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Mosquitoes utilize a plethora of digestive enzymes to meet the challenge of both requisite blood and sugar meals that enable them to survive and reproduce. Sugar meals, typically derived from plant sources, are critical to maintain energy in both male and female mosquitoes, whereas blood meals are taken only by females to complete oogenesis. Enzymes involved in sugar digestion have been the subject of study for decades but have been limited to a relatively narrow range of mosquito species. The southern house mosquito,Culex quinquefasciatus, is of public health importance and seldom considered in these types of studies outside of topics related toBacillus sphaericus, a biocontrol agent that requires interaction with a specific gut-associated α-glucosidase. Here we sought to describe the nature of α-glucosidases and the unexplored β-glucosidases that may aidCx. quinquefasciatuslarvae in acquiring nutrients from cellulosic sources in their aquatic environments. Consistent with our hypothesis, we found both α- and β-glucosidase activity in larvae. Interestingly, β-glucosidase activity all but disappeared at the pupal stage and remained low in adults, while α-glucosidase activity remained in the pupal stage and then exceeded larval activity by approximately 1.5-fold. Expression of the putative α- and β-glucosidase genes chosen did not generally follow the trends seen in enzyme activities. When the α-glucosidase inhibitor acarbose was administered to adults, mortality was seen especially in males but also in females after two days of exposure and key energetic storage molecules, glycogen and lipids, were significantly lower than controls. In contrast, administering the β-glucosidase inhibitor conduritol β-epoxide to larvae did not produce mortality even at the highest soluble concentration. Here we provide insights into the importance of α- and β-glucosidases on the survival ofCx. quinquefasciatusin their three mobile life stages.

With widespread resistance to a limited number of insecticides available for medical and veterinary pests, new insecticides and insecticide synergists are desperately needed in this market space. We assessed the topical toxicity of carvone, menthone, and fenchone compared to permethrin and methomyl against the yellow fever mosquito, Aedes aegypti, and the house fly, Musca domestica. We also evaluated the synergistic potential of the monoterpenoids with permethrin and methomyl. Additionally, we assessed the acetylcholinesterase inhibitory potential of each monoterpenoid compared to methomyl. While all three monoterpenoids performed relatively poorly as topical insecticides (LD50 > 4000 ng/mg on M. domestica; > 6000 ng/mg on Ae. aegypti), they synergized both permethrin and methomyl as well as or better than piperonyl butoxide (PBO). Carvone and menthone yielded synergistic co-toxicity factors (23 and 29, respectively), which were each higher than PBO at 24 h. Acetylcholinesterase inhibition did not appear to explain the toxic or synergistic effects of the three monoterpenoids with IC50 values greater than 1 mM for all, compared to the 2.5 and 1.7 µM for methomyl on Aedes aegypti and Musca domestica, respectively. This study provides valuable monoterpenoid toxicity and synergism data on two pestiferous insects and highlights potential for these chemistries in future pest control formulations.

Most parasitoid wasps parasitize herbivorous insects, so nectar from flowers is readily available. However, parasitoid wasps are also an important component of the rich invertebrate communities at livestock facilities in large accumulations of manure, where flowers are largely absent. Little is known about adult parasitoid diet and nutrition in these communities. The present study examined this in Spalangia cameroni Perkins, a pupal parasitoid of filth flies. Like many parasitoid wasps, S. cameroni feed on host fluids, and in the laboratory readily feed on honey or a sucrose solution, which increases their longevity. Here adult longevity in the presence of six potential food sources, bovine manure, sorghum silage, bovine milk, buckwheat inflorescence (Polygonaceae), sweet alyssum inflorescence (Brassicaceae), or dandelion inflorescence (Asteraceae), was compared to that with water or honey. Only parasitoids given buckwheat lived as long as parasitoids given honey, and parasitoids given honey or buckwheat lived longer than parasitoids given water. Parasitoids readily ate buckwheat nectar, avoiding pollen grains. Diet affected the amount of free sugars, glycogen, and lipids in complex ways. Compared to parasitoids that were given just water, parasitoids with access to honey or sucrose had higher sugar and glycogen levels, but not detectably higher lipid levels. Access to buckwheat had no detectable effect on a parasitoid’s free sugar, glycogen, or lipid levels; however, then after 4 d with just water, sugar levels were lower and glycogen levels were higher compared to parasitoids that had been given access to only water the entire time.

