Efficacy of novaluron as a feed-through for control of immature horn flies, house flies, and stable flies (Diptera: Muscidae) developing in cow manure.

Two rates (0.4 mg/kg body weight/d and 0.6 mg/kg body weight/d) of a daily feed-through formulation of novaluron (Novaluron 0.67% active ingredient Cattle Mix), a newer benzoylphenyl urea insecticide, were evaluated for efficacy in controlling the larval stage of horn flies, Haematobia irritans (L.), house flies, Musca domestica L., and stable flies, Stomoxys calcitrans (L.), developing in cow manure. Both rates of feed-through novaluron, delivered consecutively for 10 d, reduced adult emergence of all three species when compared with the untreated control. The presence of deformed puparia indicated that novaluron had an insect growth regulator effect on the developing fly larvae. Both of the feed-through rates evaluated resulted in 100% reduction of adult stable fly emergence after the second day of feed-through treatment. The level of control efficacy observed against these three fly species make this feed-through formulation a candidate for use in an integrated livestock pest management program, particularly in confined cattle production situations where a feed-through product could be easily administered.

Effects of a fipronil spot treatment on field colonies of Coptotermes formosanus (Isoptera: Rhinotermitidae).

This field study investigated the colony effect of a fipronil spot treatment applied to active infestations of Formosan subterranean termite, Coptotermes formosanus Shiraki. Spot treatments were applied to a single active independent monitor from each of four colonies in which multiple independent monitors were established. All treated monitors were abandoned, and the contents of the treated monitors were replaced with untreated wood at the approximately 30-d posttreatment inspection. All colonies survived treatment and only one colony exhibited long-term effects, which included significant reductions in termite collections and increased worker size. The affected colony was treated within 1 m of its primary nest. Two colonies exhibited a correlation between monitor termite production and distance from treatment. Distance appears to be a factor limiting fipronil's colony effects. The Formosan subterranean termite may not be a good candidate for the exterior perimeter and localized interior treatment label option because of the large range and size of the colony.

Laboratory evaluation of novaluron as a development site treatment for controlling larval horn flies, house flies, and stable flies (Diptera: Muscidae).

A granular formulation of novaluron (Novaluron 0.2G, 0.2% [AI]), a newer benzoylphenyl urea insecticide, was evaluated for its efficacy in controlling the larval stage of horn flies, Haematobia irritans (L.); house flies, Musca domestica L.; and stable flies, Stomoxys calcitrans (L.), in cow manure. Various rates and insecticide placement locations (top, middle, and bottom of manure) were evaluated in this study and all combinations of these variables reduced adult emergence of all three species when compared with the untreated controls. The presence of deformed pupae indicated that novaluron had an insect growth regulator effect on the developing fly larvae. Top, middle, or bottom application rates of 0.125, 0.195, 0.25, and 0.375 g novaluron onto manure samples, reduced adult horn fly emergence by > 90%. Middle and bottom application rates of 0.195, 0.25, and 0.375 g novaluron reduced adult house fly emergence >93%. All rates and placement combinations resulted in >98% reduction of adult stable fly emergence. The level of control efficacy observed against these three fly species along with the ease of use of a granular formulation, make this product an ideal candidate for use in an integrated livestock pest management program.

Efficacy of amitraz-impregnated collars on white-tailed deer (Artiodactyla: Cervidae) in reducing free-living populations of lone star ticks (Acari: Ixodidae).

Over a 7 yr period, we monitored the effect of a commercially available, amitraz impregnated anti-tick collar in controlling free-living populations of lone star ticks, Amblyomma americanum (L.) when manually fitted around necks of white-tailed deer, Odocoileus virginianus (Zimmermann). Study animals in treatment and control groups were confined in 38.8 ha game-fenced and densely vegetated treatment plots in South Texas. Tick densities during years 1 and 7 served as untreated pre- and posttreatment comparisons and treatments occurred during years 2 through 5. Reductions in tick densities in the treatment plot were compared against tick densities in a control plot having similar vegetation and numbers of untreated deer. During years of treatment, indices of control pressure ranged from 18.2 to 82.6 for nymphs and 16.9-78.7 for adults, and efficacy, expressed as percentage control during the final year of treatment, was 77.2 and 85.0%, respectively, for nymphal and adult ticks. These data show that acaricidal collar treatments provide efficacies very similar to those achieved with the existing ivermectin-medicated bait and '4-Poster' topical treatment technologies to control ticks feeding on wild white-tailed deer.

