Susceptibility of immature Ixodes scapularis (Acari: Ixodidae) to desiccants and an insecticidal soap

Efficacy of commercially available formulations of desiccants (Drione, Dri-dic, diatomaceous earth) and insecticidal soap (Safer's) comprised of active ingredients were evaluated against Ixodes scapularis Say immatures in petri dish and grass turf bioassays. In petri dish bioassays at label rate, all products, except diatomaceous earth, provided a high degree of control by 24 and 48 h (71–100% mortality). Mortality of larvae exceeded 94% by 4 h after treatment with Drione (10× label rate held at 85% RH), Dri-die (label rate held at both 85% and 98% RH) and Safer's insecticidal soap (10× label rate held at 98% RH). Nymphal mortality was highest by 4 h after treatment with Safer's insecticidal soap (up to 96%). Larvae were more susceptible than nymphs to desiccants, however, nymphs were more susceptible than larvae to Safer's insecticidal soap. Immature ticks treated with Safer's insecticidal soap exhibited sublethal effects with significantly decreased attachment to hosts and no engorgement. In grass turf bioassays, mortality of nymphs was equivalent (85–95%) between treatments of chlorpyrifos (0.6 kg [AI]/ha, Safer's insecticidal soap, and Drione. In the same bioassays, nymphal mortality was moderate after treatment with Dri-die (23–29%) and low following application with diatomaceous earth (16%) and for untreated controls (6%).     

Response of nymphal Ixodes scapularis, the primary tick vector of Lyme disease spirochetes in North America, to barriers derived from wood products or related home and garden items.

Forest products were tested to see if they functioned as a barrier to nymphal Ixodes scapularis. These products could potentially be used to define a border between high density and low density tick zones on residential properties in Lyme disease endemic regions of North America. Common home and garden items were also tested. Three wood products effectively acted as barriers to nymphal I. scapularis: Alaska Yellow Cedar sawdust, Alaska Yellow Cedar woodchips, and cellulose. These three products were then weathered to determine how long they remained active. Cellulose and Alaska Yellow Cedar woodchips lost their activity almost immediately (within three days); in contrast, Alaska Yellow Cedar sawdust impeded crossing by nymphal ticks for up to one month. Creating barriers at the woods-lawn interface may someday play a role in integrated campaigns to prevent Lyme disease but will not serve as a stand-alone measure to block transmission of Lyme disease spirochetes.     

Cutting edge: Immunity against a "silent" salivary antigen of the Lyme vector Ixodes scapularis impairs its ability to feed

Ixodes scapularis ticks transmit the Lyme disease agent in the United States. Although strong antitick immunity mediates tick rejection by certain vertebrates, only a few Ags have been molecularly characterized. We show that guinea pig vaccination against a secreted tick salivary immunomodulator, sialostatin L2, can lead to decreased feeding ability of I. scapularis nymphs. Increased rejection rate, prolonged feeding time, and apparent signs of inflammation were observed for nymphs attached to vaccinated animals, indicating a protective host immune response. Interestingly, sialostatin L2 humoral recognition does not take place upon repeated tick exposure in control animals, but only in the vaccinated animals that neutralize sialostatin L2 action. Therefore, we demonstrate an essential sialostatin L2 role upon nymphal infestation that can be blocked by vertebrate immunity and propose the discovery of similarly "silent" Ags toward the development of a multicomponent vaccine that will protect against tick bites and the pathogens they transmit.     

The role of direct chilling injury and inoculative freezing in cold tolerance of Amblyomma americanum, Dermacentor variabilis and Ixodes scapularis

Abstract. Supercooling points and chill tolerance were compared among nymphs and adults of the ixodid ticks Dermacentor variabilis, Amblyomma americanum and Ixodes scapularis (Acari: Ixodidae).Supercooling points in the range of <-22 to -18°C were observed for nymphs, and -22 to -8°C for adults.The lower lethal temperatures observed under dry conditions, -14 to -10°C, were warmer than the supercooling points, but still much colder than -4.8°C, the lowest temperature recorded from a likely tick habitat in southwestern Ohio.Based on our experiments, spontaneous freezing and direct chilling injury are not significant mortality factors in these species in the field.Mortality was observed between -5 and -3°C for A.americanum and D.variabilis nymphs chilled for 2 h while in direct contact with ice.This mortality is probably due to inoculative freezing.Given the requirement for a rather humid microhabitat for off-host survival, these findings suggest that inoculative freezing is an important cause of overwintering mortality in these medically important species.     

