Knockdown and mortality comparisons among spinosad-, imidacloprid-, and methomyl-containing baits against susceptible Musca domestica (Diptera: Muscidae) under laboratory conditions

The activity of spinosad, imidacloprid, and methomyl baits and technical actives were assessed against susceptible house flies, Musca domestica L. (Diptera: Muscidae). In a feeding assay, imidacloprid affected flies more rapidly than methomyl or spinosad, but spinosad was 2.7 times more potent than methomyl and 8 times more potent than imidacloprid. The profile of technical actives correlated with their respective fly bait formulations in laboratory assays. Although having the most rapid onset of activity in laboratory tests, up to 50% of flies remained alive after exposure to imidacloprid bait. In contrast, <5% of flies survived 24-h exposure to spinosad or methomyl baits. High temperature reduced the knockdown activity of imidacloprid bait and slowed the speed of kill for spinosad and methomyl baits over a 24-h exposure period. Spinosad and methomyl baits were also superior to imidacloprid when applied to the floors of environmentally controlled rooms at label recommended rates, providing good fly control for up to 21 d. The fact that a significant percentage of flies exposed to imidacloprid were rapidly knocked down but subsequently remained alive in all of the assays suggested that flies were recovering from initial exposure to this compound. Given its favorable safety profile, a high degree of initial and residual activity comparable with methomyl and lack of cross-resistance to other chemistries, spinosad bait may be a valuable component of house fly control programs to help control or delay the emergence of resistant populations.     

Susceptibility of spinosad in Musca domestica (Diptera: Muscidae) field populations

The toxicity of spinosad was determined in one susceptible and five insecticide-resistant laboratory strains of house fly, Musca domestica L. Spinosad was relatively slow-acting, but highly toxic to house flies. In a feeding bioassay, spinosad LC50 at 72 h was 0.51 microg of spinosad per gram of sugar, making it 6.3- and 3.5-fold more toxic to house flies compared with azamethiphos and methomyl, respectively. In topical application bioassay, the LD50 at 48 h of spinosad in susceptible house flies was 40 ng per 20 mg of house fly, making spinosad less toxic than the pyrethroid bioresmethrin synergized by piperonyl butoxide and the organophosphate dimethoate. The insecticide-resistant laboratory strains had resistance factors to spinosad at LC50 in feeding bioassay from 1.5 to 5.5 and at LD50 in topical application bioassay from 2.5 to 4.7, indicating that in house fly cross-resistance to the major insecticide classes will not initially be of major concern for the use of spinosad for house fly control. The toxicity of spinosad was also evaluated against 31 field populations of house flies collected from livestock farms across Denmark. The field populations were 2.2- to 7.5-fold resistant to spinosad at 72 h in feeding bioassay, but based on steep slopes in the bioassay and the limited variation of spinosad toxicity against the various field populations, we consider the field populations to be spinosad-susceptible. We propose a diagnostic dose of 12 microg of spinosad per gram of sugar in feeding bioassay with impregnated sugar for determination of resistant house flies, which is 10x the LC95 of the susceptible strain WHO and approximately = 2x the LD95 of the field populations. Spinosad showed no substantial cross-resistance to the pyrethroid bioresmethrin synergized by piperonyl butoxide, the anticholinesterases dimethoate, azamethiphos, methomyl, and spinosad in house fly field populations.     

