Effects of four commercial fungal formulations on mortality and sporulation in house flies (Musca domestica) and stable flies (Stomoxys calcitrans)

The house fly Musca domestica L. (Diptera: Muscidae) and stable fly Stomoxys calcitrans (L.) (Diptera: Muscidae) are major pests of livestock. Biological control is an important tool in an integrated control framework. Increased mortality in filth flies has been documented with entomopathogenic fungi, several strains of which are commercially available. Three strains of Beauveria bassiana (Balsamo‐Crivelli) Vuillemin (Hypocreales: Cordycipitaceae) and one strain of Metarhizium brunneum (Petch) (Hypocreales: Clavicipitaceae) were tested in commercial formulations for pathogenicity against house flies and stable flies. There was a significant increase in mortality of house flies with three of the formulations, BotaniGard^® ES, Mycotrol^® O, and Met52^® EC, during days 4–9 in comparison with balEnce? and the control. In stable flies, mortality rates were highest with Met52^® EC, followed by Mycotrol^® O, BotaniGard^® ES and, finally, balEnce?. There was a significant fungal effect on sporulation in both house flies and stable flies. Product formulation, species differences and fungal strains may be responsible for some of the differences observed. Future testing in field situations is necessary. These commercial biopesticides may represent important tools in integrated fly management programmes.     

Biological control of <Emphasis Type="Italic">Musca domestica</Emphasis> and <Emphasis Type="Italic">Stomoxys calcitrans</Emphasis> by mass releases of the parasitoid <Emphasis Type="Italic">Spalangia cameroni</Emphasis> on two Norwegian pig farms

House flies (Musca domestica L.) and stable flies (Stomoxys calcitrans (L.)) (Diptera: Muscidae) are nuisance pests on livestock farms. In the present study we tested the effect of biweekly mass release of Spalangia cameroni Perkins (Hymenoptera: Pteromalidae), the most common parasitoid of house flies and stable flies in southern Norway, on pig premises with scattered fly breeding sites. The study spanned two successive summer periods, with two control and two release units each year. Spalangia cameroni suppressed both house flies and stable flies in one release unit during the first year, and stable flies in one release unit the second year. The apparent lack of success in fly control in the other release units was likely due to immigration of flies in two of the trials and high temperatures in one trial. Recommendations concerning release of S. cameroni in similar pig production premises are given. Handling editor: Torsten Meiners.     

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.     

Laboratory studies on the biology ofSpalangia nigra [Hym.: Pteromalidae]

At 21 °C,Spalangia nigra Latreille (Hymenoptera: Pteromalidae) averaged 29.3 days between exposure and emergence of 1^st progeny from host house flies,Musca domestica L. (Diptera: Muscidae). At 27 °C, the average developmental time to 1^st emergence was reduced to 26.6 days, and a majority of adult wasps emerged from host house fly puparia between 29 and 40 days postoviposition. The sex ratio of progeny ranged from 1.4 to 1.8 female-to-male, but all progeny of virgin females were male. Male wasps lived from 6.8–15 and females 11–17.8 days at 27 °C; honey as a food source increased longevity. No significant differences in parasitism byS. nigra were associated with host house fly pupal densities ranging from 1 to 200 pupae per female-male pair of wasps, but average percent parasitism decreased at host densities greater than 50. House fly pupae exposed to parasitism at ages ranging from 4 to 96 h did not differ in subsequent production of adult flies.S. nigra did not demonstrate preference for house flies or stable flies,Stomoxys calcitrans (L.) (Diptera: Muscidae) as hosts. The results of these studies indicate thatS. nigra may contribute significantly to previously unexplained mortality of house flies and stable flies.      

Does behaviour play a role in house fly resistance to imidacloprid‐containing baits?

The objective of this research was to examine the role and type of behavioural mechanisms that function in house fly, Musca domestica L. (Diptera: Muscidae), resistance to an imidacloprid‐containing commercial fly bait, QuickBayt^®, using an insecticide‐susceptible and an imidacloprid‐resistant strain. Mortality and feeding behaviour were observed through choice bioassays of three post‐imidacloprid selected house fly generations to determine whether flies would consume the bait in the presence of an alternative food source. Mortality rates in choice containers progressively decreased in post‐selection flies as QuickBayt^® no‐choice selections proceeded. There were no differences between the proportions of flies observed contacting QuickBayt^® and sugar, respectively, a finding that eliminates repellency as a mechanism of stimulus‐dependent behavioural resistance. However, differences in QuickBayt^® consumption and subsequent mortality between choice and no‐choice containers provided strong support for the evolution of consumption irritancy‐ or taste aversion‐related behavioural resistance. The results of this study support the responsible rotation of insecticide bait formulations for house fly control.     

