soil bioassays for as long as naive (i.e. not preconditioned) larvae but are repelled four to five-fold more frequently by Dividend-treated seeds in soil bioassays than naive wireworms, suggesting that wireworms are capable of associating a novel odour (i.e. Dividend) with morbidity but require a minimum of 10–15 min subsequent contact time with treated seeds before being repelled. Wireworms preconditioned by exposure to peppermint odour during the induction of morbidity are not subsequently repelled by peppermint odour in soil bioassays, suggesting that wireworms are either not capable of aversion learning or that the presence of a CO2 source and/or a suitable host plant may override a negative cue (i.e. peppermint odour). In studies conducted in the absence of soil, a host plant and CO2 production, wireworms are repelled slightly by droplets of 1.0% but not 0.1% peppermint oil. Previous exposure to peppermint odour or contact with peppermint oil-treated filter paper during one induction of morbidity does not increase the repellency of wireworms to 1.0% peppermint oil significantly. Repellency to 1.0% peppermint oil is almost eliminated when morbidity is induced five times in the absence of peppermint odour but is restored when peppermint odour is present during preconditioning. These findings suggest that wireworm sensitivity to repellent compounds decreases when repeatedly made moribund, although the results are not sufficient to conclude that wireworms are capable of associative learning.

Response of the Pacific Coast wireworm, Limonius canus, and the dusky wireworm, Agriotes obscurus (Coleoptera: Elateridae), to insecticide-treated wheat seeds in a soil bioassay

Larvae of the dusky wireworm, Agriotes obscurus, and the Pacific Coast wireworm, Limonius canus, were exposed to germinated, insecticide-treated wheat seeds in a soil-filled bioassay in 2005 and 2006. Position in the bioassay and contact and/or repellence behaviour towards the seeds were recorded every 5 min for 3 or 5 h. Wireworm health was recorded for 70 or 126 d after exposure. Seeds were treated with the fungicides Dividend XLRTA (difenoconazole, mefenoxam) or Raxil MD (tebuconazole, metalaxyl), and/or the insecticides Vitavax Dual (lindane), Poncho 600F (clothianidin), Cruiser 350FS (thiamethoxam), Admire 240FS (imidacloprid), Gaucho 480FL (imidacloprid), Tefluthrin 20CS (tefluthrin), or Tefluthrin-Cruiser combinations. Most wireworms (> 80%) came into contact with the seeds in all treatments. Wireworms generally remained in contact throughout the observation period in the control treatments (Dividend, Raxil, untreated seeds). Unless moribund, wireworms were repelled after brief (< 20 min) contact in all Tefluthrin treatments. Most wireworms recovered from contact-induced morbidity within 21 d and did not relapse, except L. canus exposed to Cruiser and some A. obscurus exposed to Gaucho and Admire. Wireworm mortality was low (< 50%) in all treatments except L. canus exposed to Cruiser at 15 and 30 g a.i. 100 kg-1 seed (60 and 75%, respectively). Mortality was significantly less important when L. canus larvae were exposed to Tefluthrin-Cruiser combinations than when exposed to Cruiser alone. We suggest that efficacy assessments of insecticides for wireworm control require direct observation of their behaviour and long-term post-exposure health assessments, and discuss the impact of repellence and/or morbidity elicited by insecticides on wireworm control in the field.

Transitional Sublethal and Lethal Effects of Insecticides After Dermal Exposures to Five Economic Species of Wireworms (Coleoptera: Elateridae)

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.

Transitional Sublethal and Lethal Effects of Insecticides After Dermal Exposures to Five Economic Species of Wireworms (Coleoptera: Elateridae)

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.

