Effect of binary combination of some plant-derived molluscicides with MGK-264 or piperonyl butoxide on the reproduction of the snail Lymnaea acuminata

The effects of sub-lethal treatments (20 and 60% of 24-h LC(50)) with plant-derived molluscicides Annona squamosa, acetogenins, Argemone mexicana seed and protopine, in combination (1 + 5) with MGK-264 (ENT 8184) or piperonyl butoxide on the reproduction of Lymnaea acuminata has been studied. The plant-derived molluscicides and their active molluscicidal components, protopine and acetogenins, in combination with ENT 8184 or piperonyl butoxide caused a significant reduction in the fecundity, hatchability and survival of young snails. Combination of A squamosa seed powder with piperonyl butoxide was very effective as it caused a complete arrest of snail fecundity within 24 h of treatment. Removal of the snails to fresh water after the 96-h treatments caused a significant recovery in the fecundity of L acuminata.     

Antagonism of iprodione toxicity to Botrytis cinerea by mixed function oxidase inhibitors

The fungitoxicity of iprodione to a sensitive strain of Botrytis cinerea was antagonised by a variety of cytochrome P-450 mixed function oxidase inhibitors. Piperonyl butoxide, metyrapone and N-(2-ethylhexyl)-8,9,10-trinorborn-5-ene-2,3-dicarboximide (MGK-264) at non-fungitoxic concentrations were strongly antagonistic, whereas sesamex, nuarimol, fenarimol, etaconazole and 6-nitro or 6-methoxy 1,2,3-benzothiadiazole were moderately antagonistic. Phenobarbital and 2-diethylaminoethyl 2,2-diphenylvalerate (SKF 525-A) were slightly antagonistic. The results suggest that fungitoxicity of iprodione may be dependent on an activation catalysed by a cytochrome P-450 mixed function oxidase.     

Genetic and biochemical studies of resistance to permethrin in a pyrethroid-resistant strain of the housefly (Musca domestica L.)

One or more weak factors of resistance on autosome 2, and barely detectable resistance on autosome 3, confer moderate resistance to several pyrethroids (5–13-fold) in the field-collected Ipswich strain of houseflies. In these flies, which unlike other pyrethroid-resistant strains lack kdr or super-kdr, pyrethroid resistance probably developed in response to prolonged treatment of buildings for animals with pyrethrins synergised with piperonyl butoxide. Substrains, isolated genetically from Ipswich flies and with resistance only on autosome 2, degraded permethrin more rapidly than susceptible flies and produced larger amounts of very polar metabolites. In this, they differed from flies with kdr or super-kdr which resembled susceptible flies in their metabolism of permethrin. NIA 16388 (propyl prop-2-ynyl phenylphosphonate) was a better synergist and reduced the metabolism of permethrin more than piperonyl butoxide in both the susceptible and resistant insects. The slight increase in synergism and minimal decrease in metabolism when piperonyl butoxide was applied with NIA 16388 indicated that the latter also inhibited detoxication that was sensitive to piperonyl butoxide.     

Laboratory studies on the mechanisms of resistance to permethrin in a field-selected strain of house flies

Enhanced oxidative metabolism appeared to be a major factor involved in resistance to permethrin in a field strain of house flies, selected with permethrin over 4 years. This was shown in the 7.8-fold synergism by piperonyl butoxide which reduced the resistance ratio from 97 to 15. The rate of permethrin detoxication was significantly higher (P=0.05) in the resistant flies compared with a susceptible strain or resistant flies pretreated with piperonyl butoxide. The esterase inhibitor S,S,S-tributyl phosphorotrithioate did not reduce the level of resistance to permethrin in the resistant strain, although some hydrolytic metabolism was apparent. Rates of penetration were similar in susceptible and resistant flies and in resistant flies pre-treated with piperonyl butoxide. A minor unidentified resistance factor, possibly reduced sensitivity of the nervous system, may also have been present in the resistant strain.     

Diazinon poisoning in large white butterfly larvae and the influence of sesamex and piperonyl butoxide

The toxicity of diazinon and diazoxon to fourth instar Pieris brassicae larvae was determined, with or without modifying chemicals. Piperonyl butoxide and sesamex antagonised diazinon but synergised diazoxon. The penetration, excretion and internal concentration of diazinon were measured following topical application. Penetration of diazinon followed first order kinetics and was considerably slower after pretreatment with sesamex and piperonyl butoxide. Pretreatment with piperonyl butoxide increased the internal concentration of diazinon, but the onset of symptoms of poisoning was delayed, presumably because of inhibition of diazinon activation.     