Culex pipiens complex is an important vector of epizootic and zoonotic pathogens, including West Nile virus. Chicago, Illinois and its suburbs have suffered high incidence of human West Nile virus infections in the past. This makes abatement programs in and around the Chicago area an essential service. The control of Cx. pipiens is often complicated by rapidly evolving resistance to pyrethroids, which are the most widely used chemical class in US mosquito abatement programs. The present study assessed Sumithrin® resistance in Cx. pipiens collected from five locations around Cook County, Illinois, neighboring the city limits of Chicago. According to CDC guidelines, samples from all five locations demonstrated some resistance to Sumithrin®. When assessed with Anvil®, a formulated product made of Sumithrin® synergized with piperonyl butoxide, susceptibility was rescued in mosquitoes from three out of the five locations, suggesting involvement of mixed-function oxidases and/or carboxylesterases in Sumithrin® resistance at these locations. Not all locations had susceptibility rescued by Anvil®, but these locations had relatively low knockdown resistance allele frequencies, suggesting that mechanisms other than knockdown resistance may be involved. Enzyme activities did not reveal any marked trends that could be related back to mortality in the bottle bioassays, which highlights the need for multiple types of assays to infer enzymatic involvement in resistance. Future directions in pyrethroid resistance management in Chicago area Cx. pipiens are discussed.

Muscid flies, especially house flies (Musca domestica L.) (Diptera: Muscidae), are a major pest of poultry layer facilities. Augmentative biological control of muscid flies with pteromalid wasps has gained increased attention in recent years. Knowing which pteromalid species are present in a specific area could produce more effective filth fly control. The purpose of this project was to survey parasitoid populations in poultry layer facilities in central and southeastern Pennsylvania from June through September. Two genera of parasitoids, Spalangia and Trichomalopsis, were collected over the course of the survey. Overall, out of 3,724 parasitized pupae the species collected in order of most to least common were Spalangia cameroni Perkins, Spalangia nigroaenea Curtis, Trichomalopsis spp., and Spalangia endius Walker. House fly parasitism overall and by each parasitoid species varied by location and over the four study months. A second objective was to evaluate a new parasitoid trap for surveying parasitoid wasp populations. This device uses a combination of house fly third instars and development media. This was compared to a more traditional method, the sentinel bag, which uses only fly pupae. A higher proportion of Spalangia spp. emerged from the new trap design and more Trichomalopsis spp. emerged from the sentinel bag. This suggests that using this new device alongside the traditional collection method may result in more accurate sampling of pteromalid populations.

The house fly, Musca domestica L. (Diptera: Muscidae), is a global pest of humans and animals that carries scores of pathogens and costs up to $1 billion per year in the United States alone. Information is reviewed on recognition, distribution, biology, dispersal, and associations with microbes. Particular challenges of managing flies in different animal systems are discussed for swine, poultry, dairy cattle, beef feedlot, and equine operations. Effective fly management requires diligent monitoring and integration of cultural control, especially manure management, with mechanical control, traps, conservation or augmentative biological control, and judicious use of insecticides. House fly is notorious for developing insecticide resistance and its resistance status is summarized as of August 2020. Several critical research needs are identified. Monitoring systems and nuisance/action thresholds need improvement. Faster-killing strains and better formulations are needed to integrate pathogens into Integrated Pest management (IPM) programs. The use of parasitoids remains an inexact science with many questions remaining about species selection and release rates. New attractants are needed for use in traps and attract-and-infect/kill strategies. Screening of new active ingredients for toxicity should continue, including a rigorous assessment of essential oils and other botanicals. Rising global temperatures may affect the balance of the fly with natural enemies. An understanding of the fly microbiome may reveal unknown vulnerabilities, and much remains to be learned about how flies acquire, retain, and transmit human and animal pathogens. System-specific research is also needed to tailor fly IPM programs to individual animal systems, especially in organic and free-range animal production.

