Efficacy and longevity of newly developed catnip oil microcapsules against stable fly oviposition and larval growth

The stable fly, Stomoxys calcitrans (Diptera: Muscidae), is one of the most important pests of cattle and costs U.S. cattle producers billions of dollars in losses annually. In this study, the efficacy of catnip oil encapsulated in gelatin in oviposition deterrence and larval growth inhibition in stable flies was examined under laboratory conditions. More than 98% inhibition of stable fly larval growth and female oviposition was observed in larval and oviposition media treated with encapsulated catnip oil (0.5 g). Further, dose–response tests showed that as little as 0.1 g of encapsulated catnip oil provided > 85% oviposition deterrence. The release of nepetalactones from the capsules was more rapid when the capsules were placed on a moist substrate rather than a dry substrate. Encapsulated catnip oil also exhibited antibacterial activity, supporting the hypothesis that its inhibition of larval growth may be based on its killing of the bacteria on which larvae feed. The use of encapsulated catnip oil can provide an alternative control strategy for stable fly management.     

Efficacy and safety of catnip (Nepeta cataria) as a novel filth fly repellent*

Catnip (Nepeta cataria) is known for its pseudo‐narcotic effects on cats. Recently, it has been reported as an effective mosquito repellent against several Aedes and Culex species, both topically and spatially. Our laboratory bioassays showed that catnip essential oil (at a dosage of 20 mg) resulted in average repellency rates of 96% against stable flies, Stomoxys calcitrans (L.) and 79% against houseflies, Musca domestica (L.), respectively. This finding suggested that the application of repellent could be used as part of filth fly management. Further evaluations of catnip oil toxicity were conducted to provide a broad‐spectrum safety profile of catnip oil use as a potential biting and nuisance insect repellent in urban settings. Acute oral, dermal, inhalation, primary dermal and eye irritation toxicity tests were performed. The acute oral LD₅₀ of catnip oil was found to be 3160 mg/kg body weight (BW) and 2710 mg/kg BW in female and male rats, respectively. The acute dermal LD₅₀ was > 5000 mg/kg BW. The acute inhalation LD₅₀ was observed to be > 10 000 mg/m³. Primary skin irritation tested on New Zealand white rabbits showed that catnip oil is a moderate irritant. Catnip oil was classified as practically non‐irritating to the eye. In comparison with other U.S. Environmental Protection Agency‐approved mosquito repellents (DEET, picaridin and p‐menthane‐3,8‐diol), catnip oil can be considered as a relatively safe repellent, which may cause minor skin irritation.     

Catnip,Nepeta cataria, a morphological comparison of mutant and wild type specimens to gain an ethnobotanical perspective

Nepeta cataria L, the catnip plant, is important in the pet industry for cats and as an herbal medicinal treatment for the fevers, diarrhea, insomnia, and lacking menstruation of humans. A natural mutation of N. cataria produced a novel morphology that warranted investigation to determine how the mutation affected the microscopic features, including catnip’s ethnobotanical storehouse of glandular hairs. The morphology, anatomy, and physiology of this mutant are compared to that of the wild type of catnip to document the major differences. The secondary plant metabolites which facilitate catnip’s ethnobotanical uses are stored in microscopic glandular hairs (trichomes). The trichomes on the mutant and wild type catnip leaves were not shown to differ (scanning and transmission electron microscopy). The feliobotany (use by cats) of N. cataria is discussed in relation to catnip trichomes.     

Larval experience of stable fly,Stomoxys calcitrans Linneaus, 1758 (Diptera: Muscidae) does not influence oviposition preference in gravid females

