Cross-Resistance to Imidacloprid in Strains of German Cockroach (Blattella germanica) and House Fly (Musca domestica)

The toxicity of a promising new insecticide, imidacloprid, was evaluated against several susceptible and resistant strains of German cockroach and house fly. Imidacloprid rapidly immobilized German cockroaches followed by a period of about 72 h during which some cockroaches recovered. After 72 h there was no further recovery. Imidacloprid-treated houseflies were immobilized more slowly than treated cockroaches, with the maximum effect observed after 72 h, and there was no recovery. Based upon 72-h LD₅₀ values imidacloprid was moderately toxic to German cockroaches (LD₅₀ values were 6–8 ng mg^-1) and had only low toxicity to house flies (LD₅₀ 140 ng mg^-1). Piperonyl butoxide (PBO) blocked the observed recovery in German cockroaches. PBO also greatly enhanced the 72-h LD₅₀ of imidacloprid from 43- to 59-fold in cockroaches and 86-fold in house flies. Two strains of German cockroach (Baygon-R and Pyr-R) showed >4-fold cross-resistance to imidacloprid. This cross-resistance could not be suppressed by PBO, suggesting that P450 monooxygenase-mediated detoxication is not responsible for this cross-resistance. Variation in the level of synergism observed with PBO (between strains) suggests the ‘basal’ level of monooxygenase-mediated detoxication of imidacloprid is quite variable between strains of German cockroach. The AVER and LPR strains of house fly showed significant cross-resistance to imidacloprid. PBO reduced the level of cross-resistance in AVER from >4·2-fold to 0·5-fold (i.e. the AVER strain LD₅₀ was half that of the susceptible strain when both were treated with PBO), but PBO did not suppress the cross-resistance in LPR. These data suggest monooxygenases are the mechanism responsible for cross-resistance to imidacloprid in AVER, but not in the LPR strain. © of SCI.     

Picrotoxinin receptor in the central nervous system of the American cockroach: Its role in the action of cyclodiene-type insecticides

The nature of the picrotoxinin receptor was studied using the central nervous system (CNS) of the American cockroach. It first was confirmed by using an electrophysiological technique that the abdominal nerve cord of the American cockroach was sensitive to picrotoxinin. By using a $\text{[}{}^3\text{H]α-dihydropicrotoxinin}$ binding test it was determined that the picrotoxinin receptor in CNS of this insect had a higher affinity toward picrotoxinin and heptachlor epoxide than the corresponding receptor in the rat brain. Also, the cockroach brain preparation had a higher percentage of specific binding in the total binding, making this material suitable for receptor studies. By using a sucrose density centrifugation technique, it was determined that the fraction sedimented at the interphase of 1.0 to 1.2 M sucrose at 100,000g contained the highest level of specific binding site. The receptor showed a sensitivity to all insecticidal cyclodienes tested, namely photodieldrin, oxychlordane, endrin, heptachlor epoxide, γ-chlordane, dieldrin, aldrin, heptachlor, and isodrin (expressed in the order of potency). Among four BHC isomers, the γ-isomer showed the highest potency to bind with this receptor.     

Genetic and biochemical mechanisms limiting fipronil toxicity in the LPR strain of house fly,Musca domestica

Fipronil is a new insecticide which exerts its toxic action by interacting with the insect GABA-gated chloride channel. Previous studies have shown that cyclodiene-resistant insects have low to moderate levels of cross-resistance to fipronil, while other resistant strains are usually susceptible. In contrast, we recently found a strain (LPR) of house fly (Musca domestica L) with 15-fold cross-resistance to fipronil that was not associated with cyclodiene resistance. Fipronil cross-resistance in LPR was inherited as an intermediately dominant, autosomal, multigenic trait. [¹⁴C]Fipronil was observed to penetrate into LPR flies more slowly than into susceptible flies. S,S,S-tributylphosphorotrithioate and diethyl maleate pretreatment did not reduce the level of fipronil cross-resistance, while piperonyl butoxide resulted in a slight decrease. These results indicate that decreased penetration and monooxygenase-mediated detoxification may be mechanisms contributing to fipronil cross-resistance in the LPR strain. © 1999 Society of Chemical Industry     