Veterinary and medical entomologists who are involved in research on pest control often need to perform dose–response bioassays and analyze the results. This article is meant as a beginner’s guide for doing this and includes instructions for using the free program R for the analyses. The bioassays and analyses are described using previously unpublished data from bioassays on house flies, Musca domestica Linnaeus (Diptera: Muscidae), but can be used on a wide range of pest species. Flies were exposed topically to beta-cyfluthrin, a pyrethroid, or exposed to spinosad or spinetoram in sugar to encourage consumption. LD50 values for beta-cyfluthrin in a susceptible strain were similar regardless of whether mortality was assessed at 24 or 48 h, consistent with it being a relatively quick-acting insecticide. Based on LC50 values, spinetoram was about twice as toxic as spinosad in a susceptible strain, suggesting a benefit to formulating spinetoram for house fly control, although spinetoram was no more toxic than spinosad for a pyrethroid-resistant strain. Results were consistent with previous reports of spinosad exhibiting little cross-resistance. For both spinosad and spinetoram, LC50 values were not greatly different between the pyrethroid-resistant strain and the susceptible strain.

Filth flies cause billions of dollars of losses annually to the animal production industry. Fluralaner is a relatively new pesticide currently sold for control of fleas, ticks, and mites on companion animals and poultry. We examined the efficacy of fluralaner against three species of filth flies. Insecticide-susceptible horn flies and stable flies were tested topically. Fluralaner outperformed permethrin by > 2-fold for the horn flies but underperformed permethrin by > 45-fold for stable flies at 24 h. House flies were tested topically with fluralaner in comparison to permethrin at 48 h and orally with fluralaner in comparison to imidacloprid at 24 h. Topical fluralaner was 6- to 28-fold as toxic as permethrin in four pyrethroid-resistant strains and not significantly less toxic than permethrin in a susceptible strain and a mildly pyrethroid-resistant strain. There was slight cross-resistance between topically applied fluralaner and permethrin in all five insecticide-resistant strains tested. Oral fluralaner was more toxic than imidacloprid in all four house fly strains tested, 9- to 118-fold as toxic. Oral cross-resistance between imidacloprid and fluralaner was not detected, but imidacloprid resistance was not high in any of the tested strains. Fluralaner shows promise for control of horn flies and house flies.

Concentrated swine production can produce large amounts of accumulated waste that may serve as development sites for pest flies. Filth flies are not only a nuisance but can also interfere with animal growth and production and are capable of mechanically transmitting many pathogens to swine on confinement facilities. In addition to production and health concerns, high populations of filth flies developing on concentrated animal facilities may subject producers to nuisance litigation. While litigation against livestock producers associated with pest filth flies has become more frequent and high profile, information on the filth fly fauna in swine facilities in the United States is limited. In this study, filth fly species diversity and population fluctuations were monitored with spot and sticky cards in one sow facility and two finishing facilities in North Carolina. House flies Musca domestica L. (Diptera: Muscidae) were the dominant species followed by black dump flies Hydrotea (Ophyra) aenescens Weidemann (Diptera: Muscidae). A difference was seen in total spots on cards placed in more central barn locations than towards the outer walls in the sow facility but not the finishing facilities. Mean spots at only one of the finishing facilities exceeded the conventional control threshold of 100 spots/week, in May and June. Fly numbers decreased naturally in the following months, suggesting that standard control thresholds may not accurately inform filth fly control efforts in swine production. Due to their complementary nature, both spot and sticky cards placed in representative locations throughout barns are recommended. However, more swine-specific information is needed for optimizing monitoring methods.

