Search

House flies, (Musca domestica L.) and stable flies (Stomoxys calcitrans L.) are common pests on equine facilities. Biological control of these flies with pupal parasitoids has become increasingly popular with horse owners but has not been evaluated on equine facilities. Little is known of the substrate preferences of filth fly parasitoids on equine facilities, but the success of release programs may be affected by microhabitat preferences. Spalangia cameroni Perkins was evaluated for location preferences for parasitization of house fly and stable fly puparia in six substrates commonly found on equine farms in Florida. Substrates were evaluated at 20:1 and 5:1 H:P ratios and during the experiment parasitoids had access to all substrates simultaneously. No differences were observed between filth fly host species in any of the measured parameters: total host mortality, parasitoid progeny production and residual host mortality. Significant effects of H:P ratio on host mortality and residual mortality were found but not on progeny production. While there were significantly more hosts killed in the aged shavings than the fresh shavings at the 20:1 ratio, no differences were observed at the 5:1 ratio. Additionally, no differences were found in progeny production across substrates at the 20:1 ratio, but higher reproductive success was observed in several substrates at the 5:1 ratio. These results demonstrate that S. cameroni had substrate preferences but that these preferences were absent with reduced host density. This parasitoid species appears to be effective at parasitizing hosts in the common equine substrates of Florida. more...

Muscididfurax raptor , a pupal parasitoid of house flies and other filth flies, is commonly infected with the microsporidium Nosema muscidifuracis . To determine the effects of infection on developmental time, uninfected and infected adult M. raptor were allowed to parasitize pupae of the house fly ( Musca domestica ) for 24 h. Exposed pupae of the two groups (infected and uninfected) were held at 15, 20, 25, 30, 32, and 34 °C with 75–80% relative humidity. Development of infected M. raptor was significantly longer at all temperatures than that of uninfected parasitoids, resulting in approximately 7% extensions of developmental times. Uninfected females completed development in 14.6, 19.6, and 30.4 days at 30, 25, and 20 °C, respectively, compared with 15.8, 20.7, and 32.3 days for infected females at these temperatures. The differences in developmental times provided narrow windows for isolating large proportions of uninfected M. raptor females for disease management programs. This window was greatest at 20 °C; 61% of the uninfected females emerged by day 30, at which time only 10% of the infected females had emerged. more...

Parasitoids are often members of species complexes and are difficult to identify by conventional morphology, although most indigenous parasitoids of muscoid flies can be identified from adults. Pupal exuviae of the gregarious parasitoids Muscidifurax raptorellus Kogan and Legner and Nasonia vitripennis (Walker) were dissected from parasitized house fly (Musca domestica L.) puparia. Their hydrocarbons were extracted, isolated, and analyzed via column and gas chromatography, as were those of adult parasitoids. Quantification of 7-methylhentriacontane and 3,7,15-trimethylpentatriacontane allowed calculation of peak ratios of these two methyl-branched components that showed statistically significant differences between the species. Since the profiles were dramatically different, a confident identification resulted. Analysis of adult parasitoids or the mummified host remains from parasitized host puparia also revealed distinctive hydrocarbon profiles between species, and the same peak ratios were definitive for each species. Since there are no morphological keys for pupal life stages, hydrocarbon profiles provide a simple and reliable method to identify parasitoids from parasitized host puparia, before or after the adult parasitoids have left the host. In addition, the parasitoid species found in parasitized pupae can be determined from analysis of the empty puparium or even the mummy itself. more...

In forced-contact bioassays in which hosts were vortexed for 5 s in 5 ml of fungal inoculum, young larvae of the lesser mealworm (Alphitobius diaperinus) were highly susceptible to a strain of the fungal pathogenBeauveria bassiana(WV) that was isolated from a natural epizootic inA. diaperinus(5-day-old larvae LC50 = 1.73 × 102conidia/ml, LC90 = 9.86 × 103; 10-day-old larvae LC50= 2.49 × 102, LC90 = 4.74 × 104). Adult beetles were approximately 1000 times less susceptible than young larvae. Mature larvae and adult beetles were more susceptible to WV and to a second beetle-derived strain (NC) than they were to two strains that originated in house flies. Starch dust formulations were more effective than aqueous suspensions when conidia were applied to poultry litter containing manure, chicken feed, and pine shavings. Because the experiments were conducted a single time, small differences among strains, formulations, and life stages should be viewed with caution. Soil treatments with corn starch containing the WV and NC strains provided 100% control of beetle larvae at 2.5 × 1011conidia/m2; aqueous suspensions were less effective. A pupal trap consisting of conidia-treated cardboard provided 100% control of beetle larvae at 4 × 105conidia/cm2of trap surface. An estimated 3 × 1011conidia could be used to treat a 1200-m2poultry house with the pupal traps. more...

Gas chromatographic analysis of cuticular hydrocarbons ofMuscidifuraxspp. adult females revealed species-specific patterns of composition that allowed identification ofMuscidifurax raptorGirault and Sanders,Muscidifurax zaraptorKogan and Legner, andMuscidifurax raptorellusKogan and Legner. A total of 18 components, all C29–C37 alkanes and methylalkanes, accounted for over 90% of the total cuticular hydrocarbons for all three species.Muscidifurax zaraptorwas characterized by a high ratio (11.9) of 3-MeC31:internal Me2C35's, whereas this ratio was more...

