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At least 19 recordsLinked to original sources

PubMed2004

Significance of the sulfonylurea receptor (SUR) as the target of diflubenzuron in chitin synthesis inhibition in Drosophila melanogaster and Blattella germanica.

Diflubenzuron (DIMILIN) is a powerful insecticidal chemical which has been known for many years to inhibit chitin synthesis in vivo in insects and related arthropod species. However, its action mechanism has remained unresolved partly because of its inaction on any of the enzymes involved in chitin synthesis in vitro. Based on our previous work (Diflubenzuron affects gamma-thioGTP stimulated Ca2+ transport in vitro in intracellular vesicles from the integument of the newly molted American cockroach, Periplaneta americana L. Insect Biochem. Mol. Biol. 24 (1994) 1009) showing that diflubenzuron inhibits Ca2+ uptake by vesicles obtained from the integument of American cockroach, Periplaneta americana (L.), in vitro, we tested the hypothesis that the action site of diflubenzuron is an ABC (ATP binding cassette) transporter, probably a sulfonylurea-sensitive transporter. Glibenclamide, one of the most commonly used sulfonylureas for type II diabetes treatment, was the positive control. When given to immature insects, glibenclamide clearly caused toxicity, with symptoms indicating molting abnormality comparable to diflubenzuron. Its LD50 (0.472 microg/nymph) was approximately 2.8 times the value obtained for diflubenzuron (0.17 microg/nymph, topical) in German cockroach, Blattella germanica (L.). However, in terms of the inhibitory activities on chitin synthesis, in isolated integuments glibenclamide showed an identical potency to diflubenzuron in B. germanica nymphs. A competitive binding assay with [3H]-glibenclamide and unlabeled diflubenzuron clearly established that the latter is capable of competitively displacing the former radioligand. The KD values observed for vesicles prepared from fruit fly larvae, Drosophila melanogaster M., were 44.9 nM for glibenclamide and 65.0 nM for diflubenzuron, respectively. Furthermore, glibenclamide was found to affect Ca2+ uptake by isolated cuticular vesicles from B. germanica in a manner very similar to diflubenzuron. These results support our conclusion that the sulfonylurea receptor (SUR) is the target of diflubenzuron in inhibition of chitin synthesis in these two insect species.

ATP-Binding Cassette Transporters↗

PubMed2002

The stability and persistence of diflubenzuron in marine sediments studied under laboratory conditions and the dispersion to the sediment under a fish farm following medication.

A high performance liquid chromatographic (HPLC) method was developed to determine the concentration of diflubenzuron, a delousing agent used in fish farming, in marine mud and shell sand. The recovery of diflubenzuron from mud was 100.8+/-1.1% and 105.5+/-4.3% for shell sand. The limit of quantitation was found to be 0.1 microg g(-1). The stability of diflubenzuron was studied under laboratory conditions in marine sediments at different temperatures (4 and 14 degrees C). No degradation of diflubenzuron occurred in the organic rich mud sediment or in the shell sand sediment during the experimental period of 204 days. Increasing the temperature from 4 to 14 degrees C had no effect on the stability. Furthermore, diflubenzuron showed to be persistent in both mud and shell sand sediment since no detectable diffusion from the sediment to the water phase occurred during the experimental period of 204 days. Increasing the water current in the tanks had no effect on the persistence. Under field conditions, the concentrations of diflubenzuron found in the organic material from sediment traps placed 2 m from the bottom under the cage in a fish farm during medication were high and ranged from 71 to 259 microg g(-1). The concentrations of diflubenzuron in the sediment under the fish farm were, however, low, with a maximum concentration of 5.4 microg g(-1). The dispersion of diflubenzuron to the sediment was limited to less than 20 m from the edge of the cage in every direction. Fifteen months following the medication, only traces (< 0.1 microg g(-1)) of diflubenzuron were detected in the sediment under the fish farm. Possible explanations for this decrease are resuspension and redistribution of sediment and/or oxic degradation of the drug.