Filth flies, including house flies, Musca domestica L., develop in animal manure. Adult house flies often are controlled with pesticides such as imidacloprid. How imidacloprid disseminates and persists after it contaminates manure was measured at a dairy farm. A week after application of imidacloprid via fly bait to cattle manure, a mean of approximately 4 ppm of imidacloprid, and as high as 15 ppm, was quantifiable up to 12 cm from the application site, but not farther. Laboratory experiments addressed the impact of 15 ppm of imidacloprid in manure on egg-to-adult development of house flies and on the biological control ability of a house fly pupal parasitoid, Spalangia endius Walker. In uncontaminated manure, 93% of eggs developed to adults, versus 7% in contaminated manure. In the parasitoid experiment, fly pupae were placed in contaminated or uncontaminated manure with or without S. endius. In the absence of S. endius, nearly 100% of flies emerged, with or without imidacloprid. In the presence of S. endius, only 11% of flies emerged from uncontaminated manure, versus 36% from contaminated manure; and parasitoids emerged from 82% of hosts in uncontaminated manure versus 53% in contaminated manure. These results suggest that realistic concentrations of imidacloprid in filth fly breeding habitat may interfere with house flies developing to the pupal stage, but also with parasitoids locating and utilizing house flies. However, after 1 wk, the effects on parasitoids will be low 12 cm beyond where bait was applied.

Pest management plans for house flies, Musca domestica L. (Diptera: Muscidae), often include insecticides. Because of resistance and environmental concerns with traditional insecticides, safe new pesticides and pesticide formulations are needed. The insecticidal potential of two sugar alcohols, xylitol and erythritol, against adult house flies was assessed. Flies consumed both xylitol and erythritol. The proportion of flies that exhibited the proboscis extension reflex, which is associated with feeding, did not differ significantly between the sugar alcohols and sucrose in an experiment with 20% solutions and older flies, but was less for the sugar alcohols in an experiment with 2M solutions and younger flies. When presented alone or mixed with sucrose, both sugar alcohols significantly decreased fly survival relative to just sucrose. There was a strong negative relationship with concentration and mean days survived for xylitol, but no significant relationship for erythritol or sucrose. Relative to sucrose alone, a temporary exposure to xylitol, but not to erythritol, decreased survival when sucrose was subsequently available. Although xylitol and erythritol can both decrease survival of house flies and would meet the criteria for organic farming, deaths were often not very immediate. However, continued investigation of a variety of sweeteners as feeding-stimulant alternatives to sucrose is still useful, to minimize the risk of house flies evolving resistance to the sugar in baits. Our analysis of already published data on house flies that had been repeatedly exposed to a sucrose-based bait is consistent with the evolution of sucrose-feeding avoidance.

Foreign materials like insecticides may increase grooming in insects; and generally, grooming may be expected to reduce effects of insecticides, but this may not be the case when grooming involves the mouth and hence a risk of ingestion. To examine this, female Spalangia endius, a wasp that parasitizes filth fly pupae, were exposed to a surface coated with a low concentration of imidacloprid or not. Their mouthparts were sealed or not to determine whether sealing is a useful method for examining effects of mouth grooming. Wasps mouth-groomed more frequently while exposed to imidacloprid than when not. However, imidacloprid did not increase the number of times that a wasp groomed the rest of her body, and this was true regardless of whether or not her mouthparts were sealed. While exposed to imidacloprid, wasps spent less time locomoting only if their mouthparts were not sealed. Having been exposed to imidacloprid also decreased subsequent longevity, from 9 to 7 d. These effects of imidacloprid on grooming, locomotion, and longevity occurred despite exposure being for just 5 min and to only 2% of the amount that will be present in an area immediately after house fly baits are scattered at their recommended coverage. This is such a low amount that, with 48 h of constant exposure, mortality of these wasps is only 10%. Having mouthparts sealed decreased locomotion and longevity regardless of exposure to imidacloprid. Thus, sealing mouthparts is not useful for measuring effects of mouth grooming.

