Addition Of Piperonyl Butoxide Research Articles

Characterization of acaricide resistance in Rhipicephalus sanguineus (latreille) (Acari: Ixodidae) collected from the Corozal Army Veterinary Quarantine Center, Panama.

Rhipicephalus sanguineus (Latreille) were collected from the Corozal Army Veterinary Quarantine Center in Panama and characterized for resistance to five classes of acaricides. These ticks were highly resistant to permethrin, DDT, and coumaphos; moderately resistant to amitraz; and not resistant to fipronil when compared with susceptible strains. Resistance to both permethrin and DDT may result from a mutation of the sodium channel. However, synergist studies indicate that enzyme activity is involved. The LC50 estimate for permethrin was lowered further in the Panamanian strain then in susceptible strains with the addition of triphenylphosphate (TPP), but not with the addition ofpiperonyl butoxide (PBO). This suggests that esterases and not oxidases are responsible for at least some pyrethroid resistance. Elevated esterase activity and its inhibition by TPP were confirmed by native gel electrophoresis. The LC50 estimate obtained for coumaphos in the Panamanian strain was not lowered further than what was observed for susceptible strains by the addition of TPP or PBO. This indicates that enzyme activity might not be involved in coumaphos resistance. Resistance to amitraz was measured through a modification of the Food and Agriculture Organization Larval Packet Test. All tick strains were found to be susceptible to fipronil.

In vitro Metabolism of Flupyrazofos to Plutella xylostella (Lepidoptera: Yponomeutidae) and Spodoptera exigua (Lepidoptera: Noctuidae)

In vitro metabolism study was conducted to observe the role of enzymes and its kind responsible for tolerance in metabolism of flupyrazofos to Diamond backmoth (DBM), Plutella xylostella as a susceptible insect and Beet armyworm (BAW), Spodoptera exigua as a tolerance insect. The results indicated that there were some differences between the DBM (LD 50, 0.54 ppm) and BAW (LD 50, >2,000 ppm). In the microsomal fractions, the 4th instar BAW larvae metabolized almost the same amount (about 38%) of flupyrazofos with or without NADPH, but it increased the amount of flupyrazol in the 3rd instar larvae of DBM. Flupyrazofos-oxon was slightly increased with the addition of NADPH in both species. With the addition of piperonyl butoxide (PB) or Iprobenfos (IBP), the amount of flupyrazol was decreased to one third of flupyrazol produced by NADPH in BAW and one fourth of flupyrazol produced by NADPH in DBM. Some effects of inhibitors, PB and IBP, and co-factor, NADPH, were showed when flupyrazofos was metabolized with or without them. This means that esterase and oxidase are responsible for the tolerance mechanism of flupyrazofos in DBM and BAW.

Cypermethrin pour-on synergized with piperonyl butoxide: effects on Haematobia irritans (Diptera: Muscidae) natural populations resistant to cypermethrin

Development of pyrethroid resistance in Haematobia irritans in Santa Fe province, Argentina, resulted in an increased use of pyrethroid insecticides, probably due to lack of suitable alternative treatments. We explored the efficacy of mixtures of cypermethrin and piperonyl butoxide (PBO) against pyrethroid-resistant H. irritans. Groups of 25 Holstein cows each, naturally infested with cypermethrin resistant H. irritans were assigned to treated or control groups in April, September, October and December 1997. Cattle in treated groups were medicated with pour-on oil formulations of 5% cypermethrin (dose = 4 mg per kg of body weight) with 5% or 10% PBO in April, and with a mixture containing 5% of both components thereafter. Efficacy was tested for 21 days after treatment. A treatment of 5% cypermethrin pour-on without PBO was evaluated in October 1997. Samples of horn flies were obtained before September, October and December treatments and exposed for 2 h to filter papers impregnated with different cypermethrin concentrations to determine the 50% lethal concentration (LC50). No difference in efficacy was found between cypermethrin pour-on formulations with 5% or 10% of PBO (more than 94% efficacy on day 21 after treatment). Efficacy of 5% cypermethrin–5% PBO mixture decreased rapidly in the successive treatments (less than 40% efficacy was observed on day 21 after the December treatment), and the period after treatment with an efficacy higher than 95% was 14 days for the treatment carried out in April, 10 days in September; 7 days for the treatment performed in October and 4 days for the December treatment. The LC50 of cypermethrin was 36.6 μg per cm 2 in September and increased to 116.6 and 226.1μg per cm 2 in October and December, respectively. It is concluded that the addition of PBO to cypermethrin did not provide a treatment that would give a long term control of pyrethroid resistant-horn flies.