Distribution of Rhipicephalus (Boophilus) microplus and Rhipicephalus (Boophilus) annulatus (Acari: Ixodidae) infestations detected in the United States along the Texas/Mexico border.

Species identification and global positioning system coordinates of infestations of cattle fever ticks, Rhipicephalus (Boophilus) annulatus (Say) and Rhipicephalus (Boophilus) microplus (Canestrini), were determined for 790 specimens submitted to the National Veterinary Services Laboratory between 1 October 1999 and 30 September 2010. Cattle fever tick specimens obtained by personnel of the United States Department of Agriculture-Animal and Plant Health Inspection Service-Cattle Fever Tick Eradication Program from infested cattle and wildlife along the Texas/ Mexico border were submitted for identification, as required by the program. A geographic information system database was developed that incorporates location, collection, and infestation records. Submitted ticks came from 11 Texas counties and were comprised of 19.5% R. (B.) annulatus and 80.5% R. (B.) microplus. Maps produced from this study locate and define the parapatric boundary between R. (B.) annulatus and R. (B.) microplus.

Evidence for role of white-tailed deer (Artiodactyla: Cervidae) in epizootiology of cattle ticks and southern cattle ticks (Acari: Ixodidae) in reinfestations along the Texas/Mexico border in south Texas: a review and update.

From 1907 when the fever tick eradication campaign began until 1933, the tick eradication methods of dipping cattle in an acaricide or "pasture vacation" were enormously successful in eradicating southern cattle ticks [Rhipicephalus (Boophilus) microplus (Canestrini)], until failures began to occur in some areas of Florida. Regarding the failures in Florida, the consensus was that populations of white-tailed deer [Odocoileus virginianus (Zimmermann)] infested with southern cattle ticks were responsible. After numerous deer in several counties were killed, eradication was achieved in Florida. As in Florida, in Texas increasing numbers of failures of the pasture vacation approach to tick eradication from the 1970s to the present are known to be related to the abundance of white-tailed deer and perhaps other wild ungulate species. A sizable body of evidence confirms the hypothesis that white-tailed deer support the dispersal and maintenance of both cattle ticks [Rhipicephalus (Boophilus) annulatus (Say)] and southern cattle ticks (cattle fever ticks) within the permanent quarantine or buffer zone in South Texas along the Rio Grande, as well as in the so-called free ("cattle fever tick-free") area north and east of the buffer zone and extending to the east coast of the United States. As of August 2009, in addition to the permanent quarantine zone of approximately 2233 km2, three temporary preventative or blanket quarantines were established. Currently, only two methodologies exist to control ticks feeding on white-tailed deer: (1) a systemic treatment method involving dispersal of ivermectin-medicated corn, Zea mays L.; and (2) two topical treatment methods, '4-poster' deer treatment bait stations and '2-poster' deer treatment feeder adapters, both of which passively apply topically active acaricide to deer for the eradication of populations of cattle fever tick associated with white-tailed deer. This study presents and summarizes confirmational support for the role of white-tailed deer derived from historical accounts, circumstantial evidence from review of recent infestations, and cattle fever tick infestations on white-tailed deer that were live-captured and examined specifically for cattle fever ticks.

Juvenile hormone: evidence of its role in the reproduction of ticks.

Ovarian dlevelopmnent, vitellogenesis, andt etnbrvogenesis in recently matedlce fiemnales of tlhe sofi tick Ornithodoros parkeri Coolev were prevented by topical application of the insect antiallatotropin precocene 2. ThCe blockage was relieved by topical application of jtivenile hormonoe. Cancellation of the anti-juvenile hormnone jJects of precocene 2 and the reestablishment of oogenesis (and oviposition in one specimen) bv a naturally occurring insect juvenile hormone argues strongly for a physiological role of juvenile hormone in acarine reproduction.

