Assessment of infection of Stomoxys calcitrans larvae by entomopathogenic nematodes Heterorhabditis amazonensis NEPT11

This study aimed to evaluate the virulence of Heterorhabditis amazonenses NEPT11 against larvae of Stomoxys calcitrans. Groups of 10 third-instar fly larvae were deposited in Petri dishes, to which were added 50, 100 and 200 EPNs/larva in 4ml of distilled water. The volume of the control group was the same as the treated group, but without EPNs. Larval mortality was observed daily, until larvae died or adults emerged. The Petri dishes were kept on laboratory shelves at 27 ± 1 °C and 70 ± 10% RH. The experiment was replicated six times. A regression analysis revealed quadratic behavior with increasing concentrations, indicating that the concentration of 200 EPNs/larva (48%) was the most efficient among the tested concentrations, while concentrations of 50 and 100 EPNs/larva killed 26.6 and 40% of larvae, respectively. In general, none of the treatments resulted in a mortality rate of more than 50%, but all the treated groups exhibited a higher mortality than that of the control group. It is concluded that the EPN H. amazonensis NEPT11 shows a promising potential to control third-instar larvae of S. calcitrans. However, further studies are needed in different situations to better understand the activity of this organism against the immature stages of the stable fly.

The Defensive Behaviors and Milk Production of Pastured Dairy Cattle in Response to Stable Flies, Horn Flies, and Face Flies

Thirty-four crossbred dairy cows were observed on pasture six times per week from June to August 2014 at the University of Minnesota West Central Research and Outreach Center grazing dairy in Morris, MN, for defensive behaviors in response to three species of muscid flies. Counts of stable flies (Stomoxys calcitrans (L.)), horn flies (Haematobia irritans (L.)), and face flies (Musca autumnalis DeGeer) were recorded before and after pasture observation. Individual cows were monitored for 5 min intervals to observe the frequencies of five different defensive behaviors: front and back leg stomps, head tosses, skin twitches, and tail swishes. Fly numbers averaged 5 stable flies per leg, 37 horn flies per side, and 1 face fly per face during the study. The fly counts and behavior frequencies increased with ambient temperature. The results showed a very strong relationship between the numbers of flies and numbers of defensive behaviors, though correlations between specific flies and behaviors were low. Younger cows had fewer stable flies and horn flies than older cows. The thresholds of flies to lower production for pastured organic dairy cows may be greater than 5 for stable flies, 37 for horn flies, and 1 for face flies.

Evaluation of the effect of Heterorhabditis bacteriophora (HP88) on Stomoxys calcitrans (Linnaeus, 1758) larvae (Diptera: Muscidae) in sugarcane bagasse ash

The purpose of this study was to evaluate the effect of the EPN Heterorhabditis bacteriophora HP88 on Stmoxys. calcitrans larvae in sugarcane bagasse ash. Groups of 10 stable fly larvae were placed in Petri dishes containing filter paper and bagasse ash. Concentrations of 50, 150 and 250 EPNs/larva of S. calcitrans in four milliliters of distilled water were added to each plate. In the control group contained only distilled water, without EPNs. The bioassay had three replications and was maintained at 27 ± 1°C and 70-80% relative humidity. It was observed that mortality rate in all treated groups was significantly higher than in the control group (26,6%). The mortality rate in the presence of 50 EPNs/larva (46,6%) was lower than in 150 EPNs/larva (76,3%), which in turn was lower than 250 EPNs/larva group (93,3%). It was verified by analysis of variance and regression that there was a linear pattern of mortality, that is, the higher the EPNs/larva concentration, the higher the larval mortality. It was concluded that EPN H. bacteriophora HP88 was capable of infecting and causing mortality of stable fly larvae in sugarcane bagasse ash.

Lumpy Skin Disease: A Systematic Review of Mode of Transmission, Risk of Emergence and Risk Entry Pathway

The spread of lumpy skin disease (LSD) to free countries over the last 10 years, particularly countries in Europe, Central and South East Asia, has highlighted the threat of emergence in new areas or re-emergence in countries that achieved eradication. This review aimed to identify studies on LSD epidemiology. A focus was made on hosts, modes of transmission and spread, risks of outbreaks and emergence in new areas. In order to summarize the research progress regarding the epidemiological characteristics of LSD virus over the last 40 years, the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement guidelines were followed, via two databases, i.e., PubMed (biomedical literature) and Scopus (peer-reviewed literature including scientific journals, books, and conference proceedings). A total of 86 scientific articles were considered and classified according to the type of epidemiological study, i.e., experimental versus observational. The main findings and limitations of the retrieved articles were summarized: buffaloes are the main non-cattle hosts, the main transmission mode is mechanical, i.e., via blood-sucking vectors, and stable flies are the most competent vectors. Vectors are mainly responsible for a short-distance spread, while cattle trade spread the virus over long distances. Furthermore, vaccine-recombinant strains have emerged. In conclusion, controlling animal trade and insects in animal transport trucks are the most appropriate measures to limit or prevent LSD (re)emergence.