When housefly eggs were exposed toParaiotonchium muscadomesticaeColer and Nguyen from nematode-infected flies, an IC50(concentration resulting in 50% of the hosts becoming infected) of 23.7 gamogenetic nematodes/fly egg was observed, with an IC90of 183.8. Mortality was low except at high nematode concentrations (LC50 = 4901, LC90 = 102,517). Infected adult flies of both sexes lived about half as long as uninfected flies. Examination of nematode age structure in infected flies revealed that mature gamogenetic females produced about 8 parthenogenetic females each regardless of nematode crowding levels. In contrast, production of new gamogenetic nematodes by parthenogenetic females was density-dependent, with average reproductive rates ranging from 1627 progeny/parthenogenetic female at 8 females/host to 330 progeny at 83 females/host. Infected flies contained 12,000–45,000 new gamogenetic nematodes 10–14 days after fly emergence. The percentage of male flies infected with the nematode was equal to the percentage of females infected with the nematode. Gamogenetic nematodes required 24 h after deposition into fly larval rearing medium before they were capable of infecting new host larvae. Nematodes persisted in rearing medium for 3–5 days after deposition; no infections were observed at 7 and 10 days after deposition. more...

Development rates were determined for three pteromalid parasitoids of houseflies under constant and varying temperatures from 15 to 35°C. Muscidifurax raptor Girault and Sanders was the fastest developing species, with females completing development in 13.8 days at 32.5°C and 66.5 days at 15°C. Spalangia gemina Boucek females completed development in 20.8 days at 30.0°C and 161 days at 15.0°C, whereas S. cameroni Perkins females completed development in 20.6 days at 30.0°C and 155.5 days at 15.0°C. Male development times were 90.3% of those for female S. gemina and 92.7 and 88.6% of those for female S. cameroni and M. raptor, respectively. Parasitoid survival was very low at 35°C for all species and no Spalangia survived constant exposure to 15.0°C. Exposure to these lethal temperatures for shorter periods indicated that the parasitoids can tolerate them well under conditions more typical of the field. Development rates were modeled using biophysical and degree-day models and the models were tested for their ability to predict development under fluctuating conditions (24–36°C). Neither model was superior for all three species because of interspecific differences in the parasitoids' responses to high temperatures. Agreement between predicted and observed development times for all three species was achieved by small empirical adjustments of a key parameter in the biophysical model. more...

In assays at constant temperatures, Spalangia gemina Boucek, Spalangia cameroni Perkins, and Muscidifurax raptor Girault and Sanders females killed more house fly ( Musca domestica L.) pupae at 30°C than at 15, 20, 25, or 35°C, with attack rates for the three species of 11.2, 12.6, and 21.1 pupae killed per parasitoid per day, respectively. Progeny production followed a similar pattern, with maximum rates of 6.8, 7.5, and 9.2 progeny per day at 30°C for S. gemina, S. cameroni, and M. raptor, respectively. Both Spalangia species produced proportionally fewer males at higher temperatures than at lower temperatures; sex allocation by M. raptor was relatively unaffected by temperature except for a trend to produce fewer females at 15°C (29.6% females) than at higher temperatures (43–47%). The four-parameter thermodynamic model of Sharpe and DeMichele with high temperature inhibition fit the attack rate and progeny production rate data well. These models were very effective at predicting host attacks and parasitism at high, variable temperatures typical of outdoor mid summer conditions in many regions, provided that 1-h time steps were used in rate summation algorithms. Assays for long-term net rates of fly destruction revealed that S. gemina and S. cameroni would be most effective for fly control at 25°C and substantially less effective at either low (15°C) or high (35°C) temperatures. M. raptor was equally effective at killing house fly pupae over the 15–30°C range, but was significantly less effective at 35°C. more...

The microsporidium Nosema muscidifuracis was found in 1.1 and 10.7% of wild Muscidifurax raptor collected on New York dairy farms in 1991 and 1992. Higher (84%) levels of infection were observed on farms where infected M. raptor from a commercial insectary were released. Adult M. raptor became infected (100%) after feeding on spore suspensions of N. muscidifuracis, whereas house fly (Musca domestica L.) adults and larvae did not. Adult M. raptor became infected (16-25%) after feeding on infected parasitoid immatures within host puparia. Transmission rates of N. muscidifuracis increased with increasing parasitoid crowding levels because of cannibalism by healthy parasitoid immatures on infected immatures in superparasitized hosts. Maternal transmission was 100% efficient but there was no paternal or venereal transmission. Disease was reduced 35-93% by immersing infected parasitoid eggs within fly puparia in a 47°C water bath for 30-60 min. Eliminating disease from an established laboratory colony of M. raptor resulted in a 10-fold increase in parasitoid fecundity. more...

House fly ( Musca domestica L.) populations on six dairy farms in 1988 and four dairy farms in 1989 in New York State were surveyed weekly to determine prevalence rates of Entomophthora muscae (Cohn) Fresenius infections. In addition, E. muscae -infected house flies were produced in the laboratory and placed on dairy farms to induce epizootics on three of the dairy farms in 1988 and two in 1989. Two methods were used to place infected flies on farms: either living, infected flies in cages or infected house fly cadavers in petri dishes were periodically placed in fly aggregation areas in barns. Naturally infected house flies were present on all farms in both years. Prevalence levels on control farms were low prior to 30 August in 1988. In early September prevalence rates began to increase and natural epizootics occurred with prevalence rates of 40-60% in mid-September. A similar pattern was seen in1989 with epizootics in mid- to late September. Prevalence rates were significantly higher on release farms than on control farms in both 1988 and 1989. Overall seasonal prevalence rates were 7.8 and 9.2% in 1988 and 24.6 and 49.3% in 1989 for the control and release farms, respectively. Onset of epizootics on release farms in 1989 was 4-8 weeks earlier than onset in control farms. more...