1. Hopkins' host selection principle (HHSP) proposes that, in holometabolous insects, gravid females prefer to oviposit on their developmental substrate. This hypothesis is widely explored in phytophagous insects, but few studies have considered blood‐feeding insects. In this study, the HHSP was tested using the haematophagous stable fly, Stomoxys calcitrans (Diptera: Muscidae). Using no‐choice and two‐choice tests, the study first sought to demonstrate whether S. calcitrans larvae recognise their rearing substrate. 2. It was found that when a rearing substrate is offered to S. calcitrans larvae singly (no‐choice) or associated with a non‐rearing substrate (two‐choice), they were able to recognise the substrate in which they developed. This ability disappeared when larvae were transferred to another substrate for 5 h. 3. Next, using oviposition bioassays, it was investigated whether information gathered by pre‐imaginal stages during their development can persist into the adult stages after metamorphosis. It was hypothesised that gravid females emerging from clean and uncleaned pupae reared on sheep and camel dung would still prefer to lay on their rearing substrate. The results revealed that gravid females did not prefer to oviposit on their developmental substrate. In addition, failure to recognise and prefer their developmental substrate was found in gravid females that had emerged from puparia that were cleaned as well as those contaminated with sheep dung. 4. It is concluded that S. calcitrans adult preference is not influenced by their offspring's experience. Overall, the HHSP was not supported by our study, suggesting that this principle may not apply to generalist insects characterised by high plasticity in oviposition substrate acceptance.     

Quantification of nepetalactones in catnip (Nepeta cataria L.) by HPLC coupled with ultraviolet and mass spectrometric detection

Nepetalactones, the major chemical components of catnip (Nepeta cataria L.), were analysed by reversed-phase HPLC coupled with UV and MS detection. Two major nepetalactones, Z,E-nepetalactone and E,Z-nepetalactone, were successfully identified and quantified. The linearity range for Z,E-nepetalactone was determined as 0.00655-0.655 mg/mL with a correlation coefficient of 0.9999, and the linearity range of E,Z-nepetalactone was found to be 0.00228-0.456 mg/mL with a correlation coefficient of 0.9999, under UV detection at 228 nm. The linearity ranges were from 0.00164 to 0.0328 mg/mL, with a correlation coefficient of 0.9999, for ZE-nepetalactone and 0.00114-0.0228 mg/mL, with a correlation coefficient of 0.9999, for E,Z-nepetalactone by MS detection with selected ion monitoring of ion peak m/z 167. The MS detection was found to be more sensitive than UV detection and this method was validated as simple, reliable and sensitive for catnip nepetalactone analysis. This method can be used for identification and fingerprinting of catnip products.     

Diethylphenylacetamide: a new insect repellent against stable fly,Stomoxys calcitrans

Abstract. This paper reports the results of a laboratory study showing effectiveness of a new insect repellent N,N-diethylphenylacetamide (DEPA) against stable fly, Stomoxys calcitrans, and compared to N,N-diethyl-m-toluamide (DEET) and dimethyl-phthalate (DMP). DEPA gave maximum protection time of more than 6h at 3% concentration followed by DEET and DMP.     

Role of bacteria in the oviposition behaviour and larval development of stable flies

Stable flies, Stomoxys calcitrans (L.), are the most important pests of cattle in the United States. However, adequate management strategies for stable flies, especially for pastured cattle, are lacking. Microbial/symbiont-based approaches offer novel venues for management of insect pests and/or vector-borne human and animal pathogens. Unfortunately, the fundamental knowledge of stable fly-microbial associations and their effect on stable fly biology is lacking. In this study, stable flies laid greater numbers of eggs on a substrate with an active microbial community (> 95% of total eggs oviposited) than on a sterilized substrate. In addition, stable fly larvae could not develop in a sterilized natural or artificial substrate/medium. Bacteria were isolated and identified from a natural stable fly oviposition/developmental habitat and their individual effect on stable fly oviposition response and larval development was evaluated in laboratory bioassays. Of nine bacterial strains evaluated in the oviposition bioassays, Citrobacter freundii stimulated oviposition to the greatest extent. C. freundii also sustained stable fly development, but to a lesser degree than Serratia fanticola. Serratia marcescens and Aeromonas spp. neither stimulated oviposition nor supported stable fly development. These results demonstrate a stable fly bacterial symbiosis; stable fly larval development depends on a live microbial community in the natural habitat, and stable fly females are capable of selecting an oviposition site based on the microbially derived stimuli that indicate the suitability of the substrate for larval development. This study shows a promising starting point for exploiting stable fly-bacterial associations for development of novel approaches for stable fly management.     