Animals↗

PubMed2006

Characterization of a chitin synthase cDNA and its increased mRNA level associated with decreased chitin synthesis in Anopheles quadrimaculatus exposed to diflubenzuron.

Chitin synthase (EC 2.4.1.16) is a crucial enzyme responsible for chitin biosynthesis in all chitin-containing organisms. This paper reports a complete cDNA encoding chitin synthase 1 (AqCHS1), change of AqCHS1 mRNA level in response to diflubenzuron exposure, and concentration-dependent effect of diflubenzuron on chitin synthesis in the common malaria mosquito (Anopheles quadrimaculatus). The cDNA consists of 5723 nucleotides, including an open reading frame (ORF) of 4734 nucleotides that encode 1578 amino acid residues and a non-translated region of 989 nucleotides. The deduced amino acid sequence contains all the chitin synthase signature motifs (EDR, QRRRW and SWGTR) and shows 97% identity to that of An. gambiae (AgCHS1, XM_321337). Northern blot and real-time quantitative PCR analyses revealed a significant increase of AqCHS1 mRNA level in the larvae exposed to diflubenzuron at 100 and 500 microg/L. As confirmed by real-time quantitative PCR, AqCHS1 mRNA level was enhanced by 2-fold in the larvae exposed to diflubenzuron at 500 microg/L for 24 h. In contrast, exposures of the larvae to diflubenzuron at 4.0, 20, 100 and 500 microg/L for 48 h resulted in decreases of chitin content by 9.0%, 43%, 58% and 76%, respectively. Significantly increased AqCHS1 mRNA level associated with decreased chitin synthesis may imply possible inhibition of chitin synthase, or abnormal chitin synthase translocation or chitin microfibril assembly conferred by diflubenzuron. Increased AqCHS1 expression due to increased transcription and/or increased mRNA stability may serve as a feedback mechanism to compensate such an effect in the mosquitoes. Further studies are necessary to elucidate the relationship between reduced chitin synthesis and increased expression of AqCHS1 in order to shed new light on trafficking and regulation of chitin biosynthesis in the mosquito affected by diflubenzuron.

Amino Acid Sequence↗

PubMed2000

Effect of diflubenzuron on flight of adult aquatic insects (Plecoptera, Trichoptera) following emergence during the second year after aerial application.

With Malaise traps, we monitored the flight of adult Plecoptera and Trichoptera following emergence from headwater streams in the Fernow Experimental Forest, WV, during the second year after application of diflubenzuron. We placed five traps at various distances from each stream during May through September of 1991, 1992, and 1993. We collected pretreatment samples during the first year. In May 1992, diflubenzuron was applied to two watersheds, and the other two watersheds were used as untreated references. The 1992 study tested the effects of diflubenzuron that fell directly into the streams or were washed into the stream during the first year. For 1993, we tested the hypothesis that diflubenzuron affected adult flight following emergence during the year following abscission and possible ingestion of the treated leaves. The analysis compared the regressions of the number of adults caught in each trap versus distance of the trap from the stream among years and between treatments for each species. The flight of the stonefly Leuctra ferruginea (Walker) was reduced in the treatment watersheds compared with the reference watersheds during the year following abscission of the treated leaves. Adult flight of other species did not decrease in the treatment watersheds during 1993. These results show a relatively small effect of diflubenzuron on these aquatic insects; however, our study involved only a single application of diflubenzuron. Additional research may be needed to predict the possible effects of multiple applications of diflubenzuron over several years as often occurs during actual efforts to suppress gypsy moth, Lymantria dispar (L.).

Animals↗

PubMed1999

Field assessment of Beauveria bassiana (Balsamo) vuillemin and potential synergism with diflubenzuron for control of savanna grasshopper complex (Orthoptera) in Mali.