Use of insecticidal baits risks the evolution of resistance to the feeding stimulant in the bait, not just to the active ingredient (toxicant). Sucrose-based baits are widely used against house flies, Musca domestica L. The baits are applied as dry granules, but readily liquefy. The proboscis extension reflex (PER) and consumption of alternative sweeteners, dry or in solution, were examined. Fructose, glucose, and xylitol merit further study as alternatives to sucrose. Dry, fructose, glucose, and xylitol elicited PER much more than sucrose, although not when in solution. Furthermore, dry or in solution, females and males ate as much or more fructose as sucrose. In solution, flies ate as much glucose as sucrose; although when dry, consumption was much less for glucose than sucrose. Dry, xylitol elicited as much consumption as sucrose for females, though less for males. In solution, for both sexes, xylitol elicited less consumption than sucrose did. Acesulfame potassium, sodium cyclamate, and sucralose do not look promising as they did not often elicit PER, whether dry or in solution. Erythritol also does not look promising. Erythritol elicited PER no more than sucrose did when dry and elicited PER much less than sucrose when in solution. Flies ate much less erythritol than sucrose whether dry or in solution.

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.

Behaviors and mortality of two filth fly parasitoid wasps, Spalangia endius Walker and Urolepis rufipes Ashmead, were tested in response to granular fly baits containing one of the three active ingredients (AI): Golden Malrin (methomyl), QuickBayt (imidacloprid), or Quikstrike (dinotefuran). Behavioral responses to each of the two components of the baits, the AIs and the fly attractant pheromone (Z)-9-tricosene, were also examined independently. Spalangia endius avoided contact with bait granules, regardless of bait type. However, when S. endius contacted bait residue, the imidacloprid bait appeared to be the least harmful of the baits for S. endius, at least in the short term. Spalangia endius was attracted to imidacloprid by itself. However, S. endius avoided (Z)-9-tricosene. In contrast to S. endius' attraction to imidacloprid, S. endius neither avoided nor was attracted to methomyl or dinotefuran. For U. rufipes, the methomyl bait appeared to be especially harmful. Urolepis rufipes avoided bait granules with imidacloprid or dinotefuran but not with methomyl, died quickly in the presence of methomyl bait residue, and had a methomyl LC50 that was lower than that for S. endius The avoidance by U. rufipes of granules with imidacloprid or dinotefuran appears to be related to components other than the AIs or the (Z)-9-tricosene because U. rufipes did not avoid either individually. The behavioral avoidance of the parasitoids in the present study occurred despite no exposure recently, if ever, to these pesticides.

The house fly, Musca domestica (L.) (Diptera: Muscidae), and the stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), are two filth flies responsible for significant economic losses in animal production. Although some chemical control products target adults of both species, differences in mouthpart morphology and behavior necessitates distinct modalities for each. For these reasons, larvicides are an attractive means of chemical control. We assessed the potential of the polyol sweeteners erythritol and xylitol as larvicides to the house fly and stable fly. LC50 values of erythritol against 2nd instar larvae were 34.94 mg/g media (house fly) and 22.10 mg/g media (stable fly). For xylitol, LC50 values were 74.91 mg/g media (house fly) and 41.58 mg/g media (stable fly). When given a choice, neither species showed a preference for ovipositing in media treated with either sweetener at various concentrations or in media without sweetener. Significantly lower development from egg to adult was observed when the 2nd instar LC50 equivalent of each sweetener was present in the media compared to controls. Erythritol and xylitol both have larvicidal qualities, however their effective concentrations would necessitate creative product formulation and deployment methods to control all stages of developing flies.