Why are biting flies attracted to blue objects?

Diurnal biting flies are strongly attracted to blue objects. This behaviour is widely exploited for fly control, but its functional significance is debated. It is hypothesized that blue objects resemble animal hosts; blue surfaces resemble shaded resting places; and blue attraction is a by-product of attraction to polarized light. We computed the fly photoreceptor signals elicited by a large sample of leaf and animal integument reflectance spectra, viewed under open/cloudy illumination and under woodland shade. We then trained artificial neural networks (ANNs) to distinguish animals from leaf backgrounds, and shaded from unshaded surfaces, in order to find the optimal means of doing so based upon the sensory information available to a fly. After training, we challenged ANNs to classify blue objects used in fly control. Trained ANNs could make both discriminations with high accuracy. They discriminated animals from leaves based upon blue-green photoreceptor opponency and commonly misclassified blue objects as animals. Meanwhile, they discriminated shaded from unshaded stimuli using achromatic cues and never misclassified blue objects as shaded. We conclude that blue-green opponency is the most effective means of discriminating animals from leaf backgrounds using a fly's sensory information, and that blue objects resemble animal hosts through such mechanisms.

Evidence of Lumpy Skin Disease Virus Transmission from Subclinically Infected Cattle by Stomoxys calcitrans

Lumpy skin disease virus (LSDV) is a vector-transmitted capripox virus that causes disease in cattle. Stomoxys calcitrans flies are considered to be important vectors as they are able to transmit viruses from cattle with the typical LSDV skin nodules to naive cattle. No conclusive data are, however, available concerning the role of subclinically or preclinically infected cattle in virus transmission. Therefore, an in vivo transmission study with 13 donors, experimentally inoculated with LSDV, and 13 naïve acceptor bulls was performed whereby S. calcitrans flies were fed on either subclinical- or preclinical-infected donor animals. Transmission of LSDV from subclinical donors showing proof of productive virus replication but without formation of skin nodules was demonstrated in two out of five acceptor animals, while no transmission was seen from preclinical donors that developed nodules after Stomoxys calcitrans flies had fed. Interestingly, one of the acceptor animals which became infected developed a subclinical form of the disease. Our results show that subclinical animals can contribute to virus transmission. Therefore, stamping out only clinically diseased LSDV-infected cattle could be insufficient to completely halt the spread and control of the disease.

Pyrethroid Susceptibility in Stomoxys calcitrans and Stomoxys indicus (Diptera: Muscidae) Collected from Cattle Farms in Southern Thailand

The susceptibility to six pyrethroid insecticides (permethrin, deltamethrin, alpha-cypermethrin, cypermethrin, lambda-cyhalothrin, and bifenthrin), each at the recommended concentration, was evaluated for two stable fly species-Stomoxys calcitrans (Linnaeus, 1758) and Stomoxys indicus Picard, 1908 (Diptera: Muscidae)-through tarsal contact using a World Health Organization (WHO) cone bioassay procedure. The field populations of S. calcitrans were collected from the Songkhla and Phattalung provinces, while S. indicus were collected from the Phattalung and Satun provinces in Thailand. The stable flies were exposed to insecticide-treated filter paper for 30 min, and their knockdown counts at 30 min and 60 min and mortality counts at 12 h and 24 h were recorded. The S. calcitrans and S. indicus Songkhla and Phattalung populations were moderately susceptible to pyrethroids, as indicated by the 24 h mortality. Nonetheless, the Satun population of S. indicus was completely susceptible to permethrin, with 100% mortality, and showed the lowest susceptibility to deltamethrin and bifenthrin. The results indicate the generally low susceptibility of stable flies to pyrethroids in the southern provinces of Thailand.