Effect of temperature on the morbidity and recovery of the Pacific Coast wireworm, Limonius canus, following contact with tefluthrin‐treated wheat seeds

AbstractLate instars of the Pacific Coast wireworm, Limonius canus (LeConte) (Coleoptera: Elateridae), were exposed to wheat seeds treated with tefluthrin at 10 g active ingredient/100 kg wheat seed, for 2 min, at 10, 15, 20, and 25 °C. All wireworms were moribund within 20 min of first exposure and recovered fully within 7 h. Morbidity induction time (i) decreased considerably as the temperature (t) was increased from 10 to 15 °C, but did not decrease further when the temperature was increased from 15 to 25 °C. For each temperature, induction time decreased as wireworm weight (w) increased, so that . A strong negative temperature coefficient was observed in wireworm recovery, the time required for recovery (r) after exposure decreasing as both temperature (t) and wireworm weight (w) increased, so that r = 1102.47(w)−0.1848 * e−0.1012t. The temperature at which wireworms contact insecticides in the field may significantly affect the induction and duration of morbidity, and determine whether wireworms will become moribund before they are repelled by tefluthrin. The ability of wireworms to recover from tefluthrin‐induced morbidity may seriously limit the efficacy of this insecticide in reducing wireworm populations in the field.

Soil Bioassay for Studying Behavioral Responses of Wireworms (Coleoptera: Elateridae) to Insecticide-Treated Wheat Seed

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%).

Gut bacteria associated with the Pacific Coast wireworm,Limonius canus, inferred from 16s rDNA sequences and their implications for control

A multitude of bacteria have been isolated from the guts of several insect species. Some of these have been modified to interfere with the development of the host insect or with the development and transmission of plant and animal pathogens transmitted by the host insect. We surveyed the gut flora of the Pacific Coast wireworm,Limonius canus LeConte, a serious pest of potato, at two sites in Oregon and Washington. Isolates were obtained from surface-sterilized triturated larvae by dilution plating on standard media. A rich diversity of species was found in 86 isolates, including spore-formers, non-spore-formers and aerobic and facultatively anaerobic species collected on four sampling dates at each location. Twenty-one of the isolates were identified to species based on rDNA sequence (nine distinct species). An additional 34 isolates were identified to genus from the sequence data while six isolates could be assigned only to family based on sequence comparisons. Twenty-seven additional isolates were identified to species (9), genus (17) or family (1) based on side-by-side morphological comparisons with isolates identified from rDNA sequence. The most frequently isolated bacterium wasBacillus megaterium, followed byRahnella aquatilis. A naturally occurring bacterium found in the gut and/or environment of a targeted insect that is modified to express toxins or other detrimental substances could provide certain advantages (such as persistence and recycling) over inundatively applied microbial control agents, particularly within soil habitats. The hypothesis that these species or others from the survey represent candidates for genetic modification to provide control options forL. canus is discussed.

Morbidity and recovery of the Pacific Coast wireworm, Limonius canus, following contact with tefluthrin‐treated wheat seeds

AbstractLate instars of the Pacific Coast wireworm, Limonius canus (LeConte) (Coleoptera: Elateridae), were exposed to wheat seeds treated with tefluthrin at 5, 10, 15, 20, or 30 g active ingredient (a.i.) per 100 kg wheat seed for 1, 2, 4, 8, or 16 min. All wireworms were moribund within 20 min of first exposure and recovered fully within 12 h. The time required for recovery (tr) after a single exposure increased with duration of exposure (e) and concentration (c), but decreased with wireworm weight (w), expressed as (tr)0.5 = 5.2812 + 0.9407e – 0.0259e2 + 0.1569c + 0.0254ec – 0.0174w – 0.0057ew. For wireworms exposed to treated seeds for 2 min, the time required for induction of morbidity decreased as concentration of tefluthrin increased and as wireworm weight decreased, expressed as (ti)0.5 = 2.613 – 0.039c + 0.018w, where ti is the induction time of morbidity, and c and w are as above. Wireworms re‐exposed to tefluthrin‐treated seeds after recovery from previous exposure were again moribund within 20 min of exposure, but recovery was significantly more rapid if the second exposure was 2, 4, 6, 8, 12, 18, 24, and 48 h after recovery from first exposure. Recovery from a second exposure was not significantly faster when the second exposure was 96 h after recovery from the first exposure. The ability of wireworms to recover from tefluthrin‐induced morbidity may seriously limit the efficacy of this insecticide in actually reducing wireworm populations in the field.