The parasitoid wasps Spalangia endius Walker, Spalangia nigroaenea Curtis, and Spalangia nigra Latrielle (Hymenoptera: Pteromalidae) develop on filth fly pupae. Females burrow through decaying organic matter and parasitize hosts; whereas, at least in S. endius, males tend to stay above ground searching for mates. Both sexes lack obvious digging morphology such as enlarged forelegs and are not known to exhibit physical aggression. Size data were obtained from specimens from Illinois field-collected hosts for all three species and from a Florida laboratory colony for S. endius. The degree of sexual size dimorphism varied with body part and species, but the direction of bias was consistent between the field and laboratory specimens of S. endius. Females had wider abdomens in S. nigroaenea and S. nigra (not measured in S. endius). In all three species, females had longer heads than males, both in absolute size and relative to width. The latter is referred to as narrowness. Forewings were significantly narrower in females compared with in males for both S. endius and S. nigroaenea. Thorax narrowness was either greater in males (S. endius) or was not significantly different between the sexes (S. nigroaenea and S. nigra). Patterns of sexual size dimorphism seem consistent with females’ need to store eggs and burrow. For all three species, there was overlap between males and females in all body parts measured. Thus, these size measurements will be unreliable to differentiate the sexes. Size ratios also overlapped.

Documented resistance to traditional insecticides in the house fly, Musca domestica L. (Diptera: Muscidae), has expedited a need for alternative forms of control. One such method is the use of biological control organisms, such as the entomopathogenic fungus, Beauveria bassiana (Balsamo - Crivelli) Vuillemin (Hypocreales: Clavicipitaceae). Administering B. bassiana with a calorically rich phagostimulant such as sucrose may have the unintended effect of increasing fly vitality and thus reproduction before mortality sets in. Therefore, finding a phagostimulant with lower caloric value that can replace sucrose is valuable. Here B. bassiana was combined with the sweeteners erythritol and xylitol as potential low-calorie substitutes for sucrose. Female flies consumed as much xylitol alone as they did sucrose alone, but less erythritol than both. After 24 h of exposure, B. bassiana administered at 1 mg in erythritol and in sucrose were equally effective at reducing survival and better than xylitol. B. bassiana administered at 10 mg worked equally well at reducing survival in all three sweeteners. When exposed to 10 mg of B. bassiana in sweetener for 1 h, sucrose reduced survival more than in erythritol or xylitol, but mortality was still in excess of 97% after 8 d in all three sweeteners. Each sweetener mixed with B. bassiana worked as well in an environment with additional food sources and stimuli as they did in an environment lacking these additions. Erythritol and xylitol appear to be strong candidates to replace sucrose in baits formulated around B. bassiana.

Various insecticides for the control of the house fly Musca domestica L. were tested for compatibility with a biological control agent, the pupal parasitoid Spalangia endius Walker. Bioassays used the mode in which each organism was expected to be harmed by the insecticides, a surface contact bioassay for S. endius and a feeding bioassay for M. domestica. A Pesticide Compatibility Index (PCI) was created that allows comparison of LC50 values when the mode of exposure to a pesticide differs. First LC50 values were converted into units of prescribed dosages (LPR=LC50-to-prescribed dosage ratio). This study used dosages from labels of granular baits. PCI is the ratio of LPRbiological control agent to LPRpest. For these PCI values, order of compatibility with S. endius was spinosad>thiamethoxam>inotefuran>methomyl>imidacloprid. That spinosad was better than imidacloprid or methomyl, both for parasitoid survival and for killing flies, is consistent with conclusions from the LC50 values. Permethrin and nitenpyram were also tested, but their PCIs were not calculated. Permethrin is prescribed as a contact insecticide against flies rather than being consumed as a bait, and nitenpyram has not been formulated as a fly insecticide. Compared with the other insecticides in terms of LC50 values, permethrin was moderately toxic to S. endius but one of the most toxic for M. domestica, whereas nitenpyram was least toxic for both S. endius and the flies.