Mechanical transmission of African swine fever virus by Stomoxys calcitrans: Insights from a mechanistic model

African swine fever (ASF) represents a global threat with huge economic consequences for the swine industry. Even though direct contact is likely to be the main transmission route from infected to susceptible hosts, recent epidemiological investigations have raised questions regarding the role of haematophagous arthropods, in particular the stable fly (Stomoxys calcitrans). In this study, we developed a mechanistic vector-borne transmission model for ASF virus (ASFV) within an outdoor domestic pig farm in order to assess the relative contribution of stable flies to the spread of the virus. The model was fitted to the ecology of the vector, its blood-feeding behaviour and pig-to-pig transmission dynamic. Model outputs suggested that in a context of low abundance (<5 flies per pig), stable flies would play a minor role in the spread of ASFV, as they are expected to be responsible for around 10% of transmission events. However, with abundances of 20 and 50 stable flies per pig, the vector-borne transmission would likely be responsible for almost 30% and 50% of transmission events, respectively. In these situations, time to reach a pig mortality of 10% would be reduced by around 26% and 40%, respectively. The sensitivity analysis emphasized that the expected relative contribution of stable flies was strongly dependent on the volume of blood they regurgitated and the infectious dose for pigs. This study identified crucial knowledge gaps that need to be filled in order to assess more precisely the potential contribution of stable flies to the spread of ASFV, including a quantitative description of the populations of haematophagous arthropods that could be found in pig farms, a better understanding of blood-feeding behaviours of stable flies and the quantification of the probability that stable flies partially fed with infectious blood transmit the virus to a susceptible pig during a subsequent blood-feeding attempt.

Attractiveness and Specificity of Different Polyethylene Blue Screens on Stomoxys calcitrans (Diptera: Muscidae)

Stomoxys calcitrans is considered as a major pest of livestock worldwide. Insecticides have been extensively used to control this pest but resistance to these chemical compounds is now reported in many countries. Therefore, a more sustainable and efficient control is needed. Seven different types of blue screens, with reflectances around 460 nm, were tested during summer 2016 in southwestern France to evaluate their attractiveness and their specificity for stable flies. Height of the screen and orientation (east or west) of a blue screen were also considered. High levels of S. calcitrans captures were recorded during this study (from 141 to 7301 individuals per blue screen and per day) whereas the numbers of tabanids and pollinator insects remained extremely low (less than 10 individuals per screen and per day). No significant difference in attractiveness has been shown between the different types of blue screens. The lower half of the blue screens caught significantly more stable flies (70%) than the higher half (30%). The "east" side of the screen attracted 60% of stable flies but this was not significantly different from the west side. These results are highlighting the interest in these blue polyethylene screens for controlling stable flies in cattle farms, in comparison with more expensive blue fabrics.

Adulticidal Activity of Melaleuca alternifolia (Myrtales: Myrtaceae) Essential Oil With High 1,8-Cineole Content Against Stable Flies (Diptera: Muscidae)

The stable fly, Stomoxys calcitrans (Linnaeus 1758), is a hematophagous fly responsible for causing loss of performance in horses, causing losses in cattle productivity, and impacting the animals' health through the spread of pathogenic microorganisms. The objective of this work was to investigate the insecticidal activity of essential oil obtained from Melaleuca alternifolia (Cheel), presenting high 1,8-cineole content, against S. calcitrans adults. Insecticidal activity was determined using surface application methods and exposure to oil impregnated paper. It was observed that treatments at 25 and 50 μg/cm2 (P < 0.05) present fumigant activity through exposure to the impregnated paper, and in the first 15 min of exposure, the mortality rates obtained for these treatments were, respectively (96.6 ± 3.3% and 100%), equivalent to the positive control. Using the superficial application method, the only treatment concentration presenting adulticidal action was 5% (w/v) (P < 0.05). Respective toxicities LC50 (%, w/v) and LC80 for the impregnated paper method were 1.06 ± 0.02 and 1.47 ± 0.17; for the superficial application method, they were 3.82 ± 0.65 and 5.53 ± 0.74. As demonstrated, M. alternifolia essential oil presents adulticidal potential against S. calcitrans.