Toxicity of Insecticides and Metabolism of Deltamethrin in Helicoverpa assulta Guenéee and Spodoptera litura Fabricius

This experiment was carried out to evaluate the effects of synergists on toxicity of deltamethrin and to investigate the pharmacokinetics of deltamethrin in Helicoverpa assulta Guenéee and Spodoptera litura Fabricius. Susceptibilities of H. assulta and Haman-collected S. litura to 7 insecticides revealed different responses between the 2 species. The different susceptibility of the 2 species to deltamethrin was correlated with the differences in the penetration and metabolism. Larvae of H. assulta pretreated with synergists (piperonyl butoxide (PB), S-benzyl-O, O-diisopropyl phosphorothioate (IBP), and diethyl maleate (DM) were more sensitive to deltamethrin, with the highest synergism ratio (SR = 6.8) being observed with PB. Significant differences in synergism among synergists were not observed. For S. litura, the highest SR(=8.8) was observed with PB. At all time periods, the penetration of 14C-deltamethrin was relatively faster to S. litura than to H. assulta. Time (hrs) required for 20% ( t 20) of the applied doses to be excreted from treated S. litura was 1.5-fold faster than that of H. assulta. Higher synergism and longer retention in larval body of S. litura by the addition of PB suggest that the mixed function oxidase be a major factor in detoxification of deltamethrin. The combined use of PB with deltamethrin, and possibly other pyrethroids, might indicate a potential for controlling field populations resistant to deltamethrin and other pyrethroids.

Monooxygenases play only a minor role in resistance to synthetic pyrethroids in the cattle tick, Boophilus microplus.

We investigated the role of monooxygenases in resistance to synthetic pyrethroids (SPs) in the cattle tick, Boophilus microplus. We found that monooxygenases play only a minor role in resistance to SPs in both resistant and susceptible strains of B. microplus. We blocked the monooxygenases with piperonyl butoxide (PBO) and simultaneously applied the SPs, flumethrin and cypermethrin to larval B. microplus. PBO increased the effect of flumethrin (synergism ratios 2.7-8.9) more than it increased the effect of cypermethrin (synergism ratios 1.9-3.1). Of the four strains tested, Parkhurst, which is resistant to SPs, was the least affected by the addition of PBO (synergism ratios after cypermethrin was applied 1.9; after flumethrin 2.7) whereas N.R.F.S., the strain susceptible to SPs, was the most affected by synergism between PBO and SPs (synergism ratio after cypermethrin was applied 3.1; after flumethrin 8.9). We hypothesize that B. microplus lacks monooxygenases capable of conferring resistance to SPs because it and its recent ancestors were blood-feeders rather than herbivores.

Aspects of extraction, spiking and distribution in the determination of incurred residues of chloramphenicol in animal tissues

Studies of distribution, extraction procedures and spiking protocols in the determination of incurred chloramphenicol residues in animal tissues have been carried out. An extraction procedure involving glucuronidase enzyme digestion was found to extract 10 times more incurred chloramphenicol from pig kidney than direct extraction without digestion. However, neither protease digestion nor ultrasonic probe treatment resulted in improved chloramphenicol extraction. Chloramphenicol was found to be inhomogeneously distributed within kidney from a treated pig. Highest concentrations were detected in the renal medulla. Muscle tissues from the same animal were found to contain a lower concentration of chloramphenicol residues, but no chloramphenicol residues were detectable in the liver. Chloramphenicol recovery from spiked pig liver was found to be lower than that from kidney, but was improved by the addition of piperonyl butoxide before extraction. This additive had no effect on recovery from spiked pig or cattle kidney. The implications of these results for regulatory surveillance of animal tissue for chloramphenicol residues are discussed.

