Salinity tolerance of stable fly (Diptera: Muscidae)

Effects of salinity on the survival, growth, and development of stable fly, Stomoxys calcitrans (L.), were investigated in the laboratory. Larvae failed to develop to pupation when reared in media containing a salinity of 40 parts per thousand (ppt) sodium chloride (NaCl). Maximum salinity supporting larval development equaled the salinity of seawater (34 ppt); the larval LC90 was 24.2 ppt. Deleterious effects of high salinity decreased as larvae matured. Six-day-old larvae reared at a salinity of 34 ppt weighed 79% less than controls, compared with a 36% difference in 9-d-old larvae; by pupation, the difference was only 24%. Salinity did not influence the duration of larval, pupal, or adult stages. Survival of pupae was unimpaired despite a slight increase in number of pupal deformities, and normal adults emerged. Eggs were highly tolerant to saline. They hatched at salinity concentrations lethal to larvae; greater than 50% hatch occurred even when eggs were maintained at 80 ppt NaCl. Sensitivity of larvae to salinities close to that of seawater might be important for control of stable flies inhabiting marine areas.     

Managing the horn fly (Diptera: Muscidae) using an electric walk-through fly trap

An electric walk-through fly trap was evaluated for the management of the horn fly, Hematobia irritans (L.), on dairy cattle in North Carolina over 2 yr. The trap relies on black lights and electrocution grids to attract and kill flies that are brushed from the cattle passing through. During the first season, horn fly densities were reduced from >1,400 to <200 flies per animal. Horn fly density averaged 269.2 +/- 25.8 on cattle using the walk-through fly trap twice daily, and 400.2 +/- 43.5 on the control group during the first year. The second year, seasonal mean horn fly density was 177.3 +/- 10.8 on cattle using the walk-through fly trap compared with 321.1 +/- 15.8 on the control group. No insecticides were used to control horn flies during this 2-yr study.     

Insecticide resistance and cross-resistance in the house fly (Diptera: Muscidae)

A house fly strain, ALHF, was collected from a poultry farm in Alabama after a control failure with permethrin, and further selected in the laboratory with permethrin for five generations. The level of resistance to permethrin in ALHF was increased rapidly from an initial 260-fold to 1,800-fold after selection. Incomplete suppression of permethrin resistance by piperonyl butoxide (PBO) and S,S,S,-tributylphosphorotrithioate (DEF) reveals that P450 monooxygenase- and hydrolase-mediated detoxication, and one or more additional mechanisms are involved in resistance to permethrin. The ALHF strain showed a great ability to develop resistance or cross-resistance to different insecticides within and outside the pyrethroid group including some relatively new insecticides. Resistance to beta-cypermethrin, cypermethrin, deltamethrin, and propoxur (2,400-4,200-, 10,000-, and > 290-fold, respectively, compared with a susceptible strain, aabys) in ALHF house flies was partially or mostly suppressed by PBO and DEF, indicating that P450 monooxygenases and hydrolases are involved in resistance to these insecticides. Partial reduction in resistance with PBO and DEF implies that multiresistance mechanisms are responsible for resistance. Fifteen- and more than fourfold resistance and cross-resistance to chlorpyrifos and imidacloprid, respectively, were not effected by PBO or DEF, indicating that P450 monooxygenases and hydrolases are not involved in resistance to these two insecticides. Forty-nine-fold cross-resistance to fipronil was mostly suppressed by PBO and DEF, revealing that monooxygenases are a major mechanism of cross-resistance to fipronil. Multiresistance mechanisms in the ALHF house fly strain, however, do not confer cross-resistance to spinosad, a novel insecticide derived from the bacterium Saccharopolyspora spinosa. Thus, we propose that spinosad be used as a potential insecticide against house fly pests, especially resistant flies.     

Effects of horn fly and house fly (Diptera: Muscidae) larvae on the development of parasitic nematodes in bovine dung

Laboratory studies were conducted to determine the effects of horn fly, Haematobia irritans (L.), and house fly, Musca domestica L., larvae on the development of a mixed population of parasitic nematodes in compressed and crumbled bovine dung. Fresh dung (100 g per sample) from a single calf passing trichostrongyle type eggs was infested with 150 horn fly or 150 house fly eggs. After 14-15 d, more horn flies and house flies had emerged from the compressed dung than from the crumbled dung, but more third stage parasitic nematode larvae were recovered from the crumbled dung containing either fly species than from dung containing no flies.     