The toxicity of mptp (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) to Periplaneta americana l. and its effects on dopamine in the cerebral ganglia

MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and MPP⁺ (1-methyl-4-phenylpyridinium ion) are potent dopaminergic neurotoxins in mammals. The mammalian toxicity of MPTP depends on its conversion, by monoamine oxidase, to MPP⁺. MPTP is toxic to cockroaches (LD₅₀ 720 μg gm^?1) and the results suggest that MPTP toxicity depends on monoamine oxidase activity at a site outside the nervous system. MPTP depletes dopamine from cockroach cerebral ganglia and MPP⁺ inhibits cockroach mitochondrial respiration. While the biochemistry of MPTP toxicity appears to be the same as in mammals it seems that insects are unable to detoxify MPTP before its action has fatal consequences outside the nervous system.     

Mode of action of β-carboline convulsants on the insect nervous system and their potential as insecticides

Little information is available on the actions of β-carboline convulsants on insect GABA receptors or their potential as insecticides. Accordingly, two compounds (3-ethoxy-β-carboline, 3-EBC; dimethoxy-β-carboline-3-methyl ester, DMCM) were studied for their effects on Drosophila melanogaster larval neuron discharge and also in lethality bioassays on adult female D. melanogaster and adult male Blattella germanica. Recordings of nerve spiking in the isolated larval central nervous system showed that 3-EBC and DMCM inhibited nerve discharge, and this inhibitory effect was not additive with that of GABA, confirming that the inhibition was expressed through an action on the GABA receptor. Nerve blockage induced by β-carbolines could not be reversed by picrotoxinin, indicating that there may exist some overlap or negative allosteric coupling between the picrotoxinin and β-carboline binding sites. DMCM and 3-EBC effectively antagonized the effects of exogenously applied GABA in nerve preparations from insecticide-susceptible larvae. In contrast, preparations from the rdl strain of D. melanogaster, which possesses a GABA receptor that is highly resistant to cyclodienes and related convulsants, were less sensitive to the GABA antagonist effect of DMCM. Neither of the β-carbolines produced any appreciable mortality in insects, even when synergized with piperonyl butoxide or S,S,S-tributyl phosphorotrithioate, The toxicity of the β-carbolines is probably limited by their relatively weak effects on the GABA receptor and perhaps also by pharmacokinetic factors. These considerations, coupled with the cross-resistance observed in cyclodiene-resistant insects, suggest that the currently available β-carbolines are not viable as lead compounds for insecticide screening efforts. © 1997 SCI.     

Repellancy and contact toxicity of clove bud oil and its constituents against German cockroaches,Blatella germanica (Dictyoptera: Blattellidae), under laboratory conditions

Abstract

The German cockroach, Blattella germanica L. (Dictyoptera: Blattellidae), an invasive pest of human habitats, is distributed throughout the world, except in Antarctica. They have developed resistance against chemical pesticides used for the management of their populations. Numerous essential oils and their constituents have been tested; however, the insecticidal activities of clove bud powder, oil, and their constituents have not yet been tested against the German cockroaches. Thus, in this study, clove bud powder, oil, and their major constituents, eugenol and eugenol acetate, were evaluated for their contact toxicity and repellancy against adult German cockroaches under laboratory conditions. The clove bud powder applied at 30?mg/cm² killed 92% of German cockroaches at 6?hours after treatment (HAT). Similarly, clove bud oil, eugenol and eugenol acetate applied at 4.00?ml/cm² provided 95%, 85%, and 87% German cockroach mortality at 24, 6, and 24 HAT, respectively. At 2.0?ml/cm², clove bud oil repelled 80% of German cockroaches within 30?min. In contrast, eugenol and eugenol acetate repelled 85% at 1.0?ml/cm² and 2.5?ml/cm², respectively, at 0.5 HAT. Based on this study, clove bud powder, oil, eugenol, and eugenol acetate could be environmentally friendly tools for the management of German cockroaches.     