In large-scale field trials in Mali, formulated conidia of Beauveria bassiana (Balsamo) Vuillemin strain GHA were tested against unconfined grasshopper populations in field plots of 10 ha each. The trials compared B. bassiana conidia formulated in a mineral oil carrier, formulated diflubenzuron, a combination of B. bassiana plus formulated diflubenzuron, and fenitrothion. A total of 30 different species of grasshoppers occurred in the experimental plots, of which 3 were dominant in all plots, namely, Cryptocatantops haemorrhoidalis (Krauss), Acrotylus blondeli (Saussure), and Hieroglyphus daganensis (Krauss). The density of grasshopper populations in the plots was determined by the number of grasshoppers counted in 0.1-m2 rings laid out in repeated transects. All treatments significantly reduced the grasshopper densities in the experimental plots compared to the untreated controls. After 14 days posttreatment the grasshopper populations decreased by 38.1% in plots treated with B. bassiana alone, 29.4% in plots treated with diflubenzuron alone, and 55.6% in plots treated with the B. bassiana plus diflubenzuron. Effects of the diflubenzuron-B. bassiana mixture were additive and not synergistic. In the fenitrothion plots, after a drop of 95.5% within the first 48 h after the treatment, the grasshopper population steadily increased at a rate of 12.4% per day for the remainder of the 14-day period, whereas densities in the other treated plots continued to decrease. These trials suggest that B. bassiana, with or without a diflubenzuron additive, exerts a continuous effect over a prolonged period.

Animals↗

PubMed1987

Simulation of fly-waves to assess the ability of diflubenzuron to protect sheep against flystrike by Lucilia cuprina.

Sheep were exposed to mass-released gravid females of the sheep blowfly, Lucilia cuprina, in a fly-proof animal house at various times after treatment with the insecticide diflubenzuron (1000, 1500 and 2500 ppm a.i.). Untreated sheep were similarly exposed as controls, while sheep treated with either diazinon (400 ppm a.i.) or cyromazine (1000 ppm) were used as standards for comparison. Before exposure, groups of sheep were wetted by simulating rainfall in the animal house in order to increase their susceptibility to flystrike by L. cuprina. In one trial, sheep jetted with either diflubenzuron or cyromazine (both at 1000 ppm) were protected against flystrike for at least 110 days. At 1500 ppm, diflubenzuron performed significantly better with no bodystrike occurring in the group until the end of the trial at 170 days. Under more severe fly pressure in a second trial diflubenzuron at concentrations up to 2500 ppm provided the same protection as diazinon (approximately 56 days), but performed significantly better thereafter. No cross-resistance to diflubenzuron was found in diazinon-resistant field populations of L. cuprina in laboratory bioassays. The data show that diflubenzuron would be suitable as a prophylactic treatment for flystrike.

Animals↗

PubMed2006

Residues of diflubenzuron on horse chestnut (Aesculus hippocastanum) leaves and their efficacy against the horse chestnut leafminer, Cameraria ohridella.

Residues of the insect growth regulator diflubenzuron were quantified on horse chestnut (Aesculus hippocastanum L.) leaves treated with a diflubenzuron 480 g litre(-1) SC, Dimilin. To analyse the samples, an analytical procedure was developed involving a simple extraction step followed by high-performance liquid chromatography on an octadecyl-modified silica column with methanol + 0.01 M ammonium acetate mobile phase. The results showed diflubenzuron to be highly stable on horse chestnut leaves; more than 4 months (127 days) after application, 38% (on average) of the insecticide still remained on/in the leaves. The data confirmed biological observations showing diflubenzuron's long-term efficacy against the horse chestnut leafminer, Cameraria ohridella Deschka and Dimić, which is the most important pest of the horse chestnut in Europe. The hypothesis of possible penetration of diflubenzuron into the leaf mass is explored and discussed.

Aesculus↗

PubMed2003

Horizontal and trophic transfer of diflubenzuron and fipronil among grasshoppers (Melanoplus sanguinipes) and between grasshoppers and darkling beetles (Tenebrionidae).