Activity of pupal parasitoids of the stable fly Stomoxys calcitrans and prevalence of entomopathogenic fungi in the stable fly and the house fly Musca domestica in Denmark

A survey was conducted on confined dairy cattle farms and a pig farm from May–October in 1999 to determine the activity and relative abundance of pupal parasitoids and the prevalence of entomopathogenic fungi in populations of the haematophagous stable fly, Stomoxys calcitrans (Diptera: Muscidae), in Denmark. Four species of pteromalids were found with Spalangia cameroni as the predominant. The other parasitoids were S. nigripes, S. nigra and Phygadeuon fumator (Ichneumonidae). Peak activity of the parasitoids was observed to be late in the summer and the beginning of autumn (August–September) when approximately 10% of the collected stable fly pupae were parasitised. Adult stable flies were infected with four species of entomopathogenic fungi: Entomophthora muscae, E. schizophorae, Beauveria bassiana and Verticillium lecanii. All fungi occurred in low percentages (max. 4%) and remained at this level throughout the sampling period. Likewise, adult house flies were infected with B. bassiana and V. lecanii,but Metarhizium anisopliae, Paecilomyces fumosoroseus and V. fusisporum were also recorded. The overall hyphomycete prevalence in house flies was 0.3%, and single species rarely exceeded 0.1%. The prevalence remained low in spite of increasing house fly numbers in August–September.     

Ovipositing female house flies provision offspring larvae with bacterial food

Symbiotic bacteria on house fly eggs, Musca domestica L. (Diptera: Muscidae), provide ovipositional cues for conspecific female flies and curtail the growth of fungi that compete with fly larval offspring for resources. Because bacteria are also essential dietary constituents for developing larvae, we tested the hypothesis that egg‐derived bacteria support development of larvae to adults. From house fly eggs, we isolated and identified 12 strains of bacteria, eight and four of which were previously shown to induce and inhibit oviposition, respectively. When larvae were provisioned with a total dose of 10⁶–10⁷ colony‐forming units of bacteria from either the oviposition‐inducing or inhibiting group, or from both groups together, significantly more larvae completed development. Thus, egg‐associated bacteria could be a fail‐safe mechanism that ensures a bacterial food supply for larval offspring, particularly if the resource selected by parent females is poor in bacterial food.     

Determination of the Genetic and Synergistic Suppression of a Methoxyfenozide-Resistant Strain of the House Fly <Emphasis Type="Italic">Musca domestica</Emphasis> L. (Diptera: Muscidae)

Musca domestica Linnaeus (house fly, Diptera: Muscidae) is a major veterinary and medical important pest all over the world. These flies have ability to develop resistance to insecticides. The present trial was performed to discover the inheritance mode (autosomal, dominance, number of genes involved) and preliminary mechanism of methoxyfenozide resistance in order to provide basic information necessary to develop resistance management strategy for this pest. A strain of M. domestica (MXY-SEL) was exposed to methoxyfenozide for 44 generations which developed a 5253.90-fold level of resistance to methoxyfenozide. The overlapping fiducial limits of LC₅₀ values of the reciprocal crosses, F₁ (MXY-SEL ♂?×?Susceptible ♀) and F₁^? (MXY-SEL ♀?×?Susceptible ♂), suggest that inheritance of methoxyfenozide resistance was an autosomal and likely completely dominant trait (D_LC?=?0.93 and 0.94 for F₁ and F₁^?, respectively). Backcrosses of the F₁ with the parental MXY-SEL or Susceptible population predict a polygenic mode of inheritance. Piperonyl butoxide significantly altered the LC₅₀ values, suggesting enhanced detoxification by cytochrome P450-dependent monooxygenases is a major mechanism of resistance to methoxyfenozide in the MXY-SEL strain. The estimated realized heritability was 0.07 for methoxyfenozide. These results would be helpful for the better management of M. domestica.     

Chemical composition and larvicidal activity of essential oils of three Artemisia species

Aedes aegypti L. (Diptera: Culicidae) is a vector for serious diseases in tropical regions. This pest is mainly controlled by commercial larvicides but the application of such products has led to environmental problems. Essential oils (EO) have been consistently reported as molecules with insecticidal activity and can be used to produce more environmentally friendly larvicides in the control of A. aegypti. In this study, the larvicidal effect of essential oils (EO) from the leaves of three Artemisia species was evaluated against A. aegypti. The oils were obtained from steam distillation and their chemical composition was determined by gas chromatography–mass spectrometry. The EO of Artemisia camphorata was the most active in the screening bioassay and presented LC₅₀ and LC₉₅ of 64.95 and 74.18 μg ml⁻¹, respectively. In addition, we found that germacrene D-4-ol was the constituent responsible for the toxicity of this EO. Artemisia camphorata EO and its major constituent, germacrene D-4-ol, are promising for the development of natural larvicides against A. aegypti.     