Development of resistance to pyrethroids in insects resistant to other insecticides

Resistance to pyrethroids in insects is rare, but its recent rapid development in the field suggests that this resistance may be facilitated by previous exposure to or by resistance to insecticides of unrelated groups. To test this houseflies of strain 49_r2b, originally resistant to dimethoate in the field, were selected eight times during ten generations with either pyrethrum extract or bioresmethrin with or without piperonyl butoxide or with dimethoate. Selecting with any of the pyrethroids led to resistance to these insecticides and in particular to pyrethrum/piperonyl butoxide. Selecting with pyrethrum/piperonyl butoxide resulted in strongest resistance to the pyrethroids tested, whereas selecting with bioresmethrin/piperonyl butoxide resulted in least resistance. These results show that dimethoate-resistant flies selected with pyrethroids can readily develop resistance to these insecticides, but development of resistance can be minimised by using bioresmethrin/piperonyl butoxide. The implications of these findings on the sequential use of insecticides are discussed.     

Organophosphorothioates and synergised synthetic pyrethroids as grain protectants on bulk wheat

Organophosphorothioates and synergised synthetic pyrethroids were used in duplicate field trials carried out on bulk wheat in commercial silos in Queensland and New South Wales. Laboratory bioassays using malathion-resistant strains of insects were carried out on samples of treated grain at intervals over 9 months. These established that all treatments were generally effective. Deltamethrin (2 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1), fenitrothion (12 mg kg^?1)+ fenvalerate (1 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1), fenitrothion (12 mg kg^?1)+ phenothrin (2 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1) and pirimiphos-methyl (4 mg kg^?1)+ permethrin (1 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1) controlled common field strains of Sitophilus oryzae (L.) and Rhyzopertha dominica (F.). Against a highly resistant strain of S. oryzae, deltamethrin (2 mg kg^?1)+ piperonyl butoxide (8 mg kg^?1) was superior to the remaining treatments. All treatment combinations completely prevented progeny production in Tribolium castaneum (Herbst), T. confusum Jacquelin du Val and in Ephestia cautella (Walker). Residues of deltamethrin, fenvalerate, permethrin and phenothrin were determined and shown to be highly persistent on stored wheat. During milling, residues accumulated in the bran fractions and were reduced in white flour. They were not significantly reduced during baking.     

Effects of the synergist piperonyl butoxide on metabolism of pesticides in green sunfish

The effects of piperonyl butoxide on metabolism of ¹⁴C-labeled methoxychlor, aldrin, and trifluralin were investigated in green sunfish, Lepomis cyanellus. Piperonyl butoxide inhibited epoxidation of aldrin to dieldrin, O-dealkylation of methoxychlor, and N-dealkylation of trifluralin, resulting in higher levels of total radioactivity in animals exposed to the combination compared to those exposed to pesticide alone. Where piperonyl butoxide was present a greater proportion of the total radioactivity in the fish extract occurred as parent compound compared to metabolites than in fish exposed to pesticide alone. After 16 days of exposure piperonyl butoxide increased the proportion of parent compound eight times for methoxychlor, 17 times for aldrin, and 15 times for trifluralin.     

Pharmacokinetics of Intravenous Fenvalerate in Cattle Treated Topically with a Low Dose of Piperonyl Butoxide

Experiments were conducted to identify pharmacokinetic interactions between topically applied piperonyl butoxide and intravenous fenvalerate in cattle (Angus steers). Intact fenvalerate in plasma was derivatized by condensation with acetone and measured by negative chemical ionization gas chromatography/mass spectrometry. Noncompartmental pharmacokinetic analyses indicated that the elimination-phase rate constant (β, 0·00069 (±0·00006) min^-1), mean residence time (172 (±14) min), systemic clearance (10·4 (±0·7) ml min^-1 kg^-1) or volume at steady state (1800 (±230) ml kg^-1) were not changed (P>0·05) after topical application of a low dose of piperonyl butoxide. These data indicate that topical application of a low dose of the metabolic synergist piperonyl butoxide would not be expected to modify the in-vivo disposition of fenvalerate in cattle. © of SCI.     