Blood feeding of Ornithodoros turicata larvae using an artificial membrane system

An artificial membrane system was adapted to feed Ornithodoros turicata (Ixodida: Argasidae) larvae from a laboratory colony using defibrinated swine blood. Aspects related to larval feeding and moulting to the first nymphal instar were evaluated. A total of 55.6% of all larvae exposed to the artificial membrane in two experimental groups fed to repletion and 98.0% of all fed larvae moulted. Mortality rates of first instar nymphs differed significantly depending on the sorting tools used to handle engorged larvae (χ² = 35.578, P < 0.0001): engorged larvae handled with featherweight forceps showed significantly higher mortality (odds ratio = 4.441) than those handled with a camel‐hair brush. Differences in the physical properties of the forceps and camel‐hair brush may affect the viability of fragile soft tick larvae even when care and the same technique are used to sort them during experimental manipulations. The current results represent those of the first study to quantify successful feeding to repletion, moulting and post‐moulting mortality rates in O. turicata larvae using an artificial membrane feeding system. Applications of the artificial membrane feeding system to fill gaps in current knowledge of soft tick biology and the study of soft tick–pathogen interactions are discussed.     

Effectiveness of Metarhizium anisopliae (Deuteromycetes) against Ixodes scapularis (Acari: Ixodidae) engorging on Peromnyscus leucopus.

With the incidence of Lyme disease increasing throughout the United States, reducing risk of exposure to the disease is of the utmost concern. In the northeastern U.S., the blacklegged tick, Ixodes scapularis, is the primary vector and the white-footed mouse, (Peromyscus leucopus), the primary reservoir for Borrelia burgdorteri, the bacterium causing Lyme disease. Targeting I. scapularis engorging on white-footed mice with an effective biological control agent, such as the fungus Metarhizium anisopliae, could be an effective and relatively safe control technique. In 2002-2003, we performed laboratory and field experiments to determine whether M anisopliae-treated nesting material could effectively control larval I. scapularis ticks engorging on white-footed mice, and therefore reduce the number of infected nymphal I. scapularis questing the following summer. Our laboratory experiment demonstrated a strong negative effect of M. anisopliae-treated nesting material on survival of I. scapularis larvae feeding on P. leucopus, with 75% versus 35% larval mortality in treatment versus control nests. Our field trials caused only modest, localized reductions in nymphal abundance and had no effect on the proportion of nymphal I. scapularis infected with B. burgdorferi. Field results probably could be improved by increasing the density of nestboxes to allow fungal delivery to a higher proportion of the mouse population and by deploying nestboxes in an area with lower mammalian diversity, such as a suburban landscape.     

Infection of Ixodes scapularis ticks with Rickettsia monacensis expressing green fluorescent protein: a model system