House fly (Diptera: Muscidae) activity near baits containing (Z)-9-tricosene and efficacy of commercial toxic fly baits on a southern California dairy

Sticky card captures of house flies, Musca domestica L. (Diptera: Muscidae), were used to compare efficacy of screen-covered baits containing sugar, sugar and 0.1% (Z)-9-tricosene, sugar and 1.0% (Z)-9-tricosene, Golden Malrin [1.1% methomyl and 0.049% (Z)-9-tricosene], and Quick-Bayt [0.5% imidacloprid and 0.1% (Z)-9-tricosene]. The QuickBayt treatment caught more flies per hour (mean = 116.5) than sugar alone (mean = 81.0), but the addition of (Z)-9-tricosene to sugar did not increase fly capture compared with sugar alone. More males (65% of total) than females were collected on the sticky cards for all treatments. Fly kill by plain sugar (control) and the commercial baits Golden Malrin, QuikStrike Fly Abatement strips (1.0% nithiazine), and QuickBayt was tested over a 90-min period. An average of 1.4, 5.6, 363.0, and 1,266.0 flies were killed using sugar, Golden Malrin, QuikStrike, and QuickBayt, respectively. The similarity between Golden Malrin and plain sugar reflects severe resistance to this once effective methomyl bait. A no-choice feeding assay using lab-reared methomyl-susceptible and methomyl-resistant house flies was conducted with and without (Z)-9-tricosene. Adult mortality was significantly higher in the methomyl-susceptible strain exposed to treatments containing methomyl. Lower consumption of the methomyl treatments by resistant flies suggested resistance was behavioral and mortality was not influenced by (Z)-9-tricosene for either fly strain.     

Evaluation of metaflumizone granular fly bait for management of houseflies

The housefly, Musca domestica L. (Diptera: Muscidae), is a pest of great veterinary and public health importance. In this study, the efficacy of metaflumizone granular fly bait was assessed on first generation (F1) housefly adults raised from flies collected at a cattle feedlot in Kansas. All bioassays were conducted as choice tests, with flies having ad libitum access to water, granular sugar and bait. A commercial methomyl-based bait (Golden Malrin^TM) was used as positive control; no bait (water and granular sugar only) was used as negative control. Fly mortality was recorded on days 2, 7 and 14. The metaflumizone bait was significantly more slow-acting than the methomyl bait (mortality rates after 2 days of exposure were 49.9% and 57.9%, respectively). However, there were no significant differences in cumulative mortality later in the bioassays. Cumulative mortality rates on days 7 and 14 were 96.1% (metaflumizone), 91.4% (methomyl) and 99.0% (metaflumizone), 97.6% (methomyl), respectively. Our results demonstrate that the metaflumizone granular fly bait may be an effective modality for incorporation into management programmes for houseflies in and around livestock production facilities as well as in residential settings.     

Toxicity of spinosad in protein bait to three economically important tephritid fruit fly species (Diptera: Tephritidae) and their parasitoids (Hymenoptera: Braconidae)

The feeding toxicity of the natural insecticide spinosad in Provesta protein bait was evaluated for three economically important fruit fly species, the Mediterranean fruit fly, Ceratitis capitata (Wiedemann); the melon fly, Bactrocera cucurbitae Coquillett; and the oriental fruit fly, Bactrocera dorsalis Hendel. Both females and males were evaluated. Spinosad was remarkably similar in toxicity to all three fruit fly species. Male C. capitata (24 h LC50 values and 95% fiducial limits = 2.8 [2.60-3.0] mg/liter spinosad) were significantly, although only slightly more susceptible to spinosadthan females (4.2 [3.8-4.6] mg/liter). Male (5.5 [4.7-6.6] mg/liter) andfemale (4.3 [3.7-4.9] mg/liter) B. cucurbitae were equally susceptible to spinosad. Female (3.3 [3.1-3.6] mg/liter) and male (3.1 [2.9-3.3] mg/liter) B. dorsalis also were equally susceptible to spinosad. Provesta bait containing spinosad also was evaluated against two parasitoids of tephritid fruit flies, Fopius arisanus (Sonan) and Pysttalia fletcheri (Silvestri). These parasitoids did not feed on the bait, so a contact toxicity test was conducted. Significant amounts of mortality were found only after exposure of parasitoids to spinosad-coated glass vials with concentrations > or =500 mg/liter spinosad. Parasitoids were less susceptible than fruit flies to such a degree that use of spinosad in bait spray should be compatible with these parasitoid species. Because the fruit flies tested in this study were so susceptible to spinosad, this product seems to be promising as a bait spray additive and a replacement for malathion for control of these species.     