The status and development of insecticide resistance in Danish populations of the housefly Musca domestica L

Samples of housefly (Musca domestica) field populations were collected from Danish livestock farms in 1997. The tolerance of the first‐generation offspring was determined for a number of insecticides. Dose‐response values were obtained by topical application for the pyrethroids bioresmethrin and pyrethrum, both synergised with piperonyl butoxide, and the organophosphate dimethoate. The organophosphates azamethiphos and propetamphos and the carbamate methomyl were tested in discriminating dose feeding bioassays. Resistance was low to moderate in most of the populations for most of the compounds tested, but this study also revealed the existence of high resistance to pyrethroid, organophosphate and carbamate insecticides in some populations. The resistance factors at LD₅₀ for bioresmethrin/piperonyl butoxide ranged between 2 and 98, and for pyrethrum/piperonyl butoxide between 2 and 29. Our results indicate that pyrethroid resistance in Denmark is increasing, since four of the 21 farms showed more than 100‐fold resistance at LD₉₅, a level of resistance only observed once before. Resistance factors at LD₅₀ for dimethoate ranged from 9 to 100, and showed two distinct trends: populations with either decreasing or increasing resistance. Resistance to azamethiphos was found to be widespread and high. Although two strains with high methomyl and propetamphos resistance were observed, methomyl and propetamphos resistance is moderate and appears not to be increasing. © 2001 Society of Chemical Industry     

Organophosphorus and synergised synthetic pyrethroid insecticides as grain protectants for stored sorghum

A field experiment was carried out on bulk sorghum stored for 26 weeks in concrete silos in South Queensland. No natural infestation occurred. Laboratory bioassays of treated grain, in which malathion-resistant strains of insects were added to grain samples, indicated that all the treatments were generally effective. Deltamethrin (2mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹), fenitrothion (12mg kg⁻¹)+fenvalerate (1 mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹), and fenitrothion (12mg kg⁻¹)+phenothrin (2mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹) controlled typical malathion-resistant strains of Sitophilus oryzae (L.), Rhyzopertha dominica (F.), Tribolium castaneum (Herbst) and Ephestia cautella (Walker). Pirimiphos-methyl (6mg kg⁻¹)+permethrin (1mg kg⁻¹)+piperonyl butoxide (8mg kg⁻¹) allowed some survival of adults and progeny production by S. oryzae after 12 weeks, and by one strain of R. dominica throughout. Chemical assays established that the residues and rates of breakdown of these grain protectants on sorghum conformed to the general pattern on other cereal grains. Residues at the conclusion of the experiment were below the individual Maximum Residue Limits recommended by the Codex Alimentarius Commission.     

The effect of single, binary, and tertiary combination of few plant derived molluscicides alone or in combination with synergist on different enzymes in the nervous tissues of the freshwater snail Lymnaea (Radix) acuminata (Lamark)

The effect of single, binary, and tertiary combination of few plant derived molluscicides alone or in combination with synergist on different enzymes (acetylcholinesterase—AChE, lactic dehydrogenase—LDH, and acid/alkaline phosphatase—ACP/ALP in the nervous tissue of the freshwater snail Lymnaea acuminata were studied. Sublethal in vivo 24 h exposure to 40 and 80% of LC₅₀ of Azadirachta indica oil (AI), oleoresin of Zingiber officinale (OL), Cedrus deodara oil (CD), Allium sativum (AS), and Polianthes tuberosa (PT) bulb powder singly, their binary combination of AI + OL, AS + CD, AS + PT, CD + OL, CD + PT, OL + PT, and tertiary combination of these binary combinations with the synergist piperonyl butoxide (PB) or MGK-264 significantly altered the activity of these enzymes. Tertiary combination with PB or MGK was very effective. Combination of CD + PT + MGK was more effective against AChE whereas, the combination of CD + OL + PB, CD + AS + PB, and CD + PT + PB were more effective against LDH, ACP, and ALP, respectively.     