Ticks (Acari: Ixodidae) are ubiquitous hosts of rickettsiae (Rickettsiaceae: Rickettsia), obligate intracellular bacteria that occur as a continuum from nonpathogenic arthropod endosymbionts to virulent pathogens of both arthropod vectors and vertebrates. Visualization of rickettsiae in hosts has traditionally been limited to techniques utilizing fixed tissues. We report epifluorescence microscopy observations of unfixed tick tissues infected with a spotted fever group endosymbiont, Rickettsia monacensis, transformed to express green fluorescent protein (GFP). Fluorescent rickettsiae were readily visualized in tick tissues. In adult female, but not male, Ixodes scapularis infected by capillary feeding, R. monacensis disseminated from the gut and infected the salivary glands that are crucial to the role of ticks as vectors. The rickettsiae infected the respiratory tracheal system, a potential dissemination pathway and possible infection reservoir during tick molting. R. monacensis disseminated from the gut of capillary fed I. scapularis nymphs and was transstadially transmitted to adults. Larvae, infected by immersion, transstadially transmitted the rickettsiae to nymphs. Infected female I. scapularis did not transovarially transmit R. monacensis to progeny and the rickettsiae were not horizontally transmitted to a rabbit or hamsters. Survival of infected nymphal and adult I. scapularis did not differ from that of uninfected control ticks. R. monacensis did not disseminate from the gut of capillary fed adult female Amblyomma americanum (L.), or adult Dermacentor variabilis (Say) ticks of either sex. Infection of I. scapularis with R. monacensis expressing GFP provides a model system allowing visualization and study of live rickettsiae in unfixed tissues of an arthropod host.     

Essential oils of Cupressus funebris, Juniperus communis, and J. chinensis (Cupressaceae) as repellents against ticks (Acari: Ixodidae) and mosquitoes (Diptera: Culicidae) and as toxicants against mosquitoes

Juniperus communis leaf oil, J. chinensis wood oil, and Cupressus funebris wood oil (Cupressaceae) from China were analyzed by gas chromatography and gas chromatography-mass spectrometry. We identified 104 compounds, representing 66.8-95.5% of the oils. The major components were: α-pinene (27.0%), α-terpinene (14.0%), and linalool (10.9%) for J. communis; cuparene (11.3%) and δ-cadinene (7.8%) for J. chinensis; and α-cedrene (16.9%), cedrol (7.6%), and β-cedrene (5.7%) for C. funebris. The essential oils of C. funebris, J. chinensis, and J. communis were evaluated for repellency against adult yellow fever mosquitoes, Aedes aegypti (L.), host-seeking nymphs of the lone star tick, Amblyomma americanum (L.), and the blacklegged tick, Ixodes scapularis Say, and for toxicity against Ae. aegypti larvae and adults, all in laboratory bioassays. All the oils were repellent to both species of ticks. The EC(95) values of C. funebris, J. communis, and J. chinensis against A. americanum were 0.426, 0.508, and 0.917 mg oil/cm(2) filter paper, respectively, compared to 0.683 mg deet/cm(2) filter paper. All I. scapularis nymphs were repelled by 0.103 mg oil/cm(2) filter paper of C. funebris oil. At 4 h after application, 0.827 mg oil/cm(2) filter paper, C. funebris and J. chinensis oils repelled ≥80% of A. americanum nymphs. The oils of C. funebris and J. chinensis did not prevent female Ae. aegypti from biting at the highest dosage tested (1.500 mg/cm(2) ). However, the oil of J. communis had a Minimum Effective Dosage (estimate of ED(99) ) for repellency of 0.029 ± 0.018 mg/cm(2) ; this oil was nearly as potent as deet. The oil of J. chinensis showed a mild ability to kill Ae. aegypti larvae, at 80 and 100% at 125 and 250 ppm, respectively.     

Abiotic and biotic determinants of tick burdens in the eastern rock sengi (Elephantulus myurus)

Ticks are important vectors of pathogens of medical and veterinary importance worldwide. In spite of their economic importance, our current knowledge about the factors affecting tick prevalence and abundance in tropical and subtropical regions is rather limited. Both abiotic (e.g. temperature) as well as biotic variables (e.g. host sex) have been identified as key determinants of distributions. Eastern rock sengis or elephant shrews (Elephantulus myurus, Macroscelidea: Cacroscelididae, Thomas & Schwann) are widely distributed throughout Africa and can harbour a large number of tick species and substantial tick burdens. In the present study, we evaluated the contribution of climate and host factors on tick burdens of sengis. Throughout the year sengis carried high abundances of immature stages of a single tick species, Rhipicephalus sp. near warburtoni. There was no evidence that host parameters affected tick burdens. However, larval abundance decreased with increasing ambient temperatures and both larvae and nymphs were negatively affected by rainfall 2 months before the sampling month. In addition, nymphal burdens decreased with increasing minimum temperatures. Our results suggest that climate factors are the largest constraint for the immature stages of R. sp. near warburtoni and that eastern rock sengis could play a crucial role in the dynamics of tick-borne diseases as a result of the large tick burdens they can sustain.     