Species Composition and Abundance of Stomoxys spp. (Diptera: Muscidae) in Peninsular Thailand

Stable fly collections were conducted to study the species composition and daytime activity of Stomoxys spp. (Diptera: Muscidae) in Peninsular Thailand (Songkhla, Trang, Pattalung, Nakon Si Thammarat, and Satun provinces). Vavoua traps were used for fly collections in wet and dry seasons each year. Four Stomoxys species were found, S. calcitrans (L.) (Diptera: Muscidae) being the most common with 2,512 specimens (87.43% of captures), followed by S. indicus (Picard) (Diptera: Muscidae) with 306 specimens (10.65%), S. sitiens (Rondani) (Diptera: Muscidae) with 44 specimens (1.53%), and S. uruma (Shinonaga and Kano) (Diptera: Muscidae) with 11 specimens (0.39%). Subsequently, Songkhla Province was further selected to be a potential collection site to conduct a 1-yr abundance study, due to mixed crop-livestock farming in one place. Stomoxys calcitrans was predominant from 0800 to 1000 h with 4,921 specimens (93.6%) while S. indicus with 317 specimens (6%) and S. sitiens with 19 specimens (0.4%) were numerically dominant from 0600 to 0800 and 1600 to 1800 h. A proportion of male and female of each species was also established. This overall finding could be used as an ideal for nationwide species distribution status for the guidance of appropriate fly control. This information can lighten the way for the future control measures program activity of stable flies in Thailand.

Short communication: Effects of mesh leggings on fly pressure and fly avoidance behaviors of pastured dairy cows

Ectoparasitic stable flies (Stomoxys calcitrans [L.]), horn flies (Haematobia irritans [L.]), and face flies (Musca autumnalis De Geer) negatively affect dry matter intake, milk production, and health of pastured dairy cows. These flies cause fly avoidance behaviors and are a major welfare concern for dairy producers. The objective of this study was to evaluate the effects of mesh Shoofly Leggins (Stone Manufacturing & Supply, Kansas City, MO) on fly avoidance behaviors and numbers of flies attacking pastured dairy cows. In a crossover design, lactating dairy cows (n = 80) were randomly assigned to groups with and without leggings (Shoofly Leggins worn on all legs). All cows were managed in one group. Cows were observed for 2-wk periods, and then treatments were reversed in the next 2-wk interval. Counts of stable flies, horn flies, and face flies on all cows were recorded twice daily (once in morning per cow: 0930 to 1230 h; and once in the afternoon per cow: 1330 to 1630 h), 3 times per wk on Tuesday, Wednesday, and Thursday of each week during the study period. The total number of flies per cow was greater on cows with leggings than cows without leggings. The number of horn flies per cow was greater on cows in with leggings (26.4 flies/side) compared with cows without leggings (24.1 flies/side). Stable fly numbers were similar for cows with and without leggings (12.8 flies/leg). A random subset of 20 focal cows per group was observed during 5-min intervals to record frequencies of 4 behaviors: leg stomps, head tosses, skin twitches, and tail swishes. Counts of head tosses (2.6 vs. 3.1), skin twitches (20.9 vs. 19.6), and tail swishes (21.3 vs. 19.3) were similar for cows without leggings versus cows with leggings, respectively. However, foot stomps were 39% lower for cows with leggings compared with cows without leggings, and leg stomps were 26% higher in the afternoon than in the morning (2.9 vs. 2.4, respectively). A positive correlation was observed between stable and horn flies and all insect avoidance behaviors. Numbers of stable flies were 1.5 times greater in the afternoon than in the morning. The results of this study indicated that flies were associated with cow fly avoidance behaviors regardless of the use of leggings, but leggings effectively reduced foot stomps by 39%, so their use may provide some relief from stable fly injury to pastured dairy cows.

Can Attractive Sticky Traps Be Used to Protect Horses From the Bites of Stomoxys calcitrans (L.) (Diptera: Muscidae)

The stable fly, Stomoxys calcitrans (L.), is a bloodsucking ectoparasite that causes irritation and distress to livestock, wildlife, and humans. Both sexes are vicious blood-feeders that feed on a variety of animals. Optically attractive sticky traps have been used to capture stable flies, and some companies claim that sticky traps can protect animals from the bites of stable flies. To further investigate the protective ability of sticky traps, Home and Garden Mosquito (HGM) traps were selected for evaluations at the University of Florida Horse Teaching Unit (HTU). Broodmares coated with fluorescent dust were either tethered to a post in the center of a paddock or released untethered into a paddock. HGM sticky traps were placed at the four compass points and four selected distances from the paddock center to capture stable flies before (unmarked) or after (marked) they visited the horses. More than 40% of flies captured on traps placed closest to the horses were marked. This indicates that the traps did not prevent the flies from visiting the horses. A percentage of marked and unmarked stable flies showed signs of blood in their guts indicating recent feeding. For unknown reasons, the number of stable flies marked with Signal Green dust exceeded the numbers marked with other colors. Although the HGM traps caught ample numbers of stable flies, the traps did not prevent stable flies from feeding on the horses. More work is needed to determine optimal trap placement and densities required to maximize stable fly management with traps.