Effect of the Monooxygenase Inhibitor Piperonyl Butoxide on the Herbicidal Activity and Metabolism of Isoproturon in Herbicide Resistant and Susceptible Biotypes ofPhalaris minorand Wheat

Experiments were carried out under controlled environmental conditions to compare the dose response of isoproturon to resistant (R) and susceptible (S) biotypes ofPhalaris minorand wheat and the effect of the cytochrome P-450 inhibitor, piperonyl butoxide (PBO), on the efficacy of isoproturon. Qualitative and quantitative assessments were undertaken on the influence of PBO on metabolism of [14C]isoproturon applied to the base of cut leaves. Resistance to isoproturon in the R biotype was found to be circa 12-fold of that occurring in the S biotype. Addition of PBO lowered the GR50(growth reduction by 50%) values of the R biotype by 14 times compared to isoproturon alone; in the S biotype ofP. minorand wheat comparable reductions were only 2 times. Over 48 h the rate of degradation of [14C]isoproturon was more rapid in the R biotype ofP. minorand wheat; the major metabolites were hydroxy isoproturon, monodesmethyl isoproturon, carboxylic acid metabolite, didesmethyl isoproturon, conjugates, and two unidentified metabolites. The hydroxy metabolite was present in a greater proportion in the R than the S biotype. In all the test plants the addition of PBO significantly inhibited demethylation and hydroxylation as 80–94% of the applied [14C]isoproturon was found to be unchanged after 24 h; only 45 to 56% recovery was obtained without PBO. Hydroxylation and demethylation seem to be the major breakdown pathways of isoproturon inP. minorbiotypes and wheat. The rapid degradation of [14C]isoproturon in the R biotype ofP. minorin the absence of PBO indicates that resistance is governed by increased activity of cytochrome P-450 monooxygenase enzymes. This study illustrates the important role which monooxygenases play in conferring differential sensitivity ofP. minorand wheat to the action of isoproturon.

Response of a Chlorsulfuron-Resistant Biotype ofKochia scopariato ALS Inhibiting Herbicides and Piperonyl Butoxide

Greenhouse and laboratory studies were conducted to determine kochia resistance to a spectrum of acetolactate synthase (E.C.4.13.18) (ALS)-inhibiting herbicides. The chlorsulfuron-resistant biotype plants were resistant to six herbicides: triflusulfuron, thifensulfuron, halosulfuron, imazamethabenz, chlorsulfuron, and nicosulfuron. But, the resistant biotypes showed sensitivity similar to the susceptible biotypes to three herbicides: metsulfuron, imazethapyr, and imazaquin. The resistant biotypes were slightly less sensitive to primisulfuron, chlorimuron, and flumetsulam than the sensitive biotypes. The I50values for 50% inhibition of the ALS enzyme indicated that the resistant biotype was 22, 18, and 16 times more resistant to primisulfuron, chlorsulfuron, and thifensulfuron than the susceptible biotype. In contrast, the I50ratios (resistant/susceptible) were 3, 2, and 1 for flumetsulam, nicosulfuron, and imazethapyr, respectively. The altered ALS enzyme system of the resistant biotype showed a differential response for the ALS-inhibiting herbicides. Addition of a mixed function oxidase inhibitor, piperonyl butoxide (PBO) at 2 kg ha−1, to primisulfuron and thifensulfuron increased visual injury and reduced plant height of the chlorsulfuron-sensitive kochia biotype plants. The addition of PBO to primisulfuron enhanced visual injury of the resistant biotype at low rates of primisulfuron.

