S. S. Denning

Mechanical Transmission of Turkey Coronavirus by Domestic Houseflies (Musca domestica Linnaeaus)

SUMMARY. Domestic houseflies (Musca domestica Linnaeaus) were examined for their ability to harbor and transmit turkey coronavirus (TCV). Laboratory-reared flies were experimentally exposed to TCV by allowing flies to imbibe an inoculum comprised of turkey embryo–propagated virus (NC95 strain). TCV was detected in dissected crops from exposed flies for up to 9 hr postexposure; no virus was detected in crops of sham-exposed flies. TCV was not detected in dissected intestinal tissues collected from exposed or sham-exposed flies at any time postexposure. The potential of the housefly to directly transmit TCV to live turkey poults was examined by placing 7-day-old turkey poults in contact with TCV-exposed houseflies 3 hr after flies consumed TCV inoculum. TCV infection was detected in turkeys placed in contact with TCV-exposed flies at densities as low as one fly/bird (TCV antigens detected at 3 days post fly contact in tissues of 3/12 turkeys); however, increased rates of infection were observed with higher fly densities (TCV antigens detected in 9/12 turkeys after contact with 10 flies/bird). This study demonstrates the potential of the housefly to serve as a mechanical vector of TCV.

Lesser Mealworm (Coleoptera: Tenebrionidae) Emergence After Mechanical Incorporation of Poultry Litter into Field Soils

Abstract Lesser mealworm, Alphitobius diaperinus (Panzer), emergence from North Carolina field soils was evaluated in a controlled experiment simulating land application of turkey litter and again in field studies. Adult lesser mealworms were buried in central North Carolina Cecil red clay at depths of 0, 8, 15, 23, and 30 cm and the beetles emerging from the soil counted 1, 3, 7, 10, 13, 17, 21, 24, and 28 d after burial. Beetles emerged from all depths and differences among depths were not significant. Beetles survived at least 28 d buried in the soil at depths ≤30 cm. In seasonal field studies, lesser mealworm emergence from clay soil with poultry litter incorporated by disk, mulch and plow was compared with emergence from plots with no incorporation. Incorporation significantly reduced beetle emergence when poultry litter containing large numbers of beetles was applied to clay field soils during the summer (F = 3.45; df = 3, 143; P = 0.018). Although mechanical incorporation of poultry litter reduced beetle emergence relative to the control, greatest reductions were seen in plowed treatments. Beetle activity was reduced after land application of litter during colder months. Generally, lesser mealworm emergence decreased with time and few beetles emerged from the soil 28 d after litter was applied. Similarly, mechanical incorporation of poultry litter into sandy soils reduced beetle emergence (F = 4.06; df = 3, 143; P < 0.008). In sandy soils typical of eastern North Carolina, disk and plow treatments significantly reduced beetle emergence compared with control.

Experimental evaluation of Musca domestica (Diptera:Muscidae) as a vector of newcastle disease virus

Abstract House flies, Musca domestica L. (Diptera: Muscidae), were examined for their ability to harbor and transmit Newcastle disease virus (family Paramyxoviridae, genus Avulavirus, NDV) by using a mesogenic NDV strain. Laboratory-reared flies were experimentally exposed to NDV (Roakin strain) by allowing flies to imbibe an inoculum consisting of chicken embryo-propagated virus. NDV was detected in dissected crops and intestinal tissues from exposed flies for up to 96 and 24 h postexposure, respectively; no virus was detected in crops and intestines of sham-exposed flies. The potential of the house fly to directly transmit NDV to live chickens was examined by placing 14-d-old chickens in contact with NDV-exposed house flies 2 h after flies consumed NDV inoculum. NDV-exposed house flies contained ≈104 50% infectious doses (ID50) per fly, but no transmission of NDV was observed in chickens placed in contact with exposed flies at densities as high as 25 flies per bird. Subsequent dose–response studies demonstrated that oral exposure, the most likely route for fly-to-chicken transmission, required an NDV (Roakin) dose ≥106 ID50. These results indicate that house flies are capable of harboring NDV (Roakin) but that they are poor vectors of the virus because they carry an insufficient virus titer to cause infection.

Development of a novel walk-through fly trap for the control of horn flies and other pests on pastured dairy cows

A prototype walk-through fly vacuum system, designed to remove horn flies Haematobia irritans (L.) (Diptera: Muscidae) from cattle, was developed and tested for efficacy. The study was conducted during 4 fly seasons over 17 consecutive weeks each year within the months of May through September at 1 dairy research herd in the coastal plain of North Carolina. Additional data on horn flies, as well as face flies (Musca autumnalis) and stable flies (Stomoxys calcitrans), were collected during 1 yr from 7 commercial pasture-based and organic dairy farms in the piedmont region of North Carolina. The number of flies observed on animals in the pasture was compared with the number of flies collected in the trap. Studies were initiated after horn fly densities had met or exceeded a threshold of 200 flies per animal. The vacuum trap removed between 1.3 and 2.5 million flies annually from the research station cattle. Most fly removal occurred during the first few weeks of operation and maintained densities below threshold thereafter. Cattle using the fly trap at the research farm had only about 28% the number of horn flies as untreated cattle, and reductions ranged from 67.5 to 74.5% across the 4-yr study. In addition to large numbers of horn flies, traps placed on commercial dairies during 1 yr collected stable flies, face flies, and house flies, all species with differing behavior and larger in size than horn flies. The estimated cost of running the trap is

Blow flies (Diptera: Calliphoridae) survive burial: Evidence of ascending vertical dispersal

72 per season at commercial rates of

Comparison of Two Fly Traps for the Capture of Horse Flies (Diptera: Tabanidae)

0.12 per hour and an expected 4h of daily operation during the time of milking. Use of a vacuum system as described herein has potential as a cost-effective method in reducing populations of parasitic flies in pasture-based dairy production systems without the use of insecticides.