Expression and inheritance of nerve insensitivity resistance in larvae of Helicoverpa armigera (Lepidoptera: Noctuidae) from China

Nerve insensitivity resistance to synthetic pyrethroids was detected in a resistant field strain (JSFX-R) of the cotton bollworm, Helicoverpa armigera (Hübner), using a neurophysiological assay in which extracellular spontaneous neuronal activity was measured in response to cis-cypermethrin. The nerve insensitivity mechanism was selected using a combination of toxicological and neurophysiological methods. The third-instar larvae in selected strains of Family-37 and CTR strain expressed a very high resistance to fenvalerate (RF = 2060-fold and 805-fold, respectively) and high cross-resistance to DDT (RF = 1927-fold and 2384-fold, respectively) which was not affected by two metabolic synergists, PBO and DMC. The frequency of nerve-insensitive individuals detected in neurophysiological assays (54, 81 and 100% for JSFX-R strain, and the selected strains Family-43 and Family-37, respectively) was not only positively correlated (R² = 0.968) with the frequency of non-PBO-synergisable resistant individuals detected in toxicological tests (37.5, 62.5 and 90% for JSFX-R strain, Family-43 and Family-37, respectively), but also positively correlated (R² = 0.978) with the frequency of DDT-resistant individuals detected in toxicological tests (40, 67.5 and 93.3% for JSFX-R strain, Family-43 and Family-37, respectively). Analysis of dose–mortality lines to DDT and fenvalerate from F₁ hybrids (R♀ × S♂) indicated that nerve insensitivity resistance to DDT and fenvalerate in the CTR strain was inherited in an incompletely recessive pattern. Degree of dominance (D) was estimated to be −0.66 (± 0.06) (DDT) and −0.26 (± 0.04) (fenvalerate). The dose–mortality curves to DDT in back-cross progeny were strongly suggested, by chi-square analysis, to be fitted with those expected of a one-gene model. Evidence for the co-existence of nerve insensitivity and oxidative metabolic resistance mechanisms within individual H armigera and the effects of their interaction on the expression of resistance to fenvalerate are discussed. © 1999 Society of Chemical Industry     

Resistance to inhibitors of sterol biosynthesis in field isolates or laboratory strains of the eyespot pathogen Pseudocercosporella herpotrichoides

Strains of Pseudocercosporella herpotrichoides collected in France on winter wheat give either fast-growing mycelial colonies with regular margins or slow-growing mycelial colonies with irregular margins. Most of the fastgrowing isolates were sensitive to triadimenol (EC₅₀ below 2mg litre^?1), but some of them were resistant to this inhibitor of sterol C-14 demethylation. In contrast, all the slow-growing strains were highly resistant to triadimenol (EC₅₀ greater than 100 mg litre^?1). This resistance was also expressed in inhibition of germ-tube elongation. Positive cross-resistance was observed between most of the inhibitors of sterol C-14 demethylation, with the exception of some imidazole derivatives (clotrimazole, prochloraz). All the fast-growing strains were tolerant to fenpropimorph and fenpropidin whereas the slow-growing ones were susceptible; the reverse was true with piperalin and tridemorph. All the field isolates were inhibited to the same extent by the inhibitors of squalene-epoxidase, nafifine and terbinafine. Two types of mutant resistant to triadimenol have been induced under laboratory conditions from sensitive fast-growing strains. The most common mutants were resistant to all the inhibitors of sterol C–14 demethylation and also in some conditions to fenpropimorph, tridemorph and the inhibitors of squalene-epoxidase. The other mutants were characterised by a reduced spectrum of cross-resistance between triadimenol and the other inhibitors of sterol biosynthesis. The field isolates and laboratory mutants resistant to triadimenol and propiconazole were also resistant to each of the four enantiomers of these two fungicides.     

Action of avermectin B1a on the leg muscles and the nervous system of the American cockroach

The action of avermectin was studied in the leg muscle and the central nervous system of the American cockroach, Periplanata americana L. Avermectin at a low concentration (10^?7M) causes a failure of the leg muscles to respond to external stimuli within 30 min without affecting the magnitude of contraction. Avermectin was found to stimulate Cl^? uptake by the leg muscles within 4 min at 10^?7M. The threshold concentration to cause such stimulation was on the order of 10^?8M. This stimulatory action could be antagonized by picrotoxinin (10^?4M) and to a lesser extent by bicuculline methiodide (10^?4M). The phenomenon is observable under both Na⁺-free and K⁺-free conditions. It was concluded that the action of avermectin is to open the chloride channel on the plasma membrane. This action of avermectin does not seem to be mediated through GABA, GABA receptors, diazepine receptors, or picrotoxinin receptor in this insect species, and therefore suggests that avermectin directly attacks the chloride channel proper both in the central nervous and the neuromuscular systems.     