Ascorbic Acid Inhibition of Cytochrome P450-Catalyzed Uroporphyrin Accumulation

Previous studies on the mechanism of the uroporphyria caused by polyhalogenated aromatic hydrocarbons have indicated a key role of cytochrome P450 of the 1A subfamily in catalyzing uroporphyrinogen (UROgen) oxidation. Here we report that ascorbic acid (ASC) inhibits UROgen oxidation in primary cultures of chick embryo hepatocytes and hepatic microsomes from chickens and mice. In hepatocyte cultures, 0.15 mM ASC totally prevented the accumulation of uroporphyrin (URO) induced by treatment of cells with the combination of 3,4,3′,4′-tetrachlorobiphenyl (TCB) and 2-propyl-2-isopropylacetamide (PIA), but had no effect on the induction of protoporphyrin accumulation by PIA and desferrioxamine. However, addition of 5-aminolevulinic acid (ALA) to cultures treated with PIA plus TCB decreased the ability of ASC to prevent URO accumulation, suggesting that the effectiveness of ASC was dependent on the intracellular concentration of ALA or its metabolites. Similarly, when chick hepatocyte cultures were treated with TCB plus exogenous ALA to produce URO accumulation, the effectiveness of ASC was also less than when ALA was produced endogenously. Under this condition, addition of piperonyl butoxide, a P450 inhibitor, increased ASC inhibition of URO accumulation. ASC competitively inhibited the oxidation of UROgen by hepatic microsomes from chicks or mice treated with 3-methylcholanthrene (MC) with K i for ASC being about 0.1 mM. ASC prevented formation of a 500-nm absorbing compound, probably tetrahydrouroporphyrin, the first intermediate in UROgen oxidation. These results are consistent with ASC preventing URO accumulation in hepatocytes by competitive inhibition of the first step of UROgen oxidation and suggest a new physiological role of ASC, that of maintaining UROgen in the reduced state.

Reduction of the Toxicity of Fenitrothion to Prawns by Piperonyl Butoxide.

The effectiveness of piperonyl butoxide (PB) in reducing the mortality of striped prawn and kuruma prawn during exposure to fenitrothion (FS) was examined. The 24-h LC50 values of PB for striped and kuruma prawns were 3.5 and 1.6 ppm at 25°C, respectively. Therefore, PB-treatment for both prawns was conducted at 0.25 ppm, corresponding to one-tenth of the mean of both 24-h LC50 values. The PB-pretreatment before FS-exposure and also the addition of PB to FS-water were effective in decreasing the FS-toxicity to both prawns. The most effective reduction of the toxicity to the prawns was obtained by continuous PB-treatment before and during FS-exposure, resulting in extensions of 50% survival time by 4-6 times in striped prawn and 10-16 times in kuruma prawn, compared with the respective control groups non-treated with PB.

Inheritance of metabolic resistance to the synthetic pyrethroids in Australian Helicoverpa armigera(Lepidoptera: Noctuidae)

AbstractTwo strains of Helicoverpa armigera (Hübner), resistant to synthetic pyrethroids, were isolated from field populations collected in the irrigated cotton growing areas of northern New South Wales: an isofemale strain, Mfo, and a composite field strain, Field. A series of crosses were undertaken between the Mfo and susceptible strains to determine the genetic basis of the resistance. Dose-responses were obtained by bioassay using topical application of fenvalerate in acetone. Considerable variation in tolerance was observed in both resistant and susceptible strains. In the Mfo strain, the major shift in resistance phenotype (33-fold resistance) was due to a single major gene with incomplete dominance. The resistance phenotype was not diluted by 23 generations of backcrossing. The major resistance phenotype could be eliminated almost completely by the addition of piperonyl butoxide which affects oxidative breakdown of the pyrethroids by mixed function oxidase (mfo) enzymes. Similar results were observed in the Field strain. Monitoring for resistance in field populations will be imprecise because a true discriminating dose does not exist for susceptible and heterozygous resistant individuals.

The effects of direct and microsomal activated aflatoxin B 1 on chicken peritoneal macrophages in vitro

Sephadex-elicited peritoneal exudate cells were cultured on glass coverslips in order to determine the effects of aflatoxin B 1 (AFB 1) on chicken macrophages. Adherent macrophage monolayers were exposed for 1 h to 5, 10, and 20 μg ml −1 of AFB 1, directly or to 0.01, 0.1, 0.5, 1, and 5 μg ml −1 of AFB 1 in the presence of a chicken microsomal mixed function oxidase system (MFO). After exposure, the macrophage cultures were washed and allowed to recover for 2 h in fresh culture medium. Parameters measured at 2 h post recovery period were the substrate adherence potential, morphological alterations, phagocytic ability, and number of sheep red blood cells (SRBC) internalized per phagocytic macrophage. Direct in vitro exposure to AFB 1 resulted in a dose-dependent decrease in macrophage adherence potential, and an increase in cell damage as determined by nuclear disintegration and cytoplasmic blebbing, but no detrimental effects were observed on percent phagocytic cells or the number of internalized SRBC. However, significant reductions in adherence potential, increased morphological alterations, and reduced phagocytosis and internalization of SRBC were observed when MFOs were added to cultures treated with much lower doses of AFB 1. Addition of piperonyl butoxide (a P-450 inhibitor) abrogated AFB 1-MFO induced alterations. This study suggests that microsomal activated AFB 1 causes significant alterations in chicken macrophage functions.