Feeding and foraging of wild and sterile Mediterranean fruit flies (Diptera: Tephritidae) in the presence of spinosad bait

The sterile insect technique (SIT) is used to control wild Mediterranean fruit fly introductions in California and Florida in the U.S. In the past, bait sprays containing malathion proved invaluable in treating new outbreaks or large populations before the use of SIT. Recently, a spinosad protein bait spray, GF-120, has been developed as a possible alternative to malathion, the standard insecticide in protein bait sprays. In this study, protein-deficient and protein-fed Vienna-7 (sterile, mass-reared, "male-only" strain) flies and wild males and females were evaluated to determine the effectiveness of the GF-120 protein bait containing spinosad with respect to bait attraction, feeding, and toxicology. There were no effects of diet or fly type on feeding duration in small laboratory cages. Wild flies, however, registered more feeding events than Vienna-7 males. Flies that fed longer on fresh bait died faster. Protein-deficient flies were more active and found the bait more often than protein-fed flies. Data suggest that adding protein to the diet of SIT flies may decrease their response to baits, therefore, reduce mortality, and thus, allow the concurrent use of SIT and bait sprays in a management or eradication program.     

Effects of disodium octaborate tetrahydrate on survival, behavior, and egg viability of adult muscoid flies (Diptera: Muscidae).

Disodium octaborate tetrahydrate (Na2B8O13(.)4H2O) was mixed with sugar and fed to adult Musca domestica L. and Fannia canicularis (L.) to determine concentration-mortality relationships. LC50s (48-h exposure) were 5.7% for M. domestica and 1.0% for F. canicularis. Rates of 1 and 2% were used to test effects on M. domestica mortality and egg hatch over an 8-d period. Reduced egg hatch was evident after 1 d of feeding on the treated mixtures and was greatest (less than 10% egg hatch) after flies fed only on treated mixtures for 2 d. A partial rebound in egg hatch occurred after 3-4 d of feeding on treated diet. Sperm motility in females fed treated sugar was apparently normal. Fertile egg placed on treated poultry manure did not hatch, indicating embryonic death, which also may have been involved in the low hatch of eggs observed from treated flies. When flies were exposed to treated sugar for 2 d then returned to untreated diet, delayed mortality effects and reduced egg hatch persisted for at least 3 d. Behavioral assays (feeding) with M. domestica demonstrated that flies rejected borate-sugar mixtures in favor of sugar alone when the concentration of borate was greater than 2%. Given a choice of treated and untreated poultry manure for oviposition, flies also rejected the treated manure. The potential of borates in adult bait formulations or applied to developmental substrates for fly control is discussed.     

Does behaviour play a role in house fly resistance to imidacloprid‐containing baits?

The objective of this research was to examine the role and type of behavioural mechanisms that function in house fly, Musca domestica L. (Diptera: Muscidae), resistance to an imidacloprid‐containing commercial fly bait, QuickBayt^®, using an insecticide‐susceptible and an imidacloprid‐resistant strain. Mortality and feeding behaviour were observed through choice bioassays of three post‐imidacloprid selected house fly generations to determine whether flies would consume the bait in the presence of an alternative food source. Mortality rates in choice containers progressively decreased in post‐selection flies as QuickBayt^® no‐choice selections proceeded. There were no differences between the proportions of flies observed contacting QuickBayt^® and sugar, respectively, a finding that eliminates repellency as a mechanism of stimulus‐dependent behavioural resistance. However, differences in QuickBayt^® consumption and subsequent mortality between choice and no‐choice containers provided strong support for the evolution of consumption irritancy‐ or taste aversion‐related behavioural resistance. The results of this study support the responsible rotation of insecticide bait formulations for house fly control.     