The possibility of horizontal transmission of diflubenzuron and fipronil was assessed in rangeland grasshoppers. Laboratory studies of Melanoplus sanguinipes demonstrated that fipronil was horizontally transferred at lethal levels (p < 0.05) via cannibalism through four passages when the initial dose applied to a food source was 250 times the label rate for rangeland grasshopper and locust control (label rate is 4 g AI/ha). Mortality was 100% on the first three passages through cannibalism. At 25 and 1 times the label rate, fipronil was lethal (p < 0.05) only on the first cannibalistic passage. Diflubenzuron generated significant (p < 0.05) mortality via horizontal transmission through two passages when the initial dose applied to a food source was 2,000 times the label rate for rangeland grasshopper control (label rate is 8.71 g AI/ha). There was 100% mortality in the first passage via cannibalism. At 250 and 25 times the label rate, diflubenzuron was lethal only on the first cannibalistic passage. Field applications of these two acridicides followed by collection of cadavers (Amphitornus coloradus and Ageneotettix deorum) that were fed to M. sanguinipes in the laboratory revealed that fipronil (25 times the label rate) generated significant (p < 0.05) mortality through two passages and diflubenzuron (label rate) caused no mortality via necrophagy. Tenebrionid beetles fed grasshopper cadavers collected from the field application of fipronil yielded 45% mortality, compared with 25% mortality in the controls. These findings suggest that horizontal and trophic transfer probably play a nominal ecotoxicological role in rangeland grasshopper control programs with diflubenzuron, but the transfer of fipronil to grasshoppers, scavengers, and natural enemies via necrophagy may increase both the efficacy of control programs and their environmental affects.

Animals↗

PubMed1997

Determination of diflubenzuron in apples by gas chromatography.

A method for the determination of residues of the insecticide diflubenzuron, 1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea, in apples using gas chromatography with electron-capture detection has been developed and validated. The three solvents ethyl acetate, acetone and dichloromethane were tested for extraction of diflubenzuron residues from apples. Dichloromethane gave the highest recovery and the lowest background and was chosen as the extraction solvent. After extraction the residue of diflubenzuron was derivatized with heptafluorobutyric anhydride. The derivative was purified by silica solid-phase extraction using toluene as the eluent. The external standard calibration was linear over the range 0.05-1.0 microgram/ml and the limit of quantification was 0.03 mg/kg apple using 25 g samples. Recovery of diflubenzuron from spiked apples (0.1-0.8 mg/kg) was 80-88% with a relative standard deviation of less than 10% (n = 5). The method was applied to the determination of diflubenzuron residues in apples from a treated field.

Acetates↗

PubMed1992

Bioavailability, biological activity and characterization of bound residues of diflubenzuron in wheat.

Wheat grain was treated with radiolabeled diflubenzuron at 100 ppm and stored for various periods; up to 6 months. The grain was surface washed, Soxhlet-extracted with methanol, and the residues determined. A relative constant amount of bound residues (4%), i.e., non-extractable radioactivity, was found 4 months after application and remained constant. More than 97% of the extractable radioactivity in the grain after 6 months was identified as diflubenzuron. When the bound residues were fed to rats, 47% of the administered dose was eliminated via the urine and the remainder via feces within 96 h. Diflubenzuron was the major component in the urine. Adding bound residues to housefly media resulted in a dose-dependent mortality of housefly pupae. Bound residues were biologically active, preventing the emergence of adult houseflies. Supercritical fluid extraction of the bound residues extracted 92% and 96% of the radioactivity associated with grain and feces, respectively. Only diflubenzuron was present in these extracts. The bioavailability and biological activity of bound residues of diflubenzuron have been demonstrated and the identity of the radioactivity was shown to be parent compound. Based on these findings, bound pesticide residues can no longer be ignored or overlooked in the evaluation of pesticide residues and their possible toxicological implications.

Animals↗

PubMed1997

Diflubenzuron tolerance associated with monooxygenase activity in field strain larvae of the Australian sheep blowfly (Diptera:Calliphoridae).