Correlation of a resistance-associated Rdl mutation in the German cockroach, Blattella germanica (L), with persistent dieldrin resistance in two Danish field populations

Danish Blattella germanica (L) populations carry the resistance-associated mutation A302S within the Resistance to dieldrin (Rdl) gene. The mutation has remained in field populations long after the discontinuation of dieldrin for cockroach control. The mutation has also persisted in our laboratory strains with high and intermediate frequencies for more than 8 years without selection. The toxicity of dieldrin was tested by topical application to male cockroaches in the susceptible strain DPIL-SUS and two field strains, Zo960302 and Su960304, which were 1270- and 15-fold resistant to dieldrin at LD50. We report the sequencing of exon 7 of the B. germanica Rdl gene and the finding of the putative resistance-associated A302S mutation. We have developed and implemented a PCR-based diagnostic method with the detection of a restriction endonuclease polymorphism, which allows for easy discrimination of susceptible, resistant and heterozygote genotypes. The frequency of the resistance-associate allele A302S was 0.97 and 0.38 in the Zo960302 and Su960304 populations, respectively. The cockroach Rdl A302S allele confers high dieldrin resistance in homozygotes and intermediate resistance in heterozygotes, and its presence is responsible for the persisting dieldrin resistance in Danish populations of B. germanica.     

Excitation of central neurons by dieldrin and picrotoxinin in susceptible and resistant Drosophila melanogaster (meigen)

Neurophysiological studies were used to characterize the resistance mechanism in a new cyclodiene-resistant strain of Drosophila melanogaster. Suction electrode recordings were taken from the peripheral nerves of transected larval central nervous system. Treatment of nerve preparations with 1 mM GABA reduced the spontaneous firing of peripheral nerves. This inhibition was effectively reversed within 10 min by exposing preparations from susceptible insects (Oregon-R wild type) to 10 μM dieldrin. In contrast, 30 min incubations with 10 μM dieldrin had no effect on preparations from resistant individuals. At 10 μM, picrotoxinin was also effective in antagonizing the action of GABA in susceptible nerve preparations. In recordings from resistant insects (n = 3), picrotoxinin displayed either no antagonism of GABA-dependent inhibition, weak antagonism of GABA, or hyperexcitation indistinguishable from those of susceptible preparations. These results demonstrate that cyclodiene resistance in the Maryland strain of D. melanogaster is present at the level of the nerve, and that the resistance extends to picrotoxinin, albeit at a reduced level. The possible role of an altered GABA receptor in this resistance is discussed.     

Effect of thiamethoxam on cockroach locomotor activity is associated with its metabolite clothianidin

BACKROUND: In the present study, the effect of thiamethoxam and clothianidin on the locomotor activity of American cockroach, Periplaneta americana (L.), was evaluated. Because it has been proposed that thiamethoxam is metabolised to clothianidin, high‐performance liquid chromatography coupled with mass spectrometry was used to evaluate the amount of clothianidin on thiamethoxam‐treated cockroaches. RESULTS: One hour after neonicotinoid treatment, the time spent in the open‐field‐like apparatus significantly increased, suggesting a decrease in locomotor activity. The percentage of cockroaches displaying locomotor activity was significantly reduced 1 h after haemolymph application of 1 nmol g^?1 neonicotinoid, while no significant effect was found after topical and oral administration. However, at 24 and 48 h, all neonicotinoids were able to reduce locomotor activity, depending on their concentrations and the way they were applied. Interestingly, it was found that thiamethoxam was converted to clothianidin 1 h after application, but the amount of clothianidin did not rise proportionately to thiamethoxam, especially after oral administration. CONCLUSION: The data suggest that the effect of thiamethoxam on cockroach locomotor activity is due in part to clothianidin action because (1) thiamethoxam levels remained persistent 48 h after application and (2) the amount of clothianidin in cockroach tissues was consistent with the toxicity of thiamethoxam. Copyright © 2010 Society of Chemical Industry     