Stomoxys calcitrans, mechanical vector of virulent Besnoitia besnoiti from chronically infected cattle to susceptible rabbit

Cattle besnoitiosis caused by Besnoitia besnoiti (Eucoccidiorida: Sarcocystidae) is a re-emerging disease in Europe. Its mechanical transmission by biting flies has not been investigated since the 1960s. The aim of this study was to re-examine the ability of Stomoxys calcitrans (Diptera: Muscidae) to transmit virulent B. besnoiti bradyzoites from chronically infected cows to susceptible rabbits. Three batches of 300 stable flies were allowed to take an interrupted bloodmeal on chronically infected cows, followed by an immediate bloodmeal on three rabbits (Group B). A control group of rabbits and a group exposed to the bites of non-infected S. calcitrans were included in the study. Blood quantitative polymerase chain reaction (qPCR) analyses, and clinical, serological and haematological surveys were performed in the three groups over 152 days until the rabbits were killed. Quantitative PCR analyses and histological examinations were performed in 24 tissue samples per rabbit. Only one rabbit in Group B exhibited clinical signs of the acute phase of besnoitiosis (hyperthermia, weight loss, regenerative anaemia and transient positive qPCR in blood) and was seroconverted. Parasite DNA was detected in four tissue samples from this rabbit, but no cysts were observed on histological examination. These findings indicate that S. calcitrans may act as a mechanical vector of B. besnoiti more efficiently than was previously considered.

Vector control efficacy of fly nets on preventing bovine leukemia virus transmission

Bovine leukemia virus (BLV) is horizontally transmitted among cattle through infected blood. This 3-year field study (2013-2016) aimed to confirm the potential of the blood-sucking stable fly as a risk factor of BLV transmission and to determine the efficacy of vector control on preventing the transmission of BLV. The BLV-positive conversion rate during summer was higher than that during winter in a model dairy farm, where many stable flies were observed during the summer. After fly nets were fixed onto the barn to prevent fly invasion, the BLV-positive conversion rate during the summer was significantly decreased compared with that in the absence of fly nets (P<0.01). These findings suggest that vector control using a fly net may inhibit BLV transmission.

Evaluation of a commercial vacuum fly trap for controlling flies on organic dairy farms

The objective of this study was to evaluate the efficacy of a commercial vacuum fly trap (CowVac, Spalding Laboratories, Reno, NV) in on-farm organic dairy production systems to control horn flies, stable flies, and face flies. As cows walk through the trap, flies are brushed off the face, flank, and back with hanging flaps and blown off the belly, udder, and legs from one side, and then vacuumed from the air into a chamber from vacuum inlets opposite the blower and above the cow. The study included 8 organic dairy farms during the summer of 2015 in Minnesota, and herds ranged from 30 to 350 cows in size. The farms were divided into pairs by location; during the first period of the summer (June to July), the trap was set up on 1 farm, whereas during the second period of the summer (August to September) the trap was sent to its paired farm. Farms were visited once per week to collect and count flies from the trap as well as count and record flies on cows. Bulk tank milk, fat, and protein production and somatic cell count were collected on farms during the entire study period. Data were analyzed using the GLM procedure of SAS (version 9.3, SAS Institute Inc., Cary, NC). Independent variables for analyses were the fixed effects of farm, trap presence, housing scenario, and summer period. Horn fly numbers on cows were lower by 44% on farm in the presence of a trap (11.4 vs. 20.5 flies/cow-side) compared with the absence of a trap. Stable fly (5.4 vs. 7.1 flies/leg) and face fly (1.0 vs. 1.0 flies/cow) numbers were similar on farm whether the trap was present or absent on farms, respectively. Milk production was similar for farms with the trap (15.5 kg/d) compared to without (15.3 kg/d) the trap. Bulk tank milk, milk components, and somatic cell count were statistically similar in the presence and absence of the trap, so potential benefits of the trap for those measures were not evident at low fly populations observed during the study. The presence of a trap on farm reduced horn fly population growth rates (-1.01 vs. 1.00 flies/d) compared with the absence of a trap. Cows on farms with no housing (100% pasture) tended to have reduced horn fly numbers (11.7 vs. 28.3 flies/cow-side) in the presence of a trap compared with the absence of a trap on farm. Cows on farms with housing had similar horn fly numbers (11.2 vs. 14.8 flies/cow-side) in the presence of a trap compared with the absence of a trap on farm. In summary, these results indicate the trap was effective in reducing horn fly numbers on cows and reduced horn fly growth rates during the pasture season in organic dairy production systems, but benefits in improved milk production were not evident likely because of relatively low fly populations.