In vitro monooxygenase activity (aldrin epoxidation) in 19 field-collected strains of the Australian sheep blowfly Lucilia cuprina (Wiedemann) varied over a 46-fold range. Activities were significantly correlated with toxicological responses to diflubenzuron and diazinon. Relationships between activity and toxicological response were stronger at the LC95 than at the LC50. Toxicological responses to diflubenzuron and diazinon were significantly related, particularly at the LC95. The slope of diflubenzuron concentration-response lines decreased as enzyme activity increased, suggesting that the proportion of the larval population that can tolerate high rates of diflubenzuron increases with increasing mean enzyme levels. Tolerance levels to diflubenzuron among the field strains (relative to a reference susceptible strain) were up to 10-fold at LC50 and 56-fold at LC95. This tolerance appears to be provided, at least in part, by enhanced larval monooxygenase levels.

Animals↗

PubMed1991

Accumulation of diflubenzuron in bolti fish Orechromis niloticus.

Orechromis niloticus fingerlings were exposed to the insect growth inhibitor diflubenzuron 1-(2,6-Difluorobenzoyl)3-(4-chlorophenyl)urea for 21 days. Diflubenzuron was introduced to the aquariums where fish were maintained at the beginning of the experiment, then its level in water, gills and liver was detected after 1, 7, 14 and 21 days. The fish accumulated diflubenzuron 76 and 99 times greater than the water content when kept in an ambient concentration of 2.5 and 5 mg/l, respectively, indicating a low bioaccumulation potential. Some degradation products of diflubenzuron were found mainly in liver and water.

Animals↗

PubMed1984

Pharmacokinetics of diflubenzuron in two types of chickens.

Pharmacokinetic parameters of [14C]diflubenzuron, N-([(4-chlorophenyl) amino]-carbonyl)-2,6-difluorobenzamide, in White Leghorn (WL) egg-production chickens and Rhode Island Red/Barred Plymouth Rock (RIR/BPR) meat-production chickens after single 1-mg/kg intravenous and single 5-mg/kg oral doses were investigated to explain a breed-related egg residue-level difference (higher in WL chickens) after daily oral administration. Analysis of [14C]diflubenzuron concentration in blood versus time indicated similar two-compartment models for each bird type. [14C]Diflubenzuron elimination half-lives from the blood of WL and RIR/BPR chickens were 14.7 and 8.4 h, respectively. Absorption of [14C]diflubenzuron after a single 5-mg/kg oral dose was both faster and more complete in RIR/BPR chickens. Absorption rate constants were 0.046 h-1 and 0.192 h-1 for WL and RIR/BPR hens, respectively. It is concluded that the breed-related egg residue difference was due to a larger peripheral compartment volume in RIR/BPR hens.

Administration, Oral↗

PubMed1990

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.

Animals↗

PubMed2003

Laboratory and field evaluation of tebufenozide, diflubenzuron, and Bacillus thurengiensis var. kurstaki for suppression of Douglas-fir tussock moth (Orgyia pseudotsugata (McDunnough)) in Idaho: a case study.

The insect growth regulator tebufenozide (MIMIC 2LV) was tested to examine its impact on the Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough) (Lepidoptera: Lymantriidae). Laboratory tests gave an estimated concentration of 1.26 ppm of the compound to achieve 50% population mortality (LC50) for second-instar O. pseudotsugata. At the highest concentration tested, tebufenozide resulted in significant larval mortality within 7 d with an estimated time to 50% population mortality (LT50) of 6.3 d. A field comparison oftebufenozide with diflubenzuron (Dimilin 4L) and Bacillus thurengiensis var. kurstaki (Btk, FORAY 48B) was also conducted. There was no significant difference in larval mortality within field plots that were treated with diflubenzuron (42.4%) or Btk (44.8%). Larval mortality in the tebufenozide-treated plots (56.8%) was also similar to the mortality in the diflubenzuron and Btk treatments. All three treatments resulted in more larval mortality than that measured in untreated controlplots (11.2%). Both tebufenozide and diflubenzuron treatments resulted in significantly more mortality (55.0% and 40.0%, respectively) to larvae-fed treated foliage 3 wk after application than was measured for larvae-fed foliage from untreated trees (11.0%). There was no significant difference among the treatments in the percentage of host trees in the overstory that sustained >25% defoliation, and all three treatments resulted in less defoliation than was measured in the control plots. There was no significant difference among the treatments in the percentage of host trees in the understory that sustained >25% defoliation.