Cholinergic receptors of the central nervous system of insects

Concentrated particulate preparations were made from housefly heads and the nerve cords of the American and Madagascar cockroaches. Macromolecules present in these preparations bound ³H-nicotine reversibly and with high affinities (3, 1.1, and 1.5 μM, respectively). Binding of ACh to the macromolecules in the preparation of houseflies and Madagascar cockroach was determined by inhibition of ³H-nicotine binding, and was found to be of much lower affinity than that of nicotine.There was a 2 × purification of the nicotine-binding macromolecules in this particulate preparation of housefly heads as compared to an earlier preparation of supernatant of 100,000g. Nicotine binding to this particulate preparation was blocked also by d-tubocurarine and atropine demonstrating the nicotinic and muscarinic nature of these nicotine-binding macromolecules. Prior exposure of the preparation to trypsin and chymotrypsin reduced nicotine binding by 58 and 68%, respectively.The relationship of these nicotine and ACh binding macromolecules to ACh-receptors is discussed.     

Effects of DDT on the cockroach nervous system at three temperatures

Some effects of DDT on the cockroach nervous system have been correlated with poisoning symptoms, using free-walking cockroaches with implanted electrodes. Experiments at 16.5°C and 32°C used LD₉₅ doses and at 25°C, an estimated LD₉₅. DDT had excitant actions on each nerve studied; cercal afferent and efferent neurones, and abdominal interneurones. The effects on the central nervous system became more marked as temperature was reduced, despite the smaller quantity of DDT employed, but the excitant actions on the peripheral nervous system were not quantified. It is suggested that the effects of DDT on the cockroach nervous system could account for the negative temperature coefficient of toxicity of DDT.     

Biochemical mechanisms conferring cross-resistance between tebufenozide and abamectin in Plutella xylostella

Experiments have been carried out to confirm the cross-resistance between abamectin and tebufenozide in Plutella xylostella and demonstrate its mechanism. The results showed that the resistant strain of P. xylostella selected by tebufenozide (RF 99.38) really showed high cross-resistance to abamectin (RF 29.25). When this strain was subjected to resistance decaying treatment, breeding without contacting any insecticides, and abamectin resistance selection for 20 generations, the former resulted in decrease of its resistance to both tebufenozide and abamectin to about one third of the original (RF 35.03 and 11.67, respectively), and the later enhanced its resistance to abamectin dramatically (RF 303.77), but not to tebufenozide(RF 50.04). PBO showed high synergism to abamectin (SR 2.11-12.23), and the synergism ratio positively related to the resistance level among different strains. Enzyme analysis also proved that the activity of cytochrome P450 monooxygenase (MFO) was notable enhanced in the strains resistant to both tebufenozide and abamectin (1.71- to 3.01-fold). Based on discussion, it was concluded that tebufenozide selection could resulted in significant cross-resistance of P. xylostella to abamectin. The major mechanism for the cross-resistance should be the enhancement of MFO activity. For resistance management, tebufenozide and abamectin would not recommend for rotational use.     

The effects of dieldrin and isomeric aldrin diols on synaptic transmission in the American cockroach and their relevance to the dieldrin poisoning syndrome

Dieldrin and two of its metabolites, 6,7-trans-dihydroaldrindiol, and 6,7-cis-dihydroaldrindiol, were studied with regard to their toxicity to the American cockroach, effects on ganglia of the ventral nerve cord, and penetration into the ventral nerve cord of poisoned cockroaches. An approximate LD₅₀ for injected doses of dieldrin was 0.45 mg/kg. After injection at 115 mg/kg, the trans isomer of aldrin diol caused about 70%, and the cis isomer about 50% mortality. Injected doses of 40 mg/kg of the three compounds appeared in the ventral nerve cord to the extent of 0.13–0.26% of the doses. Dieldrin was more potent, but slower acting than the diols in causing synaptic after-discharge and elevated spontaneous activity in isolated nerve cords. The results are discussed in relation to other studies on these compounds. It was concluded that, in the American cockroach, dieldrin, rather than either of the diols, is the insecticidal agent in dieldrin poisoning, and that metabolic conversion of dieldrin to the cis and/or trans aldrindiol constitutes a detoxification.     

