Genetics of organophosphate resistance in field populations of the house fly (Diptera: Muscidae)

The genetics of resistance to the organophosphate insecticide diazinon were investigated in four populations of the house fly, Musca domestica L., collected in the southern United States. Crosses were made between individual females of lines derived from each population and males of a susceptible strain with three recessive mutants on chromosome II. Individual F1 females were crossed to mutant males, and the progenies were scored for resistance to diazinon and for the presence of mutant phenotypes. A major chromosome II gene for resistance to diazinon was present in all populations at an overall frequency of 83%. Map distances between the resistance gene and the mutant aristapedia and between the mutants aristapedia and stubby wing were highly variable in all populations. Recombination among the visible mutants was usually reduced in resistant progenies relative to susceptible progenies. The data suggest that a single major gene for resistance to diazinon was present on chromosome II in all test populations at variable map positions and is usually associated with a chromosome rearrangement, probably an inversion. The results are similar to those obtained earlier with house fly populations selected for resistance to insecticides in the laboratory; therefore, they seem to be characteristic of field and laboratory populations of the house fly. Overall, the data offer an explanation for previous results suggesting the existence of multiple, closely linked genes for metabolic resistance to insecticides on house fly chromosome II.     

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.     

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.     

Cyromazine resistance in the house fly (Diptera: Muscidae): genetics and cross-resistance to diflubenzuron

Larvae of a house fly, Musca domestica L., strain collected in a chicken house near Pittsburg, Tex, after a control failure with the poultry feedthrough insecticide cyromazine showed 6.5-fold resistance to cyromazine and 10-fold resistance to diflubenzuron. Adults of the strain showed high levels of resistance to carbaryl, DDT, and diazinon; moderate resistance to cypermethrin and permethrin; and low resistance to dieldrin. In contrast, no resistance to cyromazine was observed in eight laboratory house fly strains with resistance to four groups of conventional insecticides. When the genetics of cyromazine resistance was investigated in crosses to susceptible strains with visible mutant markers, results indicated cyromazine resistance was incompletely dominant over susceptibility and the resistance gene was on chromosome V. The same or a closely linked gene conferred resistance to diflubenzuron. A strain containing only chromosome V from the original resistant strain was resistant to cyromazine and diflubenzuron, but not to other insecticides except for low level resistance to DDT and carbaryl. Resistance to the latter insecticides appeared to be due to a linked, but distinct, gene. Therefore, resistance to cyromazine and probably diflubenzuron appears to be genetically distinct from other types of insecticide resistance.     

Condensed tannins inhibit house fly (Diptera: Muscidae) development in livestock manure

Reducing chemical use for suppressing internal and external parasites of livestock is essential for protecting environmental health. Although plant condensed tannins are known to suppress gastro-intestinal parasites in small ruminants, no research on the effects of tannins on external arthropod populations such as the house fly, Musca domestica L., have been conducted. We examined the impact of plant material containing condensed tannins on house fly development. Prairie acacia (Acacia angustissima (Mill.), Kuntze variety hirta (Nutt.) B.L. Rob.) herbage, panicled tick-clover (Desmodium paniculatum (L.) DC.) herbage, and quebracho (Shinopsis balansae Engl.) extracts were introduced at rates of 1, 3 or 5% condensed tannins/kg beef cattle, dairy cattle, and goat manure, respectively. In a second experiment, we also introduce purified catechin at 1 or 3% of dairy manure dry matter and measured its impact on house fly development. For the house flies used in these experiments, the following was recorded: percent fly emergence (PFE), average daily gain (ADG), and average fly weight (AFW). No effects (P>0.05) in house fly development were measured in the caprine manure. Prairie acacia (20.9% condensed tannins) had no effect on house flies developing in either bovine manures. Tick clover (4.9% condensed tannins) had a negative effect on all three quantifiable variables of house fly development in the bovine manures, whereas quebracho extract (64.0% condensed tannins) at the 3 and 5% rate reduced fly emergence in beef manure and average daily gain in dairy manure. The application of purified catechin at 3%, but not 1%, reduced fly PFE, ADG, and AFW.     

Horn fly (Diptera: Muscidae) insecticide resistance in Kentucky and Arkansas

The effect of previous insecticide use patterns for horn fly control on the susceptibility spectrum of horn fly (Haematobia irritans [L.]) populations from Kentucky and Arkansas is described. Populations of horn flies from both states were tested with three pyrethroids (cyhalothrin, cypermethrin, and permethrin), three organophosphates (diazinon, pirimiphos methyl, and tetrachlorvinphos), and a chlorinated hydrocarbon (methoxychlor). Dose-mortality data indicated insecticide resistance in Arkansas and Kentucky. Two permethrin-resistant horn fly populations in Kentucky that did not have a history of exposure to methoxychlor were cross-resistant to this chlorinated hydrocarbon. Horn fly populations from both states with a history of at least three consecutive years of exposure to various pyrethroid ear tags were subsequently exposed to cattle tagged with cyhalothrin-impregnated ear tags for 15-16 wk. Such exposure resulted in a decrease in susceptibility to this pyrethroid (ranging from approximately 30 to greater than 100-fold) when compared with levels before treatment. Horn fly populations from Arkansas resistant to cyhalothrin (as a result of exposure to cyhalothrin ear tags) were cross-resistant to pirimiphos methyl. Seasonal exposure of an Arkansas and Kentucky horn fly population to cattle with ear tags impregnated with pirimiphos methyl resulted in a significant decrease in susceptibility to this organophosphate.     