Differential expression of CYP6A5 and CYP6A5v2 in pyrethroid-resistant house flies, Musca domestica

Two cytochrome P450 alleles, CYP6A5 and CYP6A5v2, were isolated from a pyrethroid-resistant house fly stain, ALHF. The two alleles shared 98% similarity in amino acid sequence. To understand the importance of these two alleles in resistance and examine the expression profile of the two alleles between resistant and susceptible strains, quantitative real-time PCR (qRT-PCR) was performed and compared with the Northern blot analysis. We found that qRT-PCR was an efficient method to characterize the expression profiles between these two sequence-closely-related P450 genes between resistant and susceptible houses flies. One of them, CYP6A5v2, was constitutively overexpressed in ALHF house flies compared with susceptible house fly strains. Moreover, this gene was predominantly expressed in the abdominal tissues of ALHF, in which the primary detoxification organs of insects are located. However, there was no significant difference in the expression of CYP6A5 between ALHF and susceptible house flies. The genetic linkage analysis was conducted to determine the possible link between the constitutively overexpressed CYP6A5v2 and insecticide resistance. CYP6A5v2 was mapped on autosome 5, which is correlated with the linkage of resistance in ALHF. Taken together, the study suggests the importance of CYP6A5v2 in increasing metabolic detoxification of insecticides in ALHF. The distinct expression of CYP6A5 and CYP6A5v2 in resistant and susceptible house flies implies the functional difference of theses two genes in house flies and suggests that they are two recently diverged P450 genes presented in a single organism.     

Behavioral responses of Rhagoletis cingulata (Diptera: Tephritidae) to GF-120 insecticidal bait enhanced with ammonium acetate

GF-120 is a baited formulation of the insecticide spinosad containing 1% ammonium acetate, developed for control of economically important fruit flies. The response of feral cherry fruit flies, Rhagoletis cingulata Loew, to GF-120 augmented with 0, 5, or 10% ammonium acetate was evaluated under orchard conditions. Significantly more flies were observed within 30 cm of bait droplets with 10% ammonium acetate added compared with standard bait or to a water control. These fly visits to GF-120 enhanced with 10 or 5% ammonium acetate lasted an average of 263.2 +/- 85.2 and 337.6 +/- 72.6 s, respectively, compared with 50.3 +/- 36.4 s for standard GF-120. Droplets containing additional ammonium acetate also were contacted by more flies, and more flies fed upon these droplets than on GF-120 or the water control. Furthermore, the duration of feeding on GF-120 bait enhanced with either level of additional ammonium acetate was significantly greater compared with standard GF-120 or water. Feeding events lasted between 61.5 +/- 30.7 and 73.4 +/- 21.0 s on enhanced GF-120 compared with 6.8 +/- 5.7 s on standard GF-120. Collectively, these results indicate that the interaction of feral R. cingulata with GF-120 droplets and the toxicant spinosad can be increased by addition of ammonium acetate.     

Susceptibility of house flies (Diptera: Muscidae) and five pupal parasitoids (Hymenoptera: Pteromalidae) to abamectin and seven commercial insecticides.