Parasites that attack stable fly and house fly (Diptera: Muscidae) puparia during the winter on dairies in northwestern Florida

Throughout the winter and early spring months, stable fly, Stomoxys calcitrans (L.), and house fly, Musca domestica L., puparia were collected from silage, hay, and manure from six dairies in northwestern Florida and evaluated for parasitism. Of the puparia producing flies or parasites, 23% of the stable flies and 46% of the house flies were parasitized. The predominant parasite observed attacking muscoid flies (76% for stable flies and 58% for house flies) was Spalangia cameroni Perkins. Muscidifurax sp. was recovered from 11 and 36% of the stable fly and house fly pupae, respectively. Other parasite species encountered were Spalangia endius Walker and S. nigroaenea Curtis. Significantly more parasitized fly pupae were collected from silage than from hay residues or manure. Winter and early spring parasite populations in northwestern Florida appear to be present as long as viable fly pupae are available to support the developing parasites.     

Permethrin metabolism in pyrethroid-resistant adults of the horn fly (Muscidae: Diptera)

The in vivo metabolism of topically applied 14C-permethrin was determined for adults of pyrethroid-resistant and -susceptible horn flies, Haematobia irritans (L.) at 1, 2, and 6 h after treatment. At 1 and 2 h after treatment, resistant horn flies had significantly higher internal levels of radioactivity (permethrin plus metabolites) compared with adults of the susceptible strain. Analysis of the internal extracts by thin-layer chromatography indicated no differences in the levels of permethrin. However, significantly higher levels of metabolites that co-chromatograph with 3-(2'- or 4'-hydroxyphenoxy)benzyl (1RS) cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylate at 1 and 2 h after treatment and (1RS) cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid at 1 h after treatment. These results demonstrate that an enhanced penetration and metabolism are present during the early phases of permethrin intoxication. Enhanced metabolism may contribute to the ability of resistant horn flies to survive in the presence of pyrethroids.     

Muscovy ducks as an adjunct for the control of the house fly (Diptera: Muscidae)

In laboratory trials, Muscovy ducks, Cairina moschata L., removed adult house flies, Musca domestica L., at least 30 times faster than commercial bait cards, coiled fly paper rolls, fly sheets, or fly traps. The LT90 for ducks in 0.24-m3 cages with 100 flies was 0.6 h compared to 15.3 h for the most effective commercial device. Ducks survived for at least 12 wk in pens with calves, without injury or feed supplement. Ducks ingested a mean of 25 house flies per 15-min observation period when populations were low to moderate. The economics and advantages of Muscovy ducks as part of a management program for house fly control are discussed.     

Comparative efficiency of six stable fly (Diptera: Muscidae) traps

Five adhesive traps and the Nzi cloth-target trap were compared to determine their trapping efficiency and biases for stable flies, Stomoxys calcitrans (L.) (Diptera: Muscidae). Two configurations of the BiteFree prototype trap, constructed of polyethylene terephthalate, were most efficient for trapping stable flies, whereas the EZ trap was least efficient. The two Alsynite traps, Broce and Olson, were intermediate to the BiteFree prototype and EZ traps. All adhesive traps collected a ratio of approximately two males for each female. Approximately 50% of the flies collected on the adhesive traps, both male and female, were blood fed, and 20% were vitellogenic. The Nzi trap collected an older component of the stable fly population, 81% blood fed and 62% vitellogenic, but it was much less efficient than the adhesive traps. The effectiveness of the BiteFree prototype trap indicates that materials other than Alsynite are attractive to stable flies.     