Nosema parkeri sp. n., a Microsporidan from the Argasid Tick, Ornithodoros parkeri Cooley

SYNOPSIS. Nosema parkeri sp. n. is described from nymphs and adults of the argasid tick, Ornithodoros parkeri Cooley, from a laboratory colony. Schizogonic and sporogonic stages are described from various tick tissues. Spores are binucleate, measuring 3.2 (3–4) × 1.9 (1.8–2.5) μm. Transmission is transovarial and transstadial. The parasite does not appear to affect adversely the development or reproduction of the tick. Dermacentor andersoni Stiles was experimentally infected. Attempts to infect Swiss mice by tick feeding or by injection of infected tick suspensions were unsuccessful. The microsporidan differs in structure from Encephalitozoon ixodis Weiser) and Nosema slovaca Weiser & Reháček, the only other microsporidans known from ticks.     

Repellency of deet and SS220 applied to skin involves olfactory sensing by two species of ticks

Responses of host-seeking nymphs of the blacklegged tick, Ixodes scapularis Say and lone star tick, Amblyomma americanum (Linnaeus) (Acari: Ixodidae) to the repellents N,N-diethyl-3-methylbenzamide (deet) and (1S, 2'S)-2-methylpiperidinyl-3-cyclohexene-1-carboxamide (SS220) were studied using fingertip laboratory bioassays. Ethanol solutions of both compounds applied to the skin strongly repelled both species of ticks at 0.8 and 1.6 micromole of compound/cm2 skin. The ticks were also repelled when two layers of organdie cloth covered the portion of a finger treated with either deet or SS220. Gas chromatographic analyses of the outer layer of cloth that had covered skin treated with 1.6 micromole compound/cm2 skin revealed only 0.1 nmole SS220/cm2 cloth and 2.8 nmole deet/cm2 cloth. However, in bioassays in which a single layer of cloth was treated with a dose of deet or SS220 equivalent to the amount found in the outer layer of cloth, ticks were not repelled. Results unequivocally demonstrated that these ticks responded to the repellents in the vapour phase when repellent treated skin was covered with cloth to obviate tactile contact with them, and made it clear that the ticks detect the repellents by olfactory sensing. Heretofore, the mode of action of deet and SS220 was unclear.     

Kinetics of ingested host immunoglobulin G in hemolymph and whole body homogenates during nymphal development of Dermacentor variabilis and Ixodes scapularis ticks (Acari: Ixodidae)

Patterns in the utilization of host immunoglobulin G (IgG) during nymphal development differed between Dermacentor varibilis (Say) and Ixodes scapularis Say ticks. In unfed nymphs of D. variabilis, host IgG was readily detectable in both hemolymph and whole body homogenates. In unfed nymphs of I. scapularis, host IgG was absent in hemolymph and at very low concentrations in whole body homogenates. Host IgG in unfed nymphs was undoubtedly the remnants of IgG acquired during the larval bloodmeal that persisted through metamorphosis to the nymphal stage. In both tick species, host IgG crossed the midgut into the hemocoel during the latter phases of engorgement. Concentrations of host IgG in I. scapularis declined considerably after replete nymphs molted to the adult stage. In contrast, concentrations of host IgG in D. variabilis remained elevated throughout metamorphosis to the adult stage. When larval D. variabilis were fed on a rat, then 2 months later as nymphs on a rabbit, the rat IgG (“old IgG”) present in unfed nymphs was totally replaced by rabbit IgG (“new IgG”) within 2 d of nymphs attaching to the rabbit. Presumably, the old IgG acquired from a previous bloodmeal was secreted via saliva into the new host. This revised version was published online in July 2006 with corrections to the Cover Date.     