Black Border Increases Stomoxys calcitrans Catch on White Sticky Traps

Stable fly, Stomoxys calcitrans, is a biting fly that can cause severe irritation to livestock resulting in reduced productivity. The most common method of monitoring S. calcitrans is through the use of sticky traps and many designs have been developed using different colours and materials such as alsynite fibreglass and polypropylene sheeting. Laboratory experiments and some field experimentation have demonstrated that colour contrast can attract S. calcitrans. However, this response has not been fully utilised in trap design. To test that simple colour contrast could increase trap efficacy, white sticky traps were mounted on three differently coloured backgrounds (white, yellow, and black) and positioned at five sites on a mixed livestock farm. White sticky traps on a black background caught significantly more S. calcitrans than the yellow or white backgrounds. An incidental result was that Pollenia sp. were caught in greater numbers on the yellow framed traps. The reasons for S. calcitrans attraction to black–white contrast are most likely due to conspicuousness in the environment although the extent to which flies are using this feature as a host-location cue or a perching site are unknown.

Identification of stable fly attractant compounds in vinasse, a byproduct of sugarcane-ethanol distillation

The stable fly, Stomoxys calcitrans (Diptera: Muscidae), is a worldwide pest of livestock. Recent outbreaks of stable flies in sugarcane fields in Brazil have become a serious problem for livestock producers. Larvae and pupae found inside sugarcane stems after harvesting may indicate that stable flies use these stems as potential oviposition or larval development sites. Field observations suggest that outbreaks of stable flies are associated with the vinasse and filter cake derived from biomass distillation in sugarcane ethanol production that are used as fertilizers in sugarcane fields. Adult stable flies are attracted to vinasse, which appears to present an ideal larval development site. The primary goal of the present study is to demonstrate the role of vinasse in influencing the sensory physiological and behavioural responses of stable flies, and to identify its associated volatile attractant compounds. Both laboratory and field studies showed that vinasse is extremely attractive to adult stable flies. Chemical analyses of volatiles collected revealed a wide range of carboxylic acids, alcohols, phenols and aldehydes as potential attractant compounds. These newly identified attractants could be used to develop a tool for the attractant-baited mass trapping of stable flies in order to reduce infestations.

Lethal Effects of the Insect Growth Regulator Cyromazine Against Three Species of Filth Flies, Musca domestica, Stomoxys calcitrans, and Fannia canicularis (Diptera: Muscidae) in Cattle, Swine, and Chicken Manure

The presence of various species of filth flies is a widespread problem where livestock, including poultry, are maintained and where manure accumulates. The house fly, Musca domestica L.; the stable fly, Stomoxys calcitrans (L.); and the little house fly, Fannia canicularis (L.) (each Diptera: Muscidae), the target pests in our study, can mechanically spread diseases, and S. calcitrans can bite cattle, causing losses in meat and milk production. Chemical control is widely used to suppress filth flies, but resistance to conventional insecticides has become problematic. Hence, an alternative approach, insect growth regulators (IGRs), has been adopted by many livestock producers. We assessed the ability of the IGR cyromazine in granular and granular-based aqueous formulations to suppress the three muscid species from developing in poultry, cattle, and swine manure collected from commercial livestock production facilities. Each of the two formulations provided either strong or complete control of the pests for the 4-wk duration of the study, excluding the granular formulation that provides control of only F. canicularis developing in poultry manure for 2 wk. The two cyromazine-based IGR formulations appear to be effective tools that, if rotated appropriately with other insecticides, can be incorporated into integrated pest management strategies for filth fly suppression.

Oviposition Deterrence and Immature Survival of Filth Flies (Diptera: Muscidae) When Exposed to Commercial Fungal Products