Selection for resistance to imidacloprid in the house fly (Diptera: Muscidae)

The house fly, Musca domestica L. (Diptera: Muscidae), continues to be a primary pest of livestock facilities worldwide. This pest also has shown a propensity for pesticide resistance development when under high selection pressures. In this study the house fly strain FDm was created by a 20% contribution from each of five colonies collected from dairies in Florida with known imidacloprid resistance. The FDm strain was used to evaluate the level ofimidacloprid resistance after five selections near the LC70 value of each selected generation. Overall, the mean selection mortality was 72.7, with males being considerably more susceptible than females. The unselected (F0) FDm strain showed considerable susceptibility to imidacloprid after its creation, compared with the five parental strains. Between 9500 and 14,000 virgin house flies were used in each selection. After the fifth and final selection, a 331-fold increase in imidacloprid resistance at the LC70 was observed over the parental FDm strain. In parallel studies, the FDm strain showed increasing tolerance of the commercial imidacloprid product QuickBayt. These results suggest that livestock producers should use caution when choosing pesticides and consider rotating fly baits, as is encouraged with other pesticide treatment regimes on farms.     

Acetylcholinesterase from the horn fly (Diptera: Muscidae) II: Biochemical and molecular properties

Purified acetylcholinesterase (AChE) of the horn fly was characterized to elucidate the enzymological, inhibitory, and molecular properties of the enzyme. Maximum activity of the AChE against the substrate acetylthiocholine (ATCh) occurred when reactions were conducted at 37°C and pH 7.5. Km and V_max values were (9.2 ± 0.35) × 10^?6 M and 239.8 ± 10.8 units/mg, respectively, for ATCh and (1.5 ± 0.07) × 10^?5 M and 138.5 ± 5.5 units/mg, respectively, for butyrylthiocholine (BTCh). The activity of AChE decreased when concentrations of ATCh or BTCh were higher than 1 mM. Studies of the interaction of AChE with different inhibitors revealed pl₅₀ values of 8.88 for eserine, 6.90 for BW284C51, and 4.97 for ethopropazine. Bimolecular reaction constants (k_is) for the organophosphorus (OP) anticholinesterases were (2.74 ± 0.14) × 10⁶ M^?1 min^?1 for coroxon, (7.20 ± 0.28) × 10⁵ M^?1 min^?1 for paraoxon, and (2.33 ± 0.12) × 10⁵ M^?1 min^?1 for stirofos. Two major forms of native AChE molecules were found on non-denaturing polyacrylamide gel electrophoresis (PAGE) with Triton X-100, corresponding to bands AChE-2 and AChE-4 found on PAGE without Triton X-100. AChE-2 had an estimated molecular weight of 603,000 and was amphiphilic. AChE-4 had a molecular weight of 147,000 and was hydrophilic. Results of PAGE analyses indicated that the purified enzyme had two bands, one of about 123 kDa and the other greater than 320 kDa, prior to disulfide reduction and only one band at about 54 kDa after reduction on SDS-PAGE. © 1994 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Microsatellite loci in the house fly,Musca domestica L. (Diptera: Muscidae)

Genomic libraries from house flies enriched for (CA)₁₅ and (CAG)₁₀ repeats were constructed by using biotinylated probes. Twenty‐five loci were isolated and evaluated for polymorphisms in wild flies representing two geographically diverse populations. Fourteen of 19 dinucleotide loci, and one of six trinucleotide loci were polymorphic. One hundred and twenty‐seven alleles were detected, 39 of which were private. Average number of alleles per polymorphic locus was 8.4 ± 2.5 and average heterozygosity was 72 ± 4%. F_ST by the private allele method was 0.73. Three of 15 loci showed significant heterozygote deficiencies, attributed to null alleles. Five of 15 loci were amplified in the face fly, Musca autumnalis.     

Costs of existing and recommended manure management practices for house fly and stable fly (Diptera: Muscidae) control on dairy farms

Costs of fly control practices were estimated for 26 New York and Maryland dairy farms. Objectives were to characterize existing practices, compare them with the cost of more frequent and complete manure removal to reduce fly breeding, and to compare costs of manure removal and insecticide application. Information was collected in scouting visits and personal interviews of farm operators. Equipment, labor, and bedding costs were included for manure removal. Insecticide application costs included chemicals and labor for application. A typical farm with a stanchion barn had manure removal costs of $0.348 per cow per day. Recommended changes would increase costs by $0.016-0.033 per cow per day. Insecticide costs averaged $0.021 per cow per day. It may be possible to eliminate many of the insecticide applications on the farms by using the recommended 7-d manure removal practice. Even if insecticides are not eliminated entirely, increased manure removal costs would be offset by some reduction in insecticide cost. This also would have the additional benefit of greatly slowing the development of insecticide resistance by the flies.