Azadirachtin as a larvicide against the horn fly, stable fly, and house fly (Diptera: Muscidae)

Effects of azadirachtin, a triterpenoid extracted from neem seed, Azadirachta indica A. Juss., were similar to those of insect growth regulators against the immature stages of the born fly, Haematobia irritans (L.), the stable fly, Stomoxys calcitrans (L.), and the house fly, Musca domestica L. When an ethanolic extract of ground seed was blended into cow manure, LC50 and LC90's for larval horn flies were 0.096 and 0.133 ppm azadirachtin, respectively. An emulsifiable concentrate (EC) had an LC50 for larval horn flies of 0.151 ppm and an LC90 of 0.268 ppm. For larval stable flies, the EC formulation had an LC50 of 7.7 ppm and an LC90 of 18.7 ppm azadirachtin in manure. Against larval house flies, the LC50 and LC90 were 10.5 and 20.2 ppm, respectively. When the EC formulation was administered orally to cattle at a rate of greater than or equal to 0.03 mg azadirachtin per kg of body weight per day or when ground neem seed was given as a daily supplement of greater than or equal to 10 mg seed per kg body weight, horn fly development in the manure was almost completely inhibited. In contrast, ground seed mixed in cattle feed at the rate of 100-400 mg seed per kg of body weight per day caused less than 50% inhibition of stable flies in the manure.     

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.     

Linkage analysis of an acetylcholinesterase gene in the house fly Musca domestica (Diptera: Muscidae)

Linkage of an acetylcholinesterase (AChE) gene was detected in the house fly, Musca domestica L., by using the backcross method between a strain, aabys, that had a morphological multichromosomal marker on each of the five autosomes and a wild strain, LPR. Both strains were homozygous in this gene, and we used eight single nucleotide polymorphisms (SNPs) between them to distinguish the parental sequences in the backcrossed progeny, two of which resulted in the amino acid substitiutions common to the Drosophila and Aedes AChEs insensitive to organophosphates and carbamates. F, appeared to be a wild phenotype, and the AChE gene was heterozyous of aabys and LPR. In the backcross progeny, 32 (2(5)) phenotypes appeared, and 10 phenotypes with one wild or morphological marker were picked up for genotyping by the SNPs of AChE gene. A combination of the morphological markers and the SNPs revealed that the AChE structural gene is linked to autosome 2 in the house fly.     

Effect of airflow on house fly (Diptera: Muscidae) distribution in poultry houses.

Numbers of fecal and vomit spots deposited by house flies, Musca domestica L., on spot cards were about twice as high on cards placed on the downwind sides as on the upwind sides of building support posts in caged-layer poultry houses with tunnel ventilation in Brooksville, FL. This trend was stronger at the ends of the houses where airflow is faster than in the relatively still-air center of the houses. A similar evaluation conducted in a pullet house (Zephyrhills, FL) with an evaporative cooling ventilation system revealed significantly higher fly counts on spot cards and sticky cards in downwind compared with upwind orientations. Flies in the pullet house were concentrated in both ends of the house and in the center, with comparatively fewer flies in the intermediate regions. There was a high degree of correlation between spot card and sticky card counts in the pullet house.     

A cline in frequency of autosomal males is not associated with insecticide resistance in house fly (Diptera: Muscidae)

Geographic variation in the chromosomal location of the male sex determining factor (M) was studied in four house fly, Musca domestica L., populations from the eastern United States. We found a strong clinal trend (29 degrees 41' latitude in Florida to 44 degrees 2' in Maine) in which the percentage of standard XY(M) males increased with increasing latitude. In Florida, 100% of the males possessed the M factor on the third autosome (III(M)). North Carolina had 20% III(M) males and 2.35% with both Y(M) and III(M). Fewer III(M) males were found in New York (4.35%). Populations from Maine contained 100% XY(M) males. In two of three standard laboratory-susceptible strains, all males carried M on an autosome ("autosomal males" or A(M)): CS (III(M)) and SRS (V(M)). Insecticide bioassays of four field-collected strains led us to conclude that resistance is not correlated with sex determination over a broad range of insecticides. For example, high levels of resistance to permethrin (86-99% survival at a diagnostic concentration) were found in all four field-collected strains. The five other insecticides evaluated showed varying levels of resistance among field strains. We conclude that a cline is present in house fly populations from the eastern United States with 100% III(M) males in the south and entirely Y(M) males in the north and that insecticide resistance is not a key factor influencing the evolution or linkage of M.     

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.