Assays of five commercial insecticides applied as residual sprays at label rates to plywood indicated the most toxic insecticide overall for pteromalid parasitoids of house flies, Musca domestica L., was Atroban (permethrin), followed by Ciodrin (crotoxyphos), Rabon (tetrachlorvinphos), Ectrin (fenvalerate), and Cygon (dimethoate). Insecticide-susceptible house flies were susceptible to all five insecticides (mortality, 62-100%). Flies that were recently colonized from populations on dairy farms in New York were susceptible only to Rabon. Urolepis rufipes (Ashmead) was the most susceptible parasitoid species overall to these insecticides, followed by Muscidifurax raptor Girault & Sanders, Nasonia vitripennis Walker, Pachycrepoideus vindemmiae (Rondani), and Spalangia cameroni Perkins. Compared with susceptible flies, newly colonized flies showed moderate resistance to avermectin B1a (abamectin). Abamectin was more toxic to all of the parasitoids except N. vitripennis and S. cameroni than to newly colonized house flies when exposed for 90 min to plywood boards treated with 0.001-0.1% abamectin. Space sprays with Vapona (dichlorvos) killed all of the parasitoids and susceptible flies and 64% of the newly colonized flies when insects were placed directly in the path of the spray; mortality was substantially lower among flies and parasitoids protected under 5 cm of wheat straw. Space sprays with Pyrenone (pyrethrins) killed greater than 86% of all insects exposed to the spray path except for the newly colonized flies (1% mortality); mortality of insects protected under straw was low (less than 12%) except for S. cameroni (76%). Because responses of the five parasitoids to the different insecticides varied considerably, general conclusions about parasitoid susceptibility to active ingredients, insecticide class, or method of application were not possible.     

Biochemical genetics of altered acetylcholinesterase resistance to insecticides in the house fly

Resistance to the organophosphate insecticide tetrachlorvinphos was examined in a house fly (Musca domestica L.) strain with an altered acetylcholinesterase (AChE) of decreased sensitivity to inhibition by the insecticide. Genetic tests showed that both resistance and the altered AChE were controlled by semidominant gene(s) on chromosome II. The gene for resistance was five crossover units from the mutant marker stubby wing (stw). A house fly strain was prepared in which resistance was introduced in to a susceptible stw strain by recombination. Biochemical assays revealed that the altered AChE was introduced along with resistance. Assays of the AChE of resistant and susceptible stw strains by two independent methods showed that the enzyme from resistant flies was 30 times more slowly inhibited by tetrachlorvinphos than the enzyme from susceptible flies.This work was supported in part by NIH Grant ES 00901.Technical Article 13340, Texas Agricultural Experiment Station.     

Relative developmental and reproductive fitness associated with pyrethroid resistance in the major southern African malaria vector, Anopheles funestus

The effect of pyrethroid resistance on the fitness of a laboratory strain of Anopheles funestus originating from southern Mozambique was evaluated by comparing the developmental and reproductive characteristics of a pyrethroid resistant strain with an insecticide susceptible strain. Fitness was evaluated in terms of fecundity, fertility, egg production, developmental time and life stage progression and survival. Of the eggs laid by females of the resistant strain, 81.5% hatched while only 66.9% were recorded in the susceptible strain. The time from egg hatch to adult emergence was longer for the resistant strain (15.9 days) than the susceptible strain (15.2 days). A significantly higher proportion of eggs from the resistant strain (61.6%) survived to adulthood compared with those of the susceptible strain (49%). Fecundity and larval and pupal survival did not differ significantly between strains. Of spermathecae dissected from females of the resistant strain, 56.8% were fertilized compared to 52.6% from the susceptible strain. The proportion of females that successfully produced eggs was 43.3% and 23.3% for the resistant and susceptible strains respectively. Complete failure of larval hatch was recorded in 28.6% of susceptible strain families compared to 7.7% of resistant families. Our results show that pyrethroid resistance in southern African An. funestus does not incur any loss of fitness under laboratory conditions. These results suggest that the removal of pyrethroid insecticide selection pressure may not lead to a regression of resistance alleles in pyrethroid resistant An. funestus populations in southern Africa.     

Efficacy of abamectin fed to German cockroaches (Dictyoptera: Blattellidae) resistant to pyrethroids

Ten field-collected strains of the German cockroach, Blattella germanica (L.), with varying levels of pyrethroid resistance were tested for possible cross-resistance to abamectin administered as a bait. The time-mortality method was used for comparison of response with a known susceptible strain in 10-d feeding experiments. Essentially no resistance to abamectin was found. Extensive feeding inhibition occurred after a few days, but the amount of abamectin consumed varied substantially from strain to strain. Abamectin may have considerable potential as a cockroach bait insecticide.     