Systemic fungicides reduce the abundance of yeast-like symbiotes and the performance of the planthopper Delphacodes kuscheli (Hemiptera: Delphacidae)

Delphacodes kuscheli is the main vector of Mal de Río Cuarto, the most important viral disease of maize in Argentina. This planthopper harbours obligate fungal mutualists, known as yeast-like symbiotes (YLS), which play a key role in the host life cycle. Here, we evaluated the efficacy of six systemic fungicides, prothioconazole (P), prothioconazole & trifloxystrobin (PT), pyraclostrobin & epoxiconazole (PE), pyraclostrobin, epoxiconazole & fluxapyroxad (PEF), picoxystrobin & ciproconazole (PC), and tebuconazole (T) on the reduction of the abundance of YLS in nymphs and newly emerged adults, and the impact of such reduction on the vector performance. All fungicides, except PE, reduced the number of YLS in nymphs treated from 3rd instar five days after starting treatments. When 3rd instar nymphs were allowed to reach adulthood, the fungicides P, PT and PC caused the highest nymphal mortality, significantly reduced the number of YLS in newly emerged adults, lengthened development time and negatively affected morphometric variables of females. There was also a trend towards a higher occurrence of brachypters. In females, the fungicides P, PT and PC caused a greater reduction of YLS when nymphs were treated to these fungicides from 3rd instar compared with nymphs treated from 4th instar. In males, the YLS number was significantly less when nymphs were fed on plants treated with P, PT, PC, and T in 3rd instar. This showed that fungicide treatments caused a greater reduction of YLS when they were applied in early stages of development. Our results provide an effective method to reduce the abundance of YLS in D. kuscheli, contributing to understand the ecological role that these symbionts could be playing in the success of this maize planthopper pest.     

Toxicity of insecticidal soaps to the Asian citrus psyllid and two of its natural enemies

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is an important pest of citrus because it transmits plant pathogens responsible for a serious disease of citrus known as huanglongbing. Conventional insecticides are frequently used to manage ACP. Insecticidal soaps (hereafter ‘soaps’) are an insect control option labelled for commercial use as well as for use by homeowners and organic growers. Soaps have been shown to be toxic to some insect pests and therefore might be an alternative to conventional pesticides for control of ACP, but the efficacy of soaps against ACP was largely unknown. Our objective was to test whether different concentrations of two insecticidal soaps, M‐Pede and Safer Insecticidal Soap Concentrate, caused mortality of ACP adults, nymphs and eggs. In addition, we tested whether these soaps were toxic to two natural enemies of ACP, adults of the lady beetle Cycloneda sanguinea (L.) (Coleoptera: Coccinellidae) and the parasitoid Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae). Direct sprays of M‐Pede or Safer Insecticidal Soap were acutely toxic to ACP adults (regardless of gender) and nymphs when applied in solutions of 0.8–2% in water. Insecticidal soaps were non‐toxic to eggs at rates of up to 2%. Residues of soap were less toxic to adult ACP than direct sprays, even when applied at concentrations of up to 4%. M‐Pede or Safer soap at high concentrations (for example, 2% v/v in water) may be an effective alternative to conventional pesticides to manage adult and nymphal ACP, although multiple applications may be needed if a target population includes eggs. A 2% concentration of either soap applied as a direct spray was non‐toxic to adult C. sanguinea but acutely toxic to adult T. radiata. Soaps therefore may be compatible with biological control of ACP by adult coccinellids but not the parasitoid T. radiata.     

