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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.

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.

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.

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.

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.