Effects of pyriproxyfen and buprofezin on immature development and reproduction in the stable fly*

The stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), is one of the most significant biting flies that affect cattle. The use of traditional insecticides for stable fly control has only a limited success owing to the insect's unique feeding behaviours and immature development sites. A laboratory study was conducted to evaluate the effects of two insect growth regulator (IGR) products, pyriproxyfen and buprofezin, on the development of the immature stages of the stable fly and the effects of pyriproxyfen on oviposition and egg hatch. Both pyriproxyfen and buprofezin had significant inhibitory effects on immature development. The LC₅₀s of pyriproxyfen and buprofezin were 0.002 and 18.92 p.p.m., respectively. Topical treatment of adult females with different doses of pyriproxyfen had significant negative effects on both female oviposition and egg hatching when 1‐ and 3‐day‐old females were treated, and the effects were dose dependent. A significant reduction in the mean number of eggs laid was observed only at the highest pyriproxyfen dose (8 µg/fly) and egg hatch was unaffected by pyriproxyfen treatment when 5‐day‐old females were treated. Results from the present study indicate that pyriproxyfen has the potential to be used as part of an integrated stable fly management programme.     

N-acetylglucosaminyl transferases from the pupal instar of the stable fly,Stomoxys calcitrans

N-acetylglucosaminyl transferases from pupae of Stomoxys calcitrans (L.) were studied in 10,000g pellet suspensions. Characterization of these enzymes was based on formation of glycolipids (ie, Dol·PP-GlcNAc and Dol·PP-(GlcNAc)₂), oligosaccharide lipids, and giycoproteins. Studies on transferase activity during the pupal instar showed that there were two peaks of activity; the first peak was on day 0 (prepupae) and the second at 3 days after pupation. Subcellular fractionation indicated that 10,000g and 100,000g pellets contained most of the transferase activities. The transferases required divalent cations (either Mn²⁺ or Mg²⁺). The pH optimum, which varied for each of the products formed, was 7.5 for glycolipids, 7.0 for oligosaccharide lipids, and 6.5 for glycoprotein. Inclusion of dolichol monophosphate doubled the amount of Dol·PP-GlcNAc and Dol·PP·(GlcNAc)₂ formed, but had little effect on oligosaccharide lipid and glycoprotein formation. Tunicamycin was a potent inhibitor of glycolipid formation with an I₅₀ of 1.8–4.8 nM. It was confirmed that tunicamycin acts by preventing the transfer of GlcNAc-1-P from UDP-GlcNAc to Dol·P. UMP reverses glycolipid formation, yielding UDP-GlcNAc. Some characterization of the products was performed. Glycolipids were shown to be Dol·PP-GlcNAc and Dol·PP-(GlcNAc)₂. Glycoprotein was rapidly solubilized by protease and detergent treatments, whereas oligosaccharide lipids appeared to be acid-labile, pyrophosphate-containing lipids. The apparent kinetic constants for the formation of glycolipids were as follows: UDP-GlcNAc K_m = 1.55 ± 0.47 μM, V_max = 0.66 ± 0.21 pmol·min^?1·mg^?1; Dol·P K_m = 2.08 ± 0.85 μM, V_max = 0.13 ± 0.06 pmol·min^?1·mg^?1 protein.     

Electroantennogram responses of the stable fly, Stomoxys calcitrans, to carbon dioxide and other odours

ABSTRACT. Electroantennograms (EAGs) were recorded from Stomoxys calcitrans (L.) in response to increasing concentrations of carbon dioxide in an airstream. The magnitude of the EAG increases logarithmically from +0.023% carbon dioxide up to approximately +2.0% where a maximum is reached. Flies deprived of food for 48–50 h are more responsive to small increases in the carbon dioxide concentration than those deprived of food for only 20–23 h. It is concluded that the sensitivity of carbon dioxide receptors on the antennae of S. calcitrans increases as hunger develops. EAGs were also recorded in response to cattle odour, odour from fresh cattle faeces, expired human breath, acetone, and l-octen-3-ol. Acetic acid vapour causes a reversal of the usual EAG response indicating inhibition.     