Efficacy of acaricidal tags and pour-on as prophylaxis against ticks and louping-ill in red grouse

Abstract This paper examines the efficacy of 10% lambdacyhalothrin-impregnated plastic tags and a deltamethrin pour-on preparation in protecting red grouse chicks from parasitism by ticks and subsequent infection with the louping-ill virus. In 1995, ten red grouse hens ( Lagopus lagopus scoticus ) in a free-living population in north-east Scotland were fitted with lambdacyhalothrin-impregnated plastic tags, glued to radio transmitters. Chicks of more than 10 days of age from a further ten untreated radio-collared hens were caught and fitted with individual tags to the plagium. Both treatments significantly reduced tick burdens in the short term. The number of larvae and nymphs on chicks up to 45 days was less under both treatments than on control chicks and tagged chicks had fewer nymphs than chicks from treated hens. Nevertheless, treatments did not reduce viral infection rates nor increase survival to 10 weeks, possibly explained by incomplete treatment of tagged broods and/or direct or indirect mortality due to tags. In 1996 chicks in ten broods from hens with radio transmitters were individually treated at 14 days of age at a rate of lmg/kg of chick with a deltamethrin pour-on preparation. This preparation significantly reduced the number of larvae and nymphs on grouse chicks 7–10 days after application below the number on untreated controls. At 20 days from application, however, only larval numbers were lower on treated chicks. Nevertheless louping-ill virus infection prevalences were significantly reduced at 35 days of age and survival of chicks to 10 weeks increased.     

Evaluation of 4-poster acaricide applicators to manage tick populations associated with disease risk in a Tennessee retirement community

In 1993, four residents of a retirement community in middle Tennessee were hospitalized with symptoms of ehrlichiosis causing community managers to implement mitigation methods to reduce tick numbers. For the past four years, managers have utilized 4-poster acaricide applicators that aim to reduce disease risk to residents by killing ticks that feed on deer. To determine the efficacy of this technique, we assessed Amblyomma americanum abundance in the vicinity of the devices by dragging 400 m vegetation transects once per month while ticks were active. In 2009, adult tick activity peaked in May, nymphal tick activity peaked in June, and larval activity peaked in September. Close to 4-poster devices, larval, nymphal, and adult tick abundances were reduced by 91%, 68%, and 49%, respectively (larval and nymphal p<0.001, adult p=0.005), relative to nearby untreated areas. No significant reduction in nymphal or adult A. americanum ticks was evident >300 m from 4-poster devices, however a ～90% reduction in larvae was observed to our sampling limit (400 m). At the low density at which these devices are currently being used (average distance between devices = 6.6 km), we conclude that they will have little large-scale effect on the health risk posed by ticks in this community.     

Blood deprivation and heat stress increase mortality in bed bugs (Cimex lectularius) exposed to insect pathogenic fungi or desiccant dust

Bed bugs (Cimex lectularius L.) have returned as a nuisance pest in the last 20 years. Different bed bug control measures in combination have not been thoroughly studied, although induction of multiple stressors may improve extermination. The effects of heat stress only, heat stress followed by exposure to insect pathogenic fungi, and heat stress followed by exposure to desiccant dust on starved and blood‐fed bed bugs were investigated. Five days at 22 °C (control), 32 °C, 34 °C, or 36 °C (heat stress) did not cause mortality in adults. However, their starved first instar nymphs produced after heat stress suffered mortalities of 33%, 56% and 100%, respectively. Exposure to insect pathogenic fungi after heat stress increased the mortality of adults and their progeny compared to exposure to fungi without heat stress. The beneficial effects of heat stress were not observed in blood‐fed bed bugs. Desiccant dust killed all nymphs within 2 days and all adults within 3 days regardless of previous heat stress, but survival time was prolonged by access to blood. This study highlights the advantage of combining different methods in pest management, and points to heat stress combined with blood deprivation as possible management elements to increase the control success.     