Field trials of fatty acids and geraniol applied to cattle for suppression of horn flies, Haematobia irritans (Diptera: Muscidae), with observations on fly defensive behaviors

This study was undertaken to determine if immature blow flies could complete development following burial and emerge from the soil as adults. Two species of blow flies, Cochliomyia macellaria and Protophormia terraenovae, were placed at three depths and at three different life stages, in a simulated burial to evaluate the impact of soil on ascending vertical dispersal and fly survival. In soil columns, immature stages of each species were covered with 5, 25 and 50cm of soil. Emerging adult flies of both species reached the surface from all depths at all three immature stages (2nd instar, 3rd instar and pupae). At the 50-cm depth, flies were least successful in reaching the surface when buried as pupae and most successful as late 3rd instar larvae (prepupae). Collectively, more adult flies emerged from the soil if buried as 3rd instars (79.6%) than either 2nd instars or pupae (59.6% and 59.3%, respectively (F(2,159)=14.76, P<0.0001)). Similarly, at shallow burial depths of 5 and 25cm, 75.6% and 70.4% of the adults successfully reached the surface, compared with 52.6% at the 50-cm depth (F(2,159)=15.95, P<0.0001). Second instars demonstrated ascending vertical dispersal behaviours in the soil column by pupating closer to the surface. Nearly half (46.6%) of the C. macellaria 2nd instars buried in 25cm of soil pupated nearer to the surface. Similarly, 45.4% of the P. terraenovae 2nd instars pupated nearer to the surface. When buried at 50cm, approximately 25% of 2nd instars of both species pupated nearer to the surface. When 3rd instars of C. macellaria and P. terraenovae were buried at 120cm, 40% and 4.3% of the adults, respectively, successfully reached the soil surface.

Quantifying pteridines in the heads of blow flies (Diptera: Calliphoridae): Application for forensic entomology

A 2-yr study was conducted to examine differences between two commercially available horse fly traps, the Epps® Biting Fly Trap (Farnum Co., Phoenix, AZ) and the Horse Pal® (Newman Enterprises, Omr...

Effects of Lime Hydrate on the Growth and Development of Darkling Beetle, Alphitobius diaperinus

Adult horn fly populations were tracked on cattle for 2-week periods before, during and after multiple treatments (every 3-4days) with two repellents in a mineral oil carrier. Cattle were sprayed four times in a two-week period either with 2% geraniol (125ml/cow) or a 15% mixture of short chain fatty acids (C8-C9-C10)(250ml/cow), and there were untreated control cattle. Trials were conducted in California and North Carolina for 3 summers. Short-term fly counts (same day) on treated cattle were reduced by 61-99%, depending on material and trial, and the fatty acid mixture provided better control than geraniol. Horn fly counts were suppressed for 1-3 d and rebounded somewhat after both treatments. Consecutive treatments showed evidence of persistent impact in California where herds were more isolated. Rebounds to pre-treatment levels 3-4 d after treatment occurred more often in North Carolina, where other infested cattle were closer to treated herds. By 3-4 d post-treatment, horn flies were reduced by 29-61% in California and 0-83% in North Carolina, relative to pre-treatment. Background behavior frequencies were assessed from hundreds of counts on untreated, infested California cattle, where horn flies were the only abundant biting fly. Behavior averages were 16.5 tail flicks, 7.6 skin twitches, 1.2 head throws, or 0.2 leg stamps per 2min observation period. At horn fly densities from about 200 to more than 1000 flies per animal (moderate to high numbers), fly defensive behaviors on control cattle were poorly related (or unrelated) to fly numbers. Immediately after repellent application, however, flies were almost absent and behavior frequencies dropped distinctly. Cattle fly defensive behaviors therefore seem to be quite sensitive to low (less than 100 flies/animal) horn fly densities, and behaviors would be a poor quantitative tool to track fly stress at moderate densities and above. Both geraniol and the fatty acids show promise for horn fly control, especially in organic agriculture. Treatments at 1-2 d intervals probably would keep infestations below the economic threshold (200 flies/cow).

Managing the Horn Fly (Diptera: Muscidae) Using an Electric Walk-Through Fly Trap

In forensic cases involving entomological evidence, establishing the postcolonization interval (post-CI) is a critical component of the investigation. Traditional methods of estimating the post-CI rely on estimating the age of immature blow flies (Diptera: Calliphoridae) collected from remains. However, in cases of delayed discovery (e.g., when remains are located indoors), these insects may have completed their development and be present in the environment as adults. Adult fly collections are often ignored in cases of advanced decomposition because of a presumed little relevance to the investigation; herein we present information on how these insects can be of value. In this study we applied an age-grading technique to estimate the age of adults of Chrysomya megacephala (Fabricius), Cochliomyia macellaria (Fabricius), and Phormia regina (Meigen), based on the temperature-dependent accumulation of pteridines in the compound eyes, when reared at temperatures ranging from 5 to 35°C. Age could be estimated for all species*sex*rearing temperature combinations (mean r2±SE: 0.90±0.01) for all but P. regina reared at 5.4°C. These models can be used to increase the precision of post-CI estimates for remains found indoors, and the high r2 values of 22 of the 24 regression equations indicates that this is a valid method for estimating the age of adult blow flies at temperatures ≥15°C.