Animals↗

PubMed1980

Diflubenzuron: intestinal absorption and metabolism in the rat.

1. The metabolic fate of the insecticide diflubenzuron was investigated in the rat with radioactively labelled forms of the compound. 2. Intestinal absorption, measured as the sum of urinary and biliary excretion, diminished greatly with increasing dose, from about 50% at 4 mg/kg to about 4% at 900 mg/kg. 3. Excretion was almost complete at 72 h after dosing. At that time up to 4% of a dose was recovered from the carcasses of the rats. No detectable excretion of radioactive CO2 occurred (less than 0.5% of dose). 4. The metabolic pattern in urine and bile was investigated with diflubenzuron labelled with both 3H and 14C. No unchanged compound was detected. About 80% of the metabolites appeared to have the basic diflubenzuron structure intact. Three of these, hydroxylated at either aromatic ring, were identified; they were largely excreted as conjugates in the bile. The remainder, also largely excreted in the bile, constituted very polar material. About 20% of the diflubenzuron underwent scission of the ureido bridge. One scission product, 2,6-difluorobenzoic acid, was largely excreted as such in the urine. Its counterpart, 4-chlorophenylurea, was not present in urine or bile in appreciable quantity; nor was 4-chloroaniline detected.

Animals↗

PubMed1982

The influence of diflubenzuron on several reproductive characteristics in male and female-layer-breed chickens.

The possibility exists for the accidental contamination of feedstuffs used in poultry and livestock feeds with diflubenzuron (Dimilin, TH 6040; N-[[(4-chlorophenyl)amino]-carbonyl]-2, 6-difluorobenzamide), an insect growth regulator. The effect of this insecticide on reproduction in chickens was tested by feeding diflubenzuron at levels of 1, 2.5, 25, and 250 ppm to male and female layer-breed chickens from 1 day of age through a laying cycle. Characteristics measured were egg production, egg weight, eggshell weight, fertility, hatchability, and effects on the progeny. Feeding diflubenzuron at levels up to 250 ppm did not affect the characteristics measured. These results will be useful in evaluating the use of diflubenzuron in the field.

Animals↗

PubMed1996

Evaluation of Methoprene (Altosid) and Diflubenzuron (Dimilin) for control of mosquito breeding in Tezpur (Assam).

Insect growth regulators (IGRs) namely, Isopropyl (E-E)-(RS)-11-methoxy-3,7,11-trimethyldodeca-2, 4-dinoate (Methoprene) and 1-(4-cyclophenyl)-3-(2,6-diflerobenzoyl) urea (Diflubenzuron) were evaluated against mosquito larvae in laboratory as well as in different breeding habitats in Tezpur, Assam. LC90 values of diflubenzuron against Culex quinquefasciatus and Aedes albopictus were 0.0022 and 0.0027 ppm respectively, while it was 0.0027 and 0.0022 ppm respectively in case of methoprene. However, LC50 values of both the IGRs were almost same in case of Ae. albopictus and Cx. quinquefasciatus (varies between 0.0009 and 0.0011 ppm). In case of methoprene, maximum mortality was observed in pupal stage though the exposure was given in all the cases to the III instar larvae. Field trials were conducted in cemented drains, small ponds and ditches. At 0.2 ppm (0.020 kg/ha) both diflubenzuron and methoprene were found to eliminate 92-96 per cent Culex and Anopheles larvae. Methoprene and diflubenzuron were found equally effective for control of mosquito breeding in different breeding habitats and provide better efficacy than conventional larvicides and biocides.

Aedes↗