Comparison of Four Methods of Applying Insecticides for Control of Wireworms on Potatoes12

Preplant broadcast, at-plant sidedress, seed-piece furrow, and postemergence sidedress were tested as methods of applying insecticides for control of the Pacific Coast wireworm, Limonius canus LeConte, the sugarbeet wireworm, L. californicus (Mannerheim), and the Great Basin wireworm, Ctenicera pruinina (Horn), on potatoes. Differences in control were found for the various insecticides applied by the four methods at the three locations. Also, chemicals applied by a given method differed, depending on location. In general, all chemicals were as effective as fonofos, which was used as a standard, at all three locations, except carbofuran, chlorpyrifos G, and fensulfothion G. Carbofuran was tested at rates higher than those of fonofos, and chlorpyrifos G was tested at rates comparable to those of fonofos. Fensulfothion G, also used at rates higher than those of fonofos, gave control comparable to fonofos against a high density of wireworms, but less control against a low density. Comparison of the application methods with the standard showed that all four were equally effective against a low density of wireworms; however, against higher densities, at-plant sidedress was inferior to the other three methods, which were equally effective.

Chemical Control of Wireworms on Potatoes12

In 2 of 3 tests conducted to evaluate chemicals for control of the Pacific Coast wireworm, Limonius canus LeConte, and the Great Basin wireworm, Ctenicera pruinina (Horn), broadcast applications resulted in lower percentages of injured and culled tubers than did sidedress applications. In the 3rd test, there were no differences between broadcast, furrow, and at plant sidedress applications. Individual compounds differed in effectiveness depending on method of application in all 3 tests. Compounds that were very effective included N-2596 (S-(p-chlorophenyl)O-ethyl ethylphosphonodithioate), CGA 12223 (0-[5-chloro-1-(1-methylethyl)-lH-1,2,4-triazol-3-yl] O,O-diethyl phosphorothioate), and ethoprop. All 3 were as effective as fonofos (used as a standard) in reducing injury to tubers. Wireworm infestations (presence of wireworms or feeding on seed pieces and tubers) increased from time of planting until 16 wk; however, the highest number of wireworms per hill was found at 6 wk, but decreased thereafter. No difference in tuber injury was noted between 15–16 wk after planting and at harvest (20–21 wk).

Soil Incorporation of Insecticides for Control of Wireworms in Potato Land in British Columbia1

Experiments for the control of the Pacific Coast wireworm, Limonius canus LeConte, in a sandy loam at Grand Forks, and Agriotes obscurus (L.) in a silt loam at Agassiz, showed that potato tubers could be protected from damage by a single application of one of several insecticides. Fonofos G, at 5.6 kg AI/ha, broadcast evenly over the soil and rototilled to a depth of 10 cm was the most effective. Band treatments with the same material were slightly less effective. Two other compounds, terbufos and N 2596 (S-(p-chlorophenyl) O-ethylethane-phosphorodithioate) were nearly as good as fonofos. In the alkaline soils at Grand Forks, carbofuran gave only 50% control.

Pacific Coast Wireworm: Relationship Between Injury and Damage to Potatoes12

Data from 60 paired observations of total injury and official damage to potatoes caused by Limonius canus LeConte indicated that percentage ratings based on tuber counts or weights were directly comparable. The regression formula for converting injury ( I) to damage ( D) was D = 0.987 + 0.8361.

Sex Pheromones of the Pacific Coast Wireworm, Limonius canus12

Females of the Pacific Coast wireworm, Limonius canus LeConte, were found to contain 2 sex pheromones. One was identified as hexanoic acid. The other is a branched, unsaturated carboxylic acid, probably containing 10 carbon atoms.

Control of Wireworms on Summer Potatoes in Eastern Washington123

When granular carbofuran, Dyfonate® ( O -ethyl S -phenyl cthylphosphonodithioate), and parathion were applied in mid-March for control of the Great Basin wireworm, Ctenicera pruinina (Horn), and the Pacific Coast Wireworm, Limonius canus LeConte, on summer potatoes, band treatments at a rate of about 2.3 lb of toxicant per acre gave better average control with less variation than broadcast treatments with 4–8 lb of the same toxicant per acre. The reverse has been observed when similar treatments were applied in mid-April or later for control of these wireworms on fall potatoes.

Relative efficiency of three methods for chemical control of Pacific coast wireworms in potatoes

Data from six experiments with registered, nonpersistent chemical compounds for control of Pacific coast wireworm (Limonius canus Le-Conte) were combined to elucidate the relative efficiency of three types of treatments. The treatments were soil fumigation and band or broadcast applications of granular organophosphorus insecticides.