Effects of photoperiod on reproduction, nymphal developmental timing, and diapause in Amblyomma maculatum (Acari: Ixodidae).

Female engorgement weight, oviposition, and molting times of larvae and nymphs of Amblyomma maculatum Koch (Acari: Ixodidae) were studied at various photoperiods under constant humidity and temperature in the laboratory. Ticks were held at photoperiods of 0:24, 10:14, 12:12, or 14:10 (L:D) h from egg through unfed nymphal stage and then at either the same or a different regime from fed nymphs to adults. No significant effects were observed on oviposition, female engorgement weights, survival, or molting time to unfed nymphs. Nymphal molting times were significantly shorter at the short-day regime (10:14) during the larval stage and 12:12 during the nymphal stage compared with those held at either 14:10 during both life periods or at 0:24 during both life periods. Longer molting times also were observed in ticks held at 12:12 during the larval phase and either 10:14, 12:12, or 0:24 during the nymphal phase compared with 14:10 during both life periods or 0:24 during both life periods. Ticks held at 10:14 during the larval phase and at 0:24 or 10:14 had longer molting times compared with those at 14:10 or 0:24 during both life periods. No differences in survival to either nymphal or adult stages were observed at any regime, and at day 25 no individuals were observed to be in developmental diapause. This study demonstrates that developmental diapause does not seem to be photoperiodically induced in fed nymphal A. maculatum in the laboratory.

Efficacy of eprinomectin and doramectin against Amblyomma americanum (Acari: Ixodidae) on cattle.

Steers were treated with doramectin or eprinomectin by daily oral capsule for 28 consecutive days. The level of doramectin in the serum of steers treated at 200 microg/kg/d reached a maximum of 104.0 +/- 22.1 ppb at day 21 and declined from 93.3 +/- 20.5 ppb on the final day of treatment to below detectable by day 56. Steers treated at 50 microg/kg/d reached a maximum level of doramectin in the serum of 24.7 +/- 1.2 ppb on day 21 and declined from 24.7 +/- 0.6 ppb on the final day of treatment to less than detectable on day 42. Both doramectin dosages provided 100% control of estimated larvae (EL) of Amblyomma americanum (L.) (Acari: Ixodidae) throughout the 28-d treatment period. Daily oral treatment with eprinomectin at a dosage of 200 microg/kg for 28 consecutive days produced a maximum concentration in the serum of 41.6 +/- 11.0 ppb at day 14. On the final day of eprinomectin treatment, the serum concentration was 38.3 +/- 5.9 ppb. Seven days later at day 35, eprinomectin was not detectable in the serum. For steers treated at 50 microg/kg/d for 28 consecutive days, the serum level of eprinomectin reached a maximum of 10.0 +/- 3.0 ppb on day 28 and was undetectable on day 35. Both eprinomectin dosages provided complete control of EL of A. americanum during the 28-d treatment period. Because eprinomectin is efficacious against A. americanum at lower serum levels in cattle and is eliminated from the serum at a more rapid rate than either doramectin or ivermectin, it provides advantages for use in applications such as the medicated bait for control of ticks on white-tailed deer and could have potential for use in the Cattle Fever Tick Eradication Program.

A sustained release gel formulation of doramectin for control of lone star ticks (Acari: Ixodidae) and horn flies (Diptera: Muscidae) on cattle.

A gel formulation formed by incorporating technical doramectin into a 10% hydroxypropyl methylcellulose aqueous solution was used to subcutaneously inject steers at varying dosages. Doramectin serum concentration of steers receiving 600 microg (AI)/kg body weight declined from 21.9 ppb at 0.5 wk to below detectable at 8 wk postinjection. The 1,200 microg (AI)/kg injection resulted in serum concentrations of 29.1 ppb at 0.5 wk and declined to 0.5 ppb at 8 wk postinjection. Both the 600 and 1,200 microg (AI)/kg injections provided 100% inhibition of index of fecundity (IF) in adult lone star ticks, Amblyomma americanum L. (Acari: Ixodidae) through week 8, after which inhibition declined to 79.4 and 45.3%, respectively, during the 12th week posttreatment. For steers treated at 600 microg (AI)/kg, mortality of adult horn flies, Hematobia irritans L. (Diptera: Muscidae), declined from 16.9% during week 2 to 3.1% during week 7 postinjection. The blood from steers treated at 1,200 microg (AI)/kg resulted in a similar decline in mortality of blood fed adult horn flies from 29.4% during week 1 to 4.0% during week 7. The 600 microg (AI)/kg treatment provided complete control of larval horn flies in the manure for 9 wk, whereas the 1,200 microg (AI)/kg injection gave complete control for 14 wk posttreatment. The doramectin gel formulation provided long-lasting delivery of doramectin to cattle and extended control of lone star ticks and larval horn flies. Such a simple and inexpensive formulation could be useful in tick eradication programs by reducing the frequency of gathering cattle.