The in vitro degradation of [14C]malathion by enzymatic extracts from resistant and susceptible strains of Drosophila melanogaster

Enzyme preparations from Drosophila melanogaster flies degraded [¹⁴C]malathion to α- and β-malathion monoacids and, hence, were considered to contain malathion carboxylesterase (ME) activity. Although ME- activity was stable during preincubation in the absence of malathion, it decreased dramatically during the course of the reaction, and could not be completely recovered by Sephadex G-25 chromatography. Furthermore, the protein fraction after chromatography still contained ¹⁴C, suggesting that the enzyme had become inhibited by a bound, ¹⁴C-labeled derivative. Extracts from a resistant (malathion-selected), an intermediate control, and the susceptible Canton S strains of D. melanogaster differed in the lability of ME activity during the reaction. This difference was partly attributed to the production of small amounts of malaoxon (2–8%) by the extracts from the more resistant strains. No consistent strain differences were found when the rate of malathion degradation was measured during the first minute of reaction, either with or without a microsomal oxidase inhibitor (metyrapone) present. These results, together with the cross-resistance of the malathion-selected strain to other insecticides and the lack of a synergistic effect of two carboxylesterase inhibitors (triphenyl phosphate and S,S,S-tributylphosphorotrithioate) suggested that malathion carboxylesterase does not contribute significantly to the observed differences in malathion resistance between strains.     

The mode of action and neurotoxicity of mirex,chlordecone, and four hydrogenated mirex analogs

The toxicity and neurological effects of mirex, chlordecone, and four hydrogenated mirex analogs were evaluated on the American cockroach. The severity of poisoning symptoms correlated with the ability of each compound to increase spontaneous activity and prolong synaptic afterdischarge in ganglia of the ventral nerve cord. Afterdischarge across the metathoracic ganglion was consistent with a characteristic wing splaying symptom in mirex-poisoned cockroaches. The actions of hemicholinium-3 and nicotine on nerve cords from mirex-poisoned cockroaches are described and are consistent with a hypothesis that the increased spontaneous activity and afterdischarge are the result of enhanced transmitter release in ganglia of poisoned animals.     

Mode of action of the plant-derived silphinenes on insect and mammalian GABAA receptor/chloride channel complex

The silphinenes are tricyclic sesquiterpenes that have antifeedant and toxic effects in insects and structural similarity to the known GABA antagonist, picrotoxinin. In murine synaptoneurosomes, silphinenes block GABA-stimulated influx of ³⁶Cl⁻ with EC₅₀s in the range of 10-30 μM. In insects, silphinenes were tested in neurophysiological recordings of central neurons from third instar Drosophila melanogaster larvae. Silphinenes reversed the blockage of neuronal firing induced by GABA, but had little effect below 100 μM. The structure-activity profile observed in the murine chloride flux assay was also observed in the larval neurophysiological assay, indicating little selectivity for the silphinenes. A reference silphinene was equally active on nerve preparations from the rdl strain of D. melanogaster, which is resistant to channel-blocking antagonists via an altered GABA receptor. This latter finding suggests that silphinenes interact with the insect GABA receptor in a manner somewhat different from PTX, and that rdl resistance in the field may have little effect on silphinene efficacy.     

Dieldrin transport in the insect: an examination of Gerolt's hypothesis

[¹⁴C]-Dieldrin was detected in the hemolymph of adult male Periplaneta americana and P. brunnea 2.5 hr after an acetone solution of radiodieldrin (RD) was applied to the pronotum. Sephadex thin-layer gel filtration (TLG) of cell-free hemolymph (HL) from cockroaches to which RD was applied, and TLG of HL to which RD was added directly, indicated that dieldrin binds to a protein (s) of ca. 18,900 mol wt and two groups of proteins of mol wt ≥ 160,000. The capacity of Periplaneta HL for RD at 22°C was to at least 57 μM, but the highest concentration of RD detected in HL after topical application was 29.9 μM. The hemocytes contained about 37% of the dieldrin in whole cockroach hemolymph. When isolated cockroach legs were perfused with HL containing protein-bound RD, autoradiography of the dissected legs revealed ¹⁴C counts in the tissues. These findings are consistent with the translocation of topical dieldrin by hemolymph, but do not eliminate the possibility of translocation via the tracheal system.