Sensory and behavioural responses of the stable fly Stomoxys calcitrans to rumen volatiles

Analysis of volatiles from rumen digesta by gas chromatography linked antennogram recordings from Stomoxys calcitrans (L) (Diptera: Muscidae) antennal receptor cells revealed about 30 electrophysiologically active constituents, the most important of which is dimethyl trisulphide with a sensory threshold in the femtogram range. The behavioural responses of S. calcitrans to five chemostimulants (dimethyl trisulphide, butanoic acid, p-cresol, oct-1-en-3-ol and skatole) were tested in a wind tunnel where activation and attraction of hungry flies to rumen volatiles were recorded. Dimethyl trisulphide, butanoic acid and p-cresol were found to attract S. calcitrans. This sensitivity to rumen volatile constituents, that also occur in animal wastes used for oviposition by Stomoxys spp., as well as in flowers used by stable flies as sources of nectar is discussed in the context of the behavioural ecology of these flies.     

Genetic variability of the stable fly assessed on a global scale using amplified fragment length polymorphism

The stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), is a blood‐feeding, economically important pest of animals and humans worldwide. Improved management strategies are essential and their development would benefit from studies on genetic diversity of stable flies. Especially if done on a global scale, such research could generate information necessary for the development and application of more efficient control methods. Herein we report on a genetic study of stable flies using amplified fragment length polymorphism, with samples of 10–40 individuals acquired from a total of 25 locations in the Nearctic, Neotropic, Palearctic, Afrotropic and Australasian biogeographical regions. We hypothesized that genetic differentiation would exist across geographical barriers. Although F_ST (0.33) was moderately high, the G_ST (0.05; representing genetic diversity between individuals) was very low; N_m values (representing gene flow) were high (9.36). The mismatch distribution and tests of neutrality suggested population expansion, with no genetic differentiation between locations. The analysis of molecular variance (AMOVA) results showed the majority of genetic diversity was within groups. The mantel test showed no correlation between geographic and genetic distance; this strongly supports the AMOVA results. These results suggest that stable flies did not show genetic differentiation but are panmictic, with no evidence of isolation by distance or across geographical barriers.     

Improved capture of stable flies (Diptera: Muscidae) by placement of knight stick sticky fly traps protected by electric fence inside animal exhibit yards at the Smithsonian's National Zoological Park

Stable flies are noxious blood‐feeding pests of exotic animals at zoological parks, inflicting painful bites, and causing discomfort to animals. Stable fly management is difficult because of the flies’ tendency to remain on the host animals only when feeding. Non‐toxic traps can be efficient but traps placed around exhibit perimeters captured fewer‐than‐expected numbers of flies. By surrounding traps with square electric fence enclosures, traps could be placed in the exhibits with the host animals and compared with an equal number of traps placed along perimeter fences. During a 21‐week study, traps inside exhibits captured 5× more stable flies than traps placed along exhibit perimeters. Traps inside exhibits tended to show more fluctuations in fly populations than traps along perimeters. The increased numbers of flies captured using this technique should provide relief from this pestiferous fly and greatly improve animal health and welfare. We believe this to be the first study where traps were used to capture stable flies in exhibit yards at a zoological park.     

Feeding response of the stable fly, Stomoxys calcitrant L., to blood fractions and adenine nucleotides

Abstract Feeding responses of the stable fly ( Stomoxys calcitrans L., Diptera: Muscidae) to blood fractions and saline-based diets were studied in an artificial feeding device. Flies fed equally on whole blood, plasma and erythrocyte fractions while resuspended platelets or the buffy layer did not stimulate feeding. Evidence from filtration studies indicates that plasma contains both less-than-5000D and greater-than-100,000D phagostimulatory components. ATP, ADP and AMP in saline stimulate feeding in this insect in a dose-dependent manner. cAMP also stimulates feeding in the range of concentrations tested. It is argued that the less-than-5000D phagostimulant may be one or more of these adenine nucleotides.     

Effects of carbon dioxide, acetone and 1-octen-3-ol on the flight responses of the stable fly, Stomoxys calcitrans, in a wind tunnel

Abstract. The flight behaviour of Stomoxys calcitrans (L.) in odour plumes containing carbon dioxide, acetone or l-octen-3-ol was assessed from video recordings. A downwind bias was evident in clean air, whereas all three test chemicals elicited upwind anemotaxis. Response thresholds were ∼0.006% for CO2, between 0.001 and 0.01 μg/l for acetone, and ∼0.0002 u.g/1 for l-octen-3-ol. Sinuosity (° cm^-1) and angular velocity (° s^-1) increased with C0₂ concentration, but velocity (cm s"¹) decreased. Similar, but less clear effects were observed for acetone and l-octen-3-ol.     