QUANTITATIVE RESPONSES OF MALES OF LIMONIUS CALIFORNICUS (COLEOPTERA: ELATERIDAE) TO FEMALE SEX PHEROMONE

AbstractIn adult virgin females of the sugar beet wireworm, Limonius californicus (Mannerheim), the sex attractant (recently identified as valeric acid) is found primarily in the fifth and sixth abdominal segments. Ether extracts of virgin females and of females that had been mated for not more than 4 hours prior to death contained the highest concentration of the attractant. The concentration of attractant in mated females decreased as the post-copulatory interval increased. In the laboratory maximum sexual response was elicited from males exposed to as little as 0.008 female equivalent of attractant. Numerous thin-walled sensoria are present on the eight distal segments of the male antennae and apparently function as chemoreceptors. Response of males to the attractant was not affected by bilateral amputation of the five distal segments, decreased progressively with the amputation of segments 6 and 7, and was eliminated upon removal of segment 8. Males of L. californicus responded only to extracts of females of that species whereas males of Limonius canus (LeConte) responded to extracts of females of both species.

A Sex Pheromone in the Pacific Coast Wireworm12

A sex pheromone was extracted with ether and with methylene chloride from virgin females of the Pacific Coast wireworm. Limonius canus LeConte. In laboratory bioassays, male beetles became sexually excited when they were offered glass rods that had been dipped into these crude extracts Containing as little as 0.005 female equivalents per ml of solvent. In field tests, the extracted pheromone attracted male beetles even when low concentrations were used in unfavorable weather or in the presence of natural pheromone from wild virgin females. Chemical tests indicate that the pheromone is a carboxylic acid.

Control of Wireworms on Potatoes in Eastern Washington by Soil Fumigants and Organophosphorous Insecticides123

Soil fumigation with Telone® (mixed dichloropropenes), DD® Mixture (dichloropropanc-dichloropropene mixture), and ethylene dibromide, applied at 20 gal, 25 gal, and 36 lb/acre, respectively, and broadcast applications of granulated diazinon, parathion, and phorate, applied at 2, 4, and 3 lb/acre respectively, gave economic control of the Pacific Coast wireworm ( Limonius canus LeConte) on potatoes in sandy loam soil. Cullage was reduced 93.6-100%. Granulated disulfoton, broadcast at 3 lb/acre, gave significantly less control than other broadcast treatments. Post-planting sidedressings of granulated parathion, phorate, Stauffer N-2790 ( O -ethyl S-phenyl ethylphosphonodithioate), and Bayer 25141 [ O-O -diethyl O-p -(methylsulrfinyl)phenyl phosphorothioate), applied at 3 lb/acre, reduced cullage 74.4-85.2%. Granulated disulfoton and Bayer 37289 ( O -ethyl 0-2,4,5-trichlorophenyl ethylphosphonothioate) at 3 lb and naphthalene crystals at 450 lb/acre were significantly inferior to the other sidedress treatments. Phorate and disulfoton granules gave as good control when metered onto the soil surface in bands 6 in, wide in the furrow left by the press-wheel potato planter as when side dressed in the soil at the same rate. Of all diazinon, disulfoton, parathion, and phorate treatments, only phorate applied in the planter press-wheel furrow left a detectable residue above the tolerance in tubers collected 3 weeks before harvest.

Larval Determination of Six Economic Species of Limonius (Coleoptera: Elateridae)1

Wireworms are primary insect pests of crops in the irrigated lands of the Pacific Northwest, and more locally throughout the United States. Those of importance to agriculture throughout this country represent perhaps three-score species, distributed among several genera. In the Pacific Northwest the most important species belong to the genus Limonius, and the major part of the control work has been done on these species. The Pacific Coast wireworm (Limonius canus Lee.) and the sugar-beet wireworm (L. californicus Mann.) are generally distributed throughout both the irrigated and the naturally moist areas of the semiarid portions of the United States west of the Rocky Mountains. The western field wireworm (L. infuscatus Mots.) and the Columbia Basin wireworm (L. subauratus Lee.) are not so generally distributed, but are of economic importance in limited areas, and are frequently associated with L. canus and L. californicus. Observations, field studies, and laboratory experiments show that the larvae and the adults of these species show specific differences in their response to field conditions and treatments.