Disposition and metabolism of [14C]chlorpyrifos in the black imported fire ant, Solenopsis richteri Forel

The short-term disposition and metabolism of topically administered [¹⁴C]chlorpyrifos was assessed in the black imported fire ant (Solenopsis richteri Forel) in the presence and absence of the mixed-function oxidase inhibitor piperonyl butoxide. Chlorpyrifos is readily absorbed into an internal organosoluble fraction which was quickly converted into a water-soluble fraction. The radioactivity was slowly excreted over a 24-hr period. Piperonyl butoxide slowed the conversion of the internal organosoluble radioactivity to the water-soluble fraction. Thin-layer chromatography indicated that piperonyl butoxide slowed the conversion of chlorpyrifos to material remaining at the origin, presumably water-soluble metabolites. The results of acid hydrolysis studies indicated that the water-soluble radioactivity was comprised mainly of conjugates. Although very little chlorpyrifos oxon was recovered in the metabolism experiments, in vitro studies on fire and head homogenates showed the compound to be an extremely potent anticholinesterase, with an I₅₀ of 4.6 × 10^?10M, while a major metabolite, 3,5,6-trichloropyridinol, was an ineffective acetylcholinesterase inhibitor.     

Toxicity of chlordimeform and amitraz to the egyptian cotton leafworm (Spodoptera littoralis) and the tobacco budworm (Heliothis virescens)

The relative toxicity (μg a.i. g^?1 body wt) of the formamidine insecticide chlordimeform (CDM) and the triazapentadiene insecticide amitraz was examined in two species of noctuid moth Spodoptera littoralis and Heliothis virescens. When applied topically, there was an unexpected and marked difference in the toxicity of CDM base and its hydrochloride to adults of both species, the salt being appreciably more toxic. For H. virescens at least, this difference in toxicity could not be explained by differences in penetration. This trend was reversed for larval instars of S. littoralis; while there was relatively little difference in the toxicity of the base to adult and larval stages, the salt was at least 1000-fold more toxic to adults than to larvae. N¹-Demethylchlordimeform (DCDM) was the only metabolite of CDM to show biological activity against either species, but was much less toxic than the parent compound. Amitraz was far less toxic than either CDM or DCDM; like the CDM salt, it appeared to be more toxic to adult than larval stages of S. littoralis. Application of piperonyl butoxide significantly increased the toxicity of the CDM salt, DCDM and amitraz to adult H. virescens, the synergist being particularly effective with DCDM and amitraz. In contrast, piperonyl butoxide had no significant effect on the toxicity of DCDM, and slightly antagonised the toxicity of DCDM to fourth-instar larvae of S. littoralis.     

Abamectin resistance and synergism in Brazilian populations of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

Failures in the control of the tomato leafminer Tuta absoluta (Meyrick) by means of abamectin in Brazil, and a recent report of abamectin resistance in Brazilian populations of this pest species, led to the investigation of the possible involvement of detoxification enzymes using insecticide synergists. Resistance to abamectin was observed in all populations when compared with the standard susceptible population, with resistance ratios ranging from 5.2- to 9.4-fold. Piperonyl butoxide was the most efficient synergist with abamectin synergism ratios ranging from 3.0- to 5.3-fold and providing significant resistance suppression, but complete suppression of abamectin resistance was only obtained in one population of T. absoluta . Triphenylphosphate was an abamectin synergist which was not as efficient as piperonyl butoxide, but it provided complete suppression of abamectin resistance in four of the six resistant populations studied, suggesting a major involvement of esterases as an abamectin resistance mechanism in these populations. The importance of cytochrome P450, inhibited by piperonyl butoxide, seems secondary to esterases. Diethyl maleate also synergized abamectin in nearly all populations, but provided only partial suppression of abamectin resistance in the leafminer populations studied. Therefore, glutathione-S-transferases seem to be of minor importance as an abamectin resistance mechanism in Brazilian populations of T. absoluta .     