Reduced interference by gray squirrels with 4-poster deer treatment bait stations by using timed-release bait.

When white-tailed deer, Odocoileus virginianus, feed on corn bait dispensed by 4-poster tick control devices, they rub against paint rollers impregnated with acaricide. Gray squirrels, Sciurus carolinensis, also feed on the corn bait in the feeding troughs of 4-posters, but in doing so, leave abundant corn fragments and meal that impede the flow of uneaten corn into the troughs. Large accumulations of fragments and meal adversely affect the operation of 4-posters and their use by deer. A battery-operated closure mechanism controlled by a photo sensor was developed to block the flow of corn into the troughs during the day when squirrels are active and deer infrequently visit 4-posters. The effectiveness of the diurnal corn restriction (DCR) concept and restriction mechanism was tested in a field trial at a tick-infested site in Maryland. DCR effectively eliminated accumulation of whole corn, partially eaten corn and corn meal in corn troughs associated with squirrel feeding. At the same time, deer usage of 4-posters was not diminished.

Biochemical diagnosis of organophosphate-insensitivity with neural acetylcholinesterase extracted by sonication from the adult tick synganglion.

A sonication method for the homogeneous extraction of acetylcholinesterase (AChE) from the synganglia of adult ticks is described. The method provides for the extraction of sufficient AChE for multiple assays of enzyme activity in the presence of specific organophosphate (OP) inhibitors for the rapid diagnosis of OP-insensitivity and assignment of homozygous susceptible (SS), heterozygous resistant (RS), and homozygous resistant (RR) genotypes to individual ticks. A single synganglion from adult ticks of either gender and various stages of feeding can successfully be used for AChE extraction. The study presents the results of diagnostic screening of four Boophilus microplus strains for OP-insensitivity. The extraction method and these findings should find utility in support of researchers involved in the mitigation of acaricide resistance in tick populations worldwide, and in particular, the Cattle Fever Tick Surveillance and Quarantine Program maintained by USDA-APHIS/Veterinary Services along the south Texas border that prevents reentry of Boophilus spp. into the United States from endemic populations in Mexico.

Synganglial and neurosecretory morphology of the chicken mite Dermanyssus gallinae (DeGeer) (Mesostigmata: Dermanyssidae).

Histological techniques and paraldehyde-fuchsin (PAF) staining were used to study the synganglion and to locate neurosecretory regions and neurosecretion within the synganglion of the chicken mite, Dermanyssus gallinae. The synganglion, which is formed internally by neuropilar ganglia, gives rise to a single esophageal and paired cheliceral, palpal, pedal (I-IV), and opisthosomal nerves. The neuropilar ganglia are interconnected by commissures and connectives within the synganglion. Twelve PAF-positive neurosecretory regions are present in unfed protonymphs, unfed deutonymphs, virgin males and females, and mated males. There are 11 PAF-positive neurosecretory regions in larvae, 24-72 hours post-fed deutonymphs and mated females. Neurosecretory regions in these developmental stadia are described in relation to their positions adjacent to individual neuropilar ganglia.

Selective breeding for photoperiodically induced developmental diapause in laboratory strains of Amblyomma americanum (Acari: Ixodidae).