Deltamethrin‐induced feeding plasticity in pyrethroid‐susceptible and ‐resistant strains of the maize weevil,Sitophilus zeamais

Phenotypic plasticity contributes to the adaptative evolution of populations exposed to new or altered environments. Feeding plasticity is a component of phenotypic plasticity not usually considered in insect strains adapted to insecticide‐altered environments, but which may either accentuate or mitigate insecticide resistance. This is a concern in the pyrethroid‐resistant strains of the maize weevil Sitophilus zeamais Motsch. (Col., Curculionidae), and the reason for this study. A pyrethroid‐susceptible and two pyrethroid‐resistant strains of maize weevil were subjected to free‐choice and no‐choice tests with maize grains sprayed with increasing doses of the pyrethroid, deltamethrin. The insects from the pyrethroid‐resistant strains exhibited higher feeding avoidance with increased deltamethrin doses than insects from the susceptible strain when subjected to free‐choice tests. The strains of maize weevil physiologically resistant to pyrethroids were also behaviourally resistant to deltamethrin – an additional management concern. The resistant strains avoid deltamethrin‐sprayed grains and are less nutritionally affected by this compound, with divergent responses from the susceptible strain with increased doses of deltamethrin. Furthermore, the higher relative growth rate and consequently higher efficiency of food conversion observed in the insecticide‐resistant strains were significant even without insecticide exposure, indicating that these traits are stimulus‐independent and may persist even without further insecticide selection, potentially limiting the options available for their management.     

家蝇中乙酰胆碱酯酶、羧酸酯酶和多功能氧化酶活性与抗药性的关系

本文对几种抗药性和敏感性家蝇品系的乙酰胆碱酯酶(AChE)、羧酸酯酶及多功能氧化酶(MFO)进行了测定.结果表明:①抗药性品系和敏感性品系的AChE活力差异不大, 有机磷抗性品系的AChE对对氧磷的不敏感性比敏感性家蝇明显增大.②某些抗药性家蝇的羧酸酯酶活力比敏感性家蝇大.③抗药性家蝇的MFO活力(O-脱甲基和环氧化)比敏感性家蝇均有不同程度的增高.④二氯苯醚菊酯抗性家蝇对有机磷有负交互抗性.     

Insecticide-insensitive acetylcholinesterase from a laboratory selected and a field strain of housefly (Musca domestica) (L.)

1. Acetylcholinesterase from the heads of a strain of houseflies selected for resistance to the carbamate insecticide methomyl, and from a methomyl-resistant field strain was found to be less sensitive to inhibition by methomyl than that from a susceptible strain. 2. The enzyme from resistant insects was also more tolerant to malaoxon, dichlorvos and bomyl but not to azamethiphos. 3. The decrease in sensitivity to inhibition appeared to be due to an increase in affinity for substrate.     

The efficacy of entomopathogenic nematodes for controlling housefly infestations of intensive pig units

The efficacy of the entomopathogenic nematodes Steinernema feltiae and Heterorhabditis megidis after formulation into a housefly bait was compared with a commercial bait formulation of methomyl for the control of houseflies in a U.K. pig farm. The housefly infestation was confined to the farrowing unit, which consisted of ten farrowing houses, where two adjacent houses were sequentially re-stocked with pregnant sows at weekly intervals. Shortly after re-stocking, one house was baited with one of the nematode species and the other with methomyl. Significantly fewer flies ( P < 0.05) were counted in the houses baited with either S. feltiae or H. megidis than those baited with methomyl. The efficacy of S. feltiae sprayed on to the manure was also compared with methomyl bait. Counts of houseflies carried out in the farrowing cycle before this treatment were not significantly different ( P > 0.05); however, significantly fewer flies ( P < 0.05) occurred after S. feltiae was sprayed. The efficacy of encapsulated S. feltiae was also compared with methomyl bait and no significant difference was observed ( P > 0.05).