Susceptibility of Ixodes scapularis (Acari: Ixodidae) to Metarhizium brunneum F52 (Hypocreales: Clavicipitaceae) using three exposure assays in the laboratory

An emulsifiable concentrate (EC) and granular (G) formulation of the entomopathogenic fungus, Metarhizium brunneum strain F52 (formerly Metarhizium anisopliae strain F52) were tested against unfed adults and nymphs of Ixodes scapularis Say in the laboratory. Three exposure methods; dip, surface contact, and direct spray application, and three exposure time intervals (3, 30, and 300 min) were used to evaluate the EC formulation. Application rates ranged from 2.6 x 10(2) to 2.6 x 10(8) conidia/cm2. The surface treatment was used for granular formulation with concentrations ranging from 2.3 x 10(5) to 2.3 x 10(7) conidia/cm2 for same three exposure times. Both the EC and G formulations of this fungus were highly pathogenic against I. scapularis adults and nymphs. Logistic regression analysis found formulation, spore concentration, time of exposure, and observation period were significant or highly significant factors influencing tick mortality. For adult I. scapularis, the spray application with the EC formulation of M. brunneum F52 resulted in a lower LC50 (5.9 x 10(4) conidia/cm2) at 30 min than surface exposure to the EC (LC50 = 1.3 x 10(6) conidia/cm2) or G formulation (LC50 = 8.1 x 10(5) conidia/cm2). At higher concentrations, fungal activity was evident in adult I. scapularis held at 5 degrees C suggesting the fungus may provide control in the cooler fall season. While the observed pathogenicity of a fungus against ticks can be dependent upon the bioassay assessment, we found nymphs and adults of I. scapularis to be highly susceptible to M. brunneum F52, regardless of the exposure method used.     

Experimental use of two standard tick collection methods to evaluate the relative effectiveness of several plant-derived and synthetic repellents against Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae)

We used two standard tick collection methods to test the relative effectiveness of two natural product compounds (nootkatone and carvacrol, classified as an eremophilene sesquiterpene and a monoterpene, respectively, that are derived from botanical sources) with commercially-available plant-derived (EcoSMART Organic Insect Repellent, comprised of plant essential oils) and permethrin-based (Repel Permanone) repellents against Ixodes scapularis Say and Amblyomma americanum (L.). Cloth drags were equally effective in sampling both species of host-seeking nymphs, whereas CO, traps attracted primarily A. americanum. All four repellents performed well on drags, with nootkatone and Permanone Repel (100% repelled through 14 d) slightly more effective than carvacrol and EcoSMART (90.7% and 97.7% repelled at 14 d, respectively) at repelling I. scapularis nymphs. Although the same trend in percent repellency was noted in the CO2 trap trial against both A. americanum nymphs and adults, EcoSMART outperformed Permanone in repelling A. Americanum nymphs after 14 d in the drag trial. Generally, the effectiveness of all repellents tested declined over time. The use of tick drags and CO2 traps was rapid, inexpensive, and easy to use in determining the relative effectiveness of repellents in the field.     

Suppression of host-seeking Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) nymphs after dual applications of plant-derived acaricides in New Jersey

We evaluated the ability of dual applications of natural, plant-derived acaricides to suppress nymphal Ixodes scapularis Say and Amblyomma americanum (L.) (Acari: Ixodidae) in a Lyme disease endemic area of New Jersey. An aqueous formulation of 2% nootkatone provided >90% control of I. scapularis through 7 d. Control declined to 80.9% at 14 d, and a second application was made that provided >95% control through the remaining 4 wk of the nymphal season. Nootkatone provided >90% control of A. americanum through 35 d postapplication. Applications of 2% carvacrol and EcoTrol T&O resulted in rapid knockdown of both tick species, but control declined significantly to 76.7 and 73.7%, respectively, after 14 d when a second application was made that extended control of both tick species to between 86.2 and 94.8% at 21 d. Subsequently, control declined steadily in all plots by 42 d postapplication except for I. scapularis in carvacrol-treated plots, where levels of control >90% were observed through 35 d. Of the three compounds tested, 2% nootkatone provided the most consistent results, with 96.5 and 91.9% control of I. scapularis and A. americanum through 42 and 35 d, respectively. The ability of plant-derived natural products to quickly suppress and maintain significant control of populations of these medically important ticks may represent a future alternative to the use of conventional synthetic acaricides. In addition, the demonstrated efficacy of properly-timed backpack sprayer application may enable homeowner access to these minimal-risk acaricides.