Offspring of Amblyomma americanum (L.) reared for four generations in a 12:12 (L:D) photoperiod in the laboratory were held in 10:14 (L:D) conditions and bred to select for developmental diapause (DIA) or nondiapause (NON) characteristics for two additional generations. Sequential generations of fed DIA nymphs had mean molting times (days from detachment to ecdysis) that were 8.0% (DIA1) and 35.7% (DIA2) greater than parental ticks, and maximal development time was extended by 20% in DIA2 ticks over that of parentals. Selection in NON strains resulted in a significant decrease of detachment to ecdysis times in NON1 ticks, but the detachment to ecdysis times in NON2 ticks increased and was not different from parental ticks. Breeding for DIA and NON extremes did not affect the ability of either strain to develop rapidly if held in long-light (14:10 [L:D]) conditions. Selection for DIA resulted in extension of the period from detachment of fed nymphs to preapolysial posturing rather than from posturing to ecdysis of adults.

Differential effects of photoperiod on development and reproduction in "montane" and "prairie" strains of the Rocky Mountain wood tick (Acari: Ixodidae).

Progeny of Dermacentor andersoni Stiles adults collected from one "montane" and two "prairie" sites in southern Alberta, Canada, were exposed to combinations of 9:15, 11:13 and 13:11 (L:D) daily photoperiods during various stages of their life cycle. Time required for developmental and reproductive events was recorded. Significant differences in mean molting times of fed larvae were observed, yet the differences were small, and mean times were not attributed to photoperiodic regime. Fed nymphal "prairie" ticks had significantly longer developmental rates under decreasing light regimes than in constant or increasing regimes, while "montane" ticks showed no differential response to any of these regimes. Engorged "montane" females in all regimes weighed significantly more than those in either "prairie" strain, and "prairie" strain females in increasing and constant short-day regimes were significantly heavier than those in decreasing and constant long-day regimes. Photoperiod is unimportant in the regulation of fed-larval development, and the magnitude of female engorgement may be nominally favored by short-day and increasing regimes. The differential phenotypic expression of photoperiodic regulation of fed nymphal development in this tick may have resulted from selective pressures involving differences in host availability and moisture conditions in the two geographic regions.

Synganglial morphology and neurosecretory centers of adult Amblyomma americanum (L.) (Acari: Ixodidae).

Lone star ticks, Amblyomma americanum (L.), were processed by standard histological means for paraffin embedding, sectioning, and staining by the paraldehyde-fuchsin technique. The synganglion is highly condensed around the esophagus and possesses paired optic, cheliceral, palpal, pedal I-IV nerves, and opisthosomal nerves and a single unpaired esophageal nerve. Although optic nerves were observed leading from the eyes to the protocerebrum, distinct optic ganglia were not seen in any of the preparations examined. The paraldehyde-fuchsin technique revealed 14 neurosecretory centers (11 paired, 3 unpaired) within the synganglion, which are described in relation to the underlying neuropilar structure. A previously undescribed internal subesophageal center that consists of a single cell was observed within a cluster of perikarya lying posteriorly adjacent to the esophagus. A three-dimensional reconstruction of the internal neuropilar structure of the synganglion was made, and the included neurosecretory centers were mapped. Comparisons are made to previous work on other ticks, and physiological relationships are considered.

Efficacy of amitraz applied to white-tailed deer by the '4-poster' topical treatment device in controlling free-living lone star ticks (Acari: Ixodidae).

White-tailed deer treated themselves with a commercial pour-on acaricide formulation containing 2% amitraz as they fed from an ARS-patented '4-poster' topical treatment device. Whole kernel corn attracted deer to a single device placed in each of two deer-fenced pastures. In the treatment pasture, the rollers of the treatment device were charged with the acaricide, whereas the rollers of the device in the other pasture remained untreated. Deer were allowed to use the '4-posters' during periods of tick activity beginning in early to midspring and lasting through late summer to early fall for three consecutive years. Pretreatment sampling of adults and nymphs with dry-ice traps and larval masses with flip cloths showed no significant differences in population indices between the two pastures; however, after the third year of treatment, control of nymphal and adult ticks in the treated pasture was 91.9 and 93.7%, respectively, when compared with the untreated pasture. Control of larval masses increased from 68.4% in year 1 to 96.4% in year 2, but declined to 88.0% in year 3, probably because of the presence of feral hogs. This study demonstrated that application of amitraz to white-tailed deer through free-choice interaction with a '4-poster' device significantly reduced the abundance of free-living lone star ticks in a deer-fenced experimental pasture. Moreover, the yearly pattern of incremental increases in control and the final percentage control values for all three parasitic life stages in this topical application study were similar in magnitude to that observed in a previously conducted study in which the systemic acaricide ivermectin was used to reduce populations of free-living ticks by controlling ticks on deer.