Direct and microsomal activated aflatoxin B 1 exposure and its effects on Turkey peritoneal macrophage functions in vitro

Sephadex-elicited turkey peritoneal exudate cells were used to establish adherent macrophage monolayers on glass coverslips in order to determine the effects of aflatoxin B 1 (AFB 1) on macrophages. Adherent macrophage monolayers were exposed to increasing doses of AFB 1 (5, 10, 20, and 40 μg), either directly, or to 0.01, 0.1, 0.5, 1, and 5 μg of AFB 1 in the presence of a chicken microsomal mixed function oxidase system (MFO). Cultures were incubated with the appropriate treatments for 1 hr, then washed and allowed to recover in fresh growth medium for 2 hr. Direct exposure of macrophages to AFB 1 had no detrimental effect on macrophage adherence, percentage damaged, percentage phagocytic, and the number of antibody-coated or uncoated sheep red blood cells internalized per phagocytic macrophage when compared with the sham or solvent treated cultures. However, the addition of MFOs to the cultures treated with much lower doses of AFB 1 resulted in significantly higher morphological alterations along with a reduction in cell adherence and phagocytic potential. Addition of piperonyl butoxide (a P450 inhibitor) abrogated AFB 1-MFO induced alterations. Data collected in this study suggest that turkey macrophages are resistant to the direct exposure of AFB 1 and that AFB 1 induced alterations in macrophage effector functions are due to metabolic activation of AFB 1 by MFOs.

Feeding Inhibition and Mortality Effects of Neem-Seed Extract on the Colorado Potato Beetle (Coleoptera: Chrysomelidae)

In laboratory experiments, concentrations of 0.4, 0.8, and 1.2% (wt/vol) neem-seed extract inhibited feeding of adult and larva of Colorado potato beetle, Leptinotarsa decemlineata (Say), on treated potato foliage, Solanum tuberosum L. Adult mortality did not exceed 25% in any neem treatment; however, 73% of larvae were dead 72 h after feeding on foliage treated with 1.2% neem extract. Toxicity of neem extract to larvae was enhanced, and feeding of larvae and adults was inhibited to a greater extent by addition of the synergist piperonyl butoxide (PBO) at a ratio of 10:1 (PBO/azadirachtin). In field experiments, spray applications of neem extract significantly reduced numbers of L. decemlineata larvae and adults in treated plots on all sample dates. The effectiveness of neem extract against L. decemlineata was signifcantly improved on two dates by addition of PBO. The 1.2% neem + PBO treatment resulted in low tuber yield, suggesting possible phytotoxic effects.

Mechanisms of resistance to pyrethroids and 1,1,1-trichloro-2,2-bis( p-chlorophenyl)ethane in the house fly, Musca domestica L

The quantitative responses of a femur motor nerve preparation of pyrethroid-resistant 228e2b and susceptible SRS strains of house flies were evaluated electrophysiologically, following application of pyrethroids and 1,1,1-trichloro-2,2-bis( p-chlorophenyl)ethane (DDT) to the exposed thoracic ganglia of the two reference strains. The 228e2b strain was resistant to DDT and to all the test pyrethroids with Type I and Type II actions. The nervous system of the 228e2b strain was far less sensitive to both classes of insecticides than that of the susceptible strain. Pretreatment with oxidase inhibitor piperonyl butoxide (PB), esterase inhibitor IBP, or DDT dehydrochlorinase inhibitor, 2-(dimethylamino)ethyl chloride did not alter the latency of appearance of symptoms and firing frequency in motor nerves. Cross-resistance was detected in the resistant strain in spite of addition of PB. These results suggest that enhanced metabolism might not be an important factor in the strain. Rates of penetration of [ 14C]permethrin were very similar in the two reference strains. Based upon our toxicological and electrophysiological data, nerve insensitivity plays a great role in resistance to pyrethroids in the 228e2b strain of house flies, although several resistance factors may be involved.

Effect of Pyrethroids on Knockdown and Lack of