Filth flies are pests of livestock, and can transmit pathogens that cause disease to animals and their caretakers. Studies have shown successful infection of adult filth flies following exposure to different strains and formulations of entomopathogenic fungi. This study aimed to examine the effects of commercial formulations of Beauveria bassiana (Balsamo) (Moniliales: Moniliaceae) (i.e., BotaniGard ES, Mycotrol O, balEnce), and Metarhizium brunneum (Metsch.) (Ascomycota: Hypocreales) (i.e., Met52 EC), on filth fly oviposition and immature fly survival after exposure. House flies, Musca domestica L., laid significantly fewer eggs on Met52 EC-treated surfaces than on surfaces treated with all other products and the control. Similar numbers of eggs were laid on surfaces treated with all B. bassiana products, but egg production was half of the control. Stable flies, Stomoxys calcitrans (L.), laid the fewest eggs on Met52 EC- and Mycotrol O-treated surfaces. This species did not distinguish between the remaining products and the control. In a second experiment, house fly eggs were placed on treated cloths so that hatched larvae contacted the treatment prior to development. Met52 EC had the greatest effect on immature survival with a significant reduction in recovered pupae at the medium and high doses of fungi. Overall, Met52 EC, containing M. brunneum, had the greatest effect on house fly and stable fly oviposition deterrence and immature development of house flies. Management implications are discussed.

Enhanced repellency of binary mixtures of Calophyllum inophyllum nut oil fatty acids or their esters and three terpenoids to Stomoxys calcitrans

BACKGROUND

An assessment was made of the repellency to female stable flies of tamanu nut oil fatty acids or their esters alone (each 0.5 mg cm(-2) ) or in combination with cuminyl alcohol, cuminaldehyde and α-phellandrene (each 0.25 mg cm(-2) ), using an exposed human hand bioassay. Results were compared with those of synthetic repellent DEET (0.25 mg cm(-2) ).

RESULTS

Based upon protection time (PT) (time to first bite of stable fly), oleic acid, linoleic acid, methyl oleate or methyl linoleate synergised the repellency of each monoterpenoid and DEET. For example, the binary mixture of oleic acid and cuminyl alcohol (PT 2.05 h) resulted in significantly greater repellency than either oleic acid (0.55 h), cuminyl alcohol (0.70 h) or DEET alone (1.50 h). The binary mixtures of oleic acid and cuminyl alcohol or DEET (PT 2.10 h) did not differ significantly in repellency. The structure-activity relationship indicates that the degree of saturation, the side chain length and the functional group of fatty acids appear to play a role in determining the fatty acid repellency to stable flies.

CONCLUSION

Mixtures formulated from fatty acid and monoterpenoid could be useful as potential repellents for protecting humans and possibly domestic animals from bites caused by stable fly.

Effect of Mutual Interference on the Ability of Spalangia cameroni (Hymenoptera: Pteromalidae) to Attack and Parasitize Pupae of Stomoxys calcitrans (Diptera: Muscidae)

We investigated the effect of mutual interference on the attack efficiency and the rate of successful parasitism on the parasitoid Spalangia cameroni (Perkins) attacking pupae of the stable fly Stomoxys calcitrans (L.). Female parasitoids (2, 4, 8, 16, or 32) were exposed to 100 fly pupae during 24 h. The number of pupae that were attacked and the number successfully parasitized increased with the parasitoid density and reached a maximum of ∼70 and 50, respectively. Parasitoid-induced mortality (PIM) was about 20 pupae, irrespective of parasitoid density. The per capita rates of attack, successful parasitism and parasitoid-induced mortality declined monotonously with parasitoid density. Progeny sex ratio was female biased for all parasitoid densities, but declined significantly with increasing parasitoid density from ∼70% females at the lowest density to ∼60% at the highest. Mutual interference was incorporated into a functional response model to predict the attack rate and the rate of successful parasitism at different temperatures, host densities and parasitoid densities. The model explained 93.5% of the variation in the observed number of attacked pupae and 91.5% of the variation in the number of successfully parasitized pupae. The model predicts that increasing parasitoid densities will increase the percentage of killed hosts, but only up to a certain density. Above this density, a further increase in parasitoid abundance will actually lead to a decline in the percentage parasitism. These findings may have some implications for using S. cameroni in biological control against flies using inundative releases.

Temperature-Dependent Functional Response of Spalangia cameroni (Hymenoptera: Pteromalidae), a Parasitoid of Stomoxys calcitrans (Diptera: Muscidae)