Observations of the rhythm of detachment of engorged female Boophilus annulatus (Acari: Ixodidae) from cattle.

A bimodal, diurnal rhythm of detachment was observed for engorged female Boophilus annulatus fed on Hereford heifers confined in individual stalls in an open-sided barn and exposed to ambient climate and light. In 3 experiments during which hosts were fed each morning and evening, a morning period of increased detachment activity occurred during a 6-h period centered around the 2-h collecting interval in which sunrise occurred. A 2nd peak of activity occurred during the 2-h interval that began 6-8 h later. Seventy-four to 84% of the total detachment occurred during these two 6-h intervals and most of the detachment (44-62%) occurred during the afternoon period. These experiments were done in July, September, and January when daylengths were 13 h, 27 min; 12 h, 22 min; and 10 h, 37 min, respectively. In a 4th experiment in which groups of hosts were fed at different times of the day, maximal percentages of 41.5 and 38.3 of the total detachment from morning-fed or both morning and evening-fed heifers, respectively, occurred during the 2-h interval in which the sun rose instead of during the evening. During the evening peak period, the number of engorged females that detached from these 2 groups of heifers was approximately 1/3-1/4 the number that detached during the peak period in the morning. In contrast, 43.6% of the engorged females in the evening-fed group detached during an 8-h morning period of increased detachment activity that began in the interval between 0200 and 0400 hours. About the same percentage of the ticks (38.5) detached during a 6-h period that began at 1400 hours. The less precisely delimited pattern of detachment of engorged females from cattle fed only in the evening, as contrasted with the rhythm observed for ticks that detached from heifers fed in the morning or both morning and evening, indicates that the nutritional or physiological state of the host may influence the rhythm exogenously. Whether the morning or evening peak of detachment activity is dominant is a question that remains unresolved.

Implications of selection and hybridization studies on the mode of inheritance of photoperiodically induced developmental diapause in laboratory strains of the lone star tick (Acari: Ixodidae).

Selection of lone star ticks, Amblyomma americanum (L.), that were reared in the laboratory under short-day photoperiods of 10:14 (L:D) h resulted in third generation (F3) diapause versus F3 nondiapause strain replete nymphs having significantly different mean molting times (days from detachment to ecdysis) of 100.9 versus 54.7 d, respectively; whereas, the F7 unselected laboratory control strain had an even smaller, significantly different mean molting time of 49.5 d. Two hybrid crosses of F2 nondiapause male with F2 diapause female ticks and F2 nondiapause female with F2 diapause male ticks yielded intermediate replete nymphal mean molting times of 62.0 and 68.9 d, respectively. All strains retained the ability to develop rapidly under long-day photoperiodic conditions of 14:10 (L:D) h, although F3 nondiapause strain ticks also exhibited reduced fitness, especially when exposed to the long-day stimuli. Analyses of molting times used as phenotypic values indicate that this diapause trait is incompletely dominant, and these and other observations indicate that inheritance of photoperiodically induced prolonged replete nymphal molting times is polygenic in this species.

The '4-poster' passive topical treatment device to apply acaricide for controlling ticks (Acari: Ixodidae) feeding on white-tailed deer.

A '4-poster' device that attracts white-tailed deer to a bait source, and as they feed, allows a self-application of a pesticide to the head, ears, and neck to control ticks was designed, constructed, and tested. The device consists of a central bin containing bait to attract deer and two feeding and application stations. These stations each have one bait port and two vertical pesticide-impregnated applicator rollers. This design allows unrestricted vertical retraction of the head to minimize injury to the deer or damage to the posts supporting the pesticide application rollers. Observations using deer demonstrated ready acceptance and repeated use by both antlered and antlerless deer. Results of an initial trial indicate that control values for lone star ticks, Amblyomma americanum (L.), exceeded 92-97% on deer that used the device regularly.