Effects of carbon dioxide, acetone and 1-octen-3-ol on the activity of the stable fly, Stomoxys calcitmns

Abstract. The responses of Stomoxys calcitrans (L.) to carbon dioxide, acetone and 1-octen-3-ol were assessed using flight activity as a measure of activation. Carbon dioxide and acetone caused significant increases in activity, with thresholds at -0.006% and -0.01 μg 1^-l, respectively. For l-octen-3-ol, flight activity decreased at 2 μg 1^-1 for males, and at 0.2 μg 1^-1 for females. Variation in activity was also manifest as differences in the time elapsed between landing and subsequent take-off: CO₂ (7.1 s) and acetone (12.2s) had lower times than the corresponding no-odour controls (16.6 and 23.2s), whereas 1-octen-3-ol (25 s) had a higher time than the control (21.5 s). The proportion of the total number of flights landing on a black target was higher in CO₂(0.16) and acetone (0.11) than in clear air (c. 0.07), but was lower for l-octen-3-ol.     

High relative abundance of the stable fly Stomoxys calcitrans is associated with lumpy skin disease outbreaks in Israeli dairy farms

The vector of lumpy skin disease (LSD), a viral disease affecting Bovidae, is currently unknown. To evaluate the possible vector of LSD virus (LSDV) under field conditions, a yearlong trapping of dipterans was conducted in dairy farms that had been affected by LSD, 1‐2 years previously. This was done in order to calculate monthly relative abundances of each dipteran in each farm throughout the year. The relative abundances of Stomoxys calcitrans (Diptera: Muscidae) in the months parallel to the outbreaks (December and April) were significantly higher than those of other dipterans. A stable fly population model based on weather parameters for the affected area was used to validate these findings. Its results were significantly correlated with S. calcitrans abundance. This model, based on weather parameters during the epidemic years showed that S. calcitrans populations peaked in the months of LSD onset in the studied farms. These observations and model predictions revealed a lower abundance of stable flies during October and November, when LSD affected adjacent grazing beef herds. These findings therefore suggest that S. calcitrans is a potential vector of LSD in dairy farms and that another vector is probably involved in LSDV transmission in grazing herds. These findings should be followed up with vector competence studies.     

Repellent effects of pongam oil on settlement and oviposition of the common greenhouse whitefly Trialeurodes vaporariorum on chrysanthemum

The repellent activities, including host deterrence and anti-oviposion, of pongam oil against the adults of the common greenhouse whitefly Trialeurodes vaporariorum Westwood in greenhouses were tested. Chrysanthemum plants treated with different concentrations （0.5%-2.0%） of water-suspended pongam oil showed relatively long-lasting host deterrent and anti-oviposition effects on the adults of greenhouse whitefly. Although the repellent effect declined in time and concentration, strong effects on the reduction of oviposition were found, which lasts, dependent on concentration at least 12 days after application.     

猫薄荷精油有效成分的提取及其对白纹伊蚊、淡色库蚊的驱避活性

采用同时蒸馏萃取及硅胶柱层析法从猫薄荷Nepeta cataria 植物中提取、分离制得驱蚊有效成分假荆芥内酯,并采用个体涂肤有效保护时间测定法及风洞空间驱避效果测试法, 对假荆芥内酯与避蚊胺(DEET)的驱蚊效果进行了对比试验。结果表明,400 g新鲜猫薄荷植株可制得精油5.6 g,其中假荆芥内酯含量为55%,Z,E-假荆芥内酯32%, E,Z-假荆芥内酯23%。室内标准药效评价结果表明,DEET对白纹伊蚊Aedes albopictus 及淡色库蚊Culex pipiens pallens有效保护时间分别为9.6±0.2 h与11.5±1.5 h,而假荆芥内酯仅为2.2±0.2 h与4.3±0.8 h。风洞定向行为测试结果表明,假荆芥内酯单独作用时,对蚊虫有微弱的引诱效果,但在人体气味及二氯甲烷L-乳酸存在时,可显著抑制这些引诱物对蚊虫的引诱效果,是优良的空间驱避剂;DEET对蚊虫无明显的引诱作用,对二氯甲烷L-乳酸溶液引诱剂也无明显的抑制效果,但可显著增强人体气味对蚊虫的引诱性。