Toxicity to the snail Limnaea acuminata of plant‐derived molluscicides in combination with synergists

The effects of combinations of plant‐derived molluscicides with piperonyl butoxide (PB) or ENT 8184 (MGK‐264) were studied on different enzyme activities and biogenic amine levels in the nervous tissue of Limnaea acuminata. 24‐h in vivo exposure of the nervous tissue of L acuminata to 40% and 80% of the 24‐h LC₅₀ of the plant‐derived molluscicides Azadirachta indica oil, Allium sativum powder and oleoresin of Zingiber officinale rhizome and their active molluscicidal components azadirachtin, allicin and [6]‐gingerol, alone or in combination (1 + 5) with PB or ENT 8184, caused a significant reduction in the activity of acetylcholinesterase, lactic dehydrogenase, acid and alkaline phosphatases and sodium‐potassium ATPase. There was a significant increase in the activity of succinic dehydrogenase. In vivo exposure for 24 h to sub‐lethal concentrations of azadirachtin, allicin and [6]‐gingerol, singly and with PB or ENT 8184, significantly altered the dopamine and 5‐hydroxytryptamine levels in the nervous tissue of L acuminata. It is concluded that these active moieties singly or with PB or ENT 8184 adversely affect all known neurotransmission mechanisms in the snail, either separately or through a complex interaction between the different neurotransmitters. © 2000 Society of Chemical Industry     

A new resistance to pyrethroids in tribolium castaneum (herbst)

The characteristics of a new high-level, field-derived resistance to pyrethroids in Tribolium castaneum (Herbst) were investigated using impregnated-paper and treated-grain assays. Piperonyl butoxide almost completely suppressed the resistance, suggesting that the major resistance mechanism was microsomal oxidation. Resistance extended to all pyrethroids tested and to carbaryl but not to organophosphorus insecticides or to methoprene. Resistance was strongest against α—CN phenoxybenzyl cyclopropanecarboxylate pyrethroids and was correlated with structural modifications of the pyrethroid molecule, results also consistent with oxidative resistance. This resistance will ultimately result in failures to control T. castaneum if pyrethroids, such as deltamethrin, cypermethrin or cyfluthrin, are used in the field, even if they are synergised with piperonyl butoxide. The resistance does not jeopardise organophosphorus materials (e.g. fenitrothion, chlorpyrifos-methyl, pirimiphos-methyl, methacrifos) or methoprene.     

Structure—activity relationship for some substituted dialkyl vinyl phosphates

The biological activity against the house fly, Musca domestica L., is reported for a series of dialkyl 2-bromo-1-(2,4-dichlorophenyl)vinyl phosphates. Maximum activity and the lowest degree of synergism with piperonyl butoxide were found with the dimethyl ester. Good activity was also shown by the diethyl ester. Both these compounds, used at the same dose, inhibited fly-head acetylcholinesterase. Compounds with longer alkyl chains were less effective and did not inhibit acetylcholinesterase.     

Comparative modification of insecticide-resistance spectrum of Culex pipiens fatigans wied. By selection with temephos and temephos/synergist combinations

The evolution of strong organophosphorus multiresistance, suppressible by S,S,S-tributyl phosphorotrithioate (TBPT), in a California strain of Culex pipiens fatigans was examined by further selection with temephos, alone and in combination with the synergists TBPT or piperonyl butoxide (PB). Selection by temephos and temephos + PB increased resistance to higher levels. However, selection by temephos + TBPT virtually abolished TBPT-suppressible resistance while preventing the emergence of significant alternative resistance mechanisms. The phenomenon of synergism may enable the extended use of an insecticide where alternative resistance mechanisms are either absent or of low efficiency in the target population.     

Insecticidal activity of synthetic 2-carboxylbenzofurans and their coumarin precursors

Several 2-carboxylbenzofurans and their coumarin precursors, compounds 1 – 6 , and the novel compound 7 were synthesized and their insecticidal activity studied using adult sweet potato weevils (Cylas formicarius elegantulus (Summer)) at 24 μg, 48 μg and 72 μg per insect in 0.5 ml litre^?1 piperonyl butoxide (PPB) in acetone. The order of toxicity of the compounds as judged by the percentage mortality at 24 μg per insect at 48 h was 2 (100%) > 6 (95%) > 7 (85%) > 4 (75%)) > 3 (65%) > 1 (60%) > 5 (45%) > piperonyl butoxide (0.0%). Compound 2 was equitoxic to 24 μg of technical grade dimethoate. When administered in acetone alone, however, the compounds were only moderately active (i.e. > 120 μg per insect was required for 60% mortality at 48 h). The test compounds were more active at lower doses (48–72 μg per insect) when dissolved in dimethylsulfoxide or in an oil extract obtained from the fruit of Blighia sapida Koenig.