The effects of host density, temperature, and burial depths on the functional response of the synovigenic parasitoid Spalangia cameroni (Perkins) attacking pupae of the stable fly Stomoxys calcitrans (L.) were examined. Five temperatures (15, 20, 25, 30, and 35°C), six host densities (2, 4, 8, 16, 32, and 64 pupae per 19.64 cm(2)), and three burial depths in whole wheat grains (0, 8, and 16 cm) were used. It was demonstrated that temperature had a profound effect on the functional response, whereas burial depths of the pupae played a minor role. For all temperatures, the functional response was of type 2 with an upper asymptote that depends on the temperature. Data were fitted by a functional response model where only the maximum attack rate is temperature dependent. The model shows that the optimal temperature for S. cameroni for attacking S. calcitrans pupae is 28.6°C, where the maximum attack rate is 20.2 pupae day(-1). The lower and upper temperature thresholds for attacks were found as 8.1 and 36.6°C, respectively. The temperature range for attacks that resulted in successful parasitism was narrower, namely, 15.0 and 35.5°C. Maximum rate of successful parasitism was estimated to be 18.2 progeny day(-1) occurring at 27.9°C. The proportion of attacks resulting in successful parasitism increased steeply with temperatures >15°C and declined steeply at temperatures >30°C.

Temporal changes in the bacterial community of animal feces and their correlation with stable fly oviposition, larval development, and adult fitness

Stable flies are blood-feeding insects with a great negative impact on animals world wide. Larvae develop primarily in animal manure and bacteria are essential for larval development; however, the principle of this dependence is not understood. We hypothesized that as the microbial community of animal manure changes over time, it plays an important role in stable fly fitness. Two-choice bioassays were conducted using 2 week old horse manure (control) and aging horse manure (fresh to 5 week old) to evaluate the effect of manure age on stable fly oviposition. Our data showed that fresh feces did not stimulate oviposition and that the attractiveness increased as manure aged but started to decline after 3 weeks. Bioassays assessing the effect of manure age at the time of oviposition on larval development demonstrated that 1–3 week old manure supported larval development significantly better than fresh, 4, and 5 week old manure. In addition, adult fitness (body size) was significantly higher in flies from 1 and 2 week old manure comparing to that of all other treatments. Analysis of the bacterial community of aging horse manure by 454-pyrosequencing of 16S rDNA revealed a great reduction in bacterial diversity and richness from fresh to 1–5 week old manure and a major shift from strict anaerobes in fresh manure to facultative anaerobes and strict aerobes in aged manure. Overall, the microbial community of 2 and 3 week old horse manure with its dominant bacterial taxa Rhizobium, Devosia, and Brevundimonas stimulated stable fly oviposition the most and provided a suitable habitat for larval development. These bacteria represent the candidates for studies focused on better understanding of stable fly – microbial interactions.

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 $72 per season at commercial rates of $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.

The repellency of lemongrass oil against stable flies, tested using video tracking

Lemongrass oil (Cymbopogon citratus) is an effective repellent against mosquitoes (Diptera: Culicidae) and house flies (Diptera: Muscidae). In this study, its effectiveness was assessed on stable flies (Diptera: Muscidae) in laboratory conditions. First, we demonstrated that lemongrass oil is an active substance for antennal olfactory receptor cells of Stomoxys calcitrans as indicated by a significant increase in the electroantennogram responses to increasing doses of lemongrass oil. Feeding-choice tests in a flight cage with stable flies having access to two blood-soaked sanitary pads, one of which was treated with lemongrass oil, showed that stable flies (n = 24) spent significantly more time in the untreated zone (median value = 218.4 s) than in the treated zone (median value = 63.7 s). No stable flies fed on the treated pad, whereas nine fed on the untreated pad. These results suggest that lemongrass oil could be used as an effective repellent against stable flies. Additional studies to confirm its spatial repellent and feeding deterrent effects are warranted.

An insight into the transcriptome and proteome of the salivary gland of the stable fly, Stomoxys calcitrans

Adult stable flies are blood feeders, a nuisance, and mechanical vectors of veterinary diseases. To enable efficient feeding, blood sucking insects have evolved a sophisticated array of salivary compounds to disarm their host's hemostasis and inflammatory reaction. While the sialomes of several blood sucking Nematocera flies have been described, no thorough description has been made so far of any Brachycera, except for a detailed proteome analysis of a tabanid (Xu et al., 2008). In this work we provide an insight into the sialome of the muscid Stomoxys calcitrans, revealing a complex mixture of serine proteases, endonucleases, Kazal-containing peptides, anti-thrombins, antigen 5 related proteins, antimicrobial peptides, and the usual finding of mysterious secreted peptides that have no known partners, and may reflect the very fast evolution of salivary proteins due to the vertebrate host immune pressure. Supplemental Tables S1 and S2 can be downloaded from http://exon.niaid.nih.gov/transcriptome/S_calcitrans/T1/Sc-tb1-web.xls and http://exon.niaid.nih.gov/transcriptome/S_calcitrans/T2/Sc-tb2-web.xls.