Sublethal effects of imidacloprid exposure on <Emphasis Type="Italic">Spalangia endius</Emphasis>, a pupal parasitoid of filth flies

Parasitoids and neonicotinoids can both suppress economically harmful filth fly populations. However, sublethal effects of neonicotinoids have not previously been studied for commonly used species of filth fly parasitoids. Exposure to an LC₅₀ of imidacloprid decreased the ability of surviving individuals of the parasitoid wasp Spalangia endius Walker (Hymenoptera: Pteromalidae) to kill house fly pupae under some conditions. In an unburied-hosts experiment, significantly more flies and fewer parasitoids emerged in the LC₅₀ imidacloprid treatment versus the LC₁₀ or controls. Parasitoid sex ratio and longevity were not affected. However, in a buried-hosts experiment, parasitoid and fly emergence were independent of treatment. ELISA (enzyme-linked immunosorbent assay) showed lower imidacloprid residues in or on parasitoids exposed to the media in which hosts were buried. Our findings suggest that substrate may reduce pesticides on biological control agents that burrow, making them more effective.     

Dividing the pie: differential dung pat size utilization by sympatric Haematobia irritans and Musca autumnalis

Horn flies [Haematobia irritans (Diptera: Muscidae) (L.)] and face flies [Musca autumnalis (Diptera: Muscidae) De Geer] use the same larval resource, but their interactions are poorly studied. Dung pats (n = 350) were core sampled in the summers of 2012 and 2013 from irrigated pastures in Pomona, California, U.S.A. (34°03′N, 117°48′W) and held for face fly and horn fly emergence. Surface areas and estimated weights were recorded for each whole pat. Almost half (42.0%) of the pat cores yielded neither fly, 29.7% yielded horn flies only, 12.9% yielded face flies only and 15.4% yielded both flies. Of the fly‐positive pats, surface area and mass were larger for face fly‐occupied pats, whereas horn fly‐occupied pats were smaller. Pats shared by the two species were intermediate. Horn flies per positive core were unaffected by the absence/presence of face flies, but half as many face flies emerged when pats were co‐inhabited by horn flies. Face flies inhabited larger pats, which might better resist heating and drying, to which they are susceptible; horn flies inhabited a broad pat size range. Horn fly tolerance of lower dung moisture probably allows horn flies to colonize and survive in a wide range of pats in dry areas like southern California.     

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.     

Infectivity of two members of theEntomophthora muscae complex [Zygomycetes: Entomophthorales] forMusca domestica [Dipt.: Muscidae]

Dose-mortality studies were conducted with 2 members of theEntomophthora muscae (Cohn) Fresenius complex from southern California (CA) and Denmark (DA) infecting house flies,Musca domestica L., from southern California. Primary conidia of the DA form were significantly more infective (LC₅₀=34 conidia/mm²) than primary conidia of the CA form (LC₅₀=67 conidia/mm²) for 2–7 days old (‘young’) flies. Infectivity (single experimental trial) for 10–14 day old (‘old’) flies of primary conidia of the CA form (LC₅₀=34 conidia/mm²) was similar to that of the DA form for young flies. Secondary conidia of the CA form were markedly more infective (LC₅₀=0.36 conidia/mm²) than primary conidia of either form. Dose had no significant effect on incubation period for primary conidia of either form, but increased doses resulted in significantly shorter incubation periods for flies exposed to secondary conidia of the CA form.      

Behavioural responses of stable flies to cattle manure slurry associated odourants

Stable flies (Stomoxys calcitrans [Diptera: Muscidae] L.) are blood‐feeding synanthropic pests, which cause significant economic losses in livestock. Stable fly antennae contain olfactory sensilla responsive to host and host environment‐associated odours. Field observation indicated that the abundance of stable flies increased significantly in grasslands or crop fields when cattle manure slurry was applied. Major volatile compounds emanating from manure slurry were collected and identified. Behavioural responses of stable flies to those compounds were investigated in laboratory bioassays and field‐trapping studies. Results from olfactometer assays revealed that phenol, p‐cresol and m‐cresol were attractive to adult stable flies. When tested individually, attraction was higher with lower dosages. Stable flies were most attracted to blends of phenol and m‐cresol or p‐cresol. Traps with binary blend lures caught more stable flies in field trials as well.     

Toxicity of baited spinosad formulations to Ceratitis capitata: from the laboratory to the application

GF‐120, a fruit fly bait designed to attract and kill adult fruit flies, was tested in the laboratory and outdoors to determine effects of pre‐treatment diet and bait aging on mortality of Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Two spinosad‐based compounds, GF‐120 and Tracer^® Ultra, had generated two distinctive dose–mortality responds, with LC⁸⁰, LC⁹⁰, and LC⁹⁹ values of 2.4, 2.8, and 4.1 p.p.m., and 255, 479, and 1 143 p.p.m., respectively. The residues of GF‐120 drops, after feeding to the flies, generated 14.3% mortality. The droplet size of the baited spray plays an important role. The toxicity of large drops lasted more than that of small droplets. In the field, exposure to the sun further deteriorates the compound, which lost 50% of its toxicity within 6 days. Disappearance of the compound in the field, due to consumption by various insects, also played a role as 50% of the GF‐120 drops disappeared within 7 days. As mortality was directly related to the amount of insecticide eaten, the effect of GF‐120 depended on the feeding status of the flies: well‐fed flies were almost unaffected compared with starved ones.     

Wolbachia in wasps parasitic on filth flies with emphasis on Spalangia cameroni

The house fly, Musca domestica L., and the stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), are cosmopolitan pests parasitized by a guild of more than two dozen species of wasps. Several species of these wasps have been commercialized as biocontrol agents or are being studied for this purpose. Wolbachia bacteria are known to infect at least some of these wasps and are of interest because infections can dramatically affect insect reproduction. A survey in this parasitoid–fly system detected Wolbachia in 15 of 21 species of wasps and in three of nine species of flies parasitized by these wasps. Phylogenetic analyses using wsp gene sequences identified single isolate infections in most cases. Infections of two and four isolates were detected in Nasonia vitripennis (Walker) and Spalangia cameroni Perkins (Hymenoptera: Pteromalidae), respectively. Laboratory experiments showed infections in S. cameroni to cause an incomplete form of female‐mortality (FM) type cytoplasmic incompatibility (CI). Crosses between uninfected female and infected male partners (♀×♂^w) produced fewer progeny, which had a strong male‐biased sex ratio. Crosses between ♀×♂, ♀^w×♂^w, and ♀^w×♂ produced more progeny, which had a female‐biased sex ratio. Developmental times of progeny were increased when the paternal parent was infected with Wolbachia, regardless of whether the maternal parent was infected or whether offspring developed from fertilized eggs. This result may reflect the action of Wolbachia on components of the seminal fluid that then affect the development of offspring from inseminated females. It is hoped that future studies of Wolbachia in this guild will facilitate the rearing and application of these wasps as biocontrol agents of house fly and stable fly.     

Pasture dragging fails to reliably suppress the emergence of horn flies (Haematobia irritans) and face flies (Musca autumnalis) from dung pats in a Mid-Atlantic North American climate

The beef industry endures major economic losses from a complex of flies that feed on bovine blood and mucus. For cattle on pasture, the most important of these pests are horn flies (Haematobia irritans [L.] [Diptera: Muscidae]) and face flies (Musca autumnalis [Diptera: Muscidae] De Geer). Pasture dragging to spread manure pats has been promoted as a management tactic for these species because their larvae inhabit bovine manure pats, but the efficacy of this practice has not been empirically validated. Spreading pats might promote fly mortality through desiccation or overheating, but these processes are weather-dependent and warrant testing in disparate climates. We evaluated pasture dragging effects while monitoring for weather interactions throughout nine experiment rounds in summers of 2018 and 2020 in Pennsylvania, USA. The manure spreading treatments increased pat surface area up to 300% but failed to significantly reduce emergence of horn flies and face flies as compared to controls. In contrast, precipitation and temperature were significant predictors in fly emergence models. Surprisingly, face fly emergence was significantly elevated in dragged pats twice in 2020. These data call for a reevaluation of pasture dragging as a management technique for horn flies and face flies across a range of climates.     

Highly Toxic and Broad-Spectrum Insecticidal Bacillus thuringiensis Engineered by Using the Transposon Tn917 and Protoplast Fusion

The chromosome of the Bacillus thuringiensis strain S184 that was toxic against the third instar larvae of Spodoptera litura with the LC₅₀ of 9.74 μg/ml was successfully integrated into two genes of cyt1Aa and cry11Aa using the transposon Tn917, yielding the primary engineered strain TnX. The strain TnX was highly toxic to the third instar larvae of Culex pipiens fatigans with the LC₅₀ of 5.12 ng/ml which was 1.82-fold higher than that of B. thuringiensis subsp. israelensis, but lowly toxic to lepidopterous larvae. By the protoplast fusion of the strain TnX and the strain S184-Tet^r (resistance to tetracycline), the target engineered strain TnY was obtained. Against the third instar larvae of S. litura, the strain TnY LC₅₀ was of 4.68 μ g/ml and increased by 2.08-fold in comparison with the parent strain S184. Against the third instar larvae of C. pipiens fatigans, the strain TnY LC₅₀ was of 103.20 ng/ml. The two target genes of cyt1Aa and cry11Aa integrated into the chromosome were extremely stable and had little possibility of a second transposition. It was unclear whether some factors existing in the parent strain, S184, contributed to the high toxicity of the strains TnX and TnY. Received: 30 November 2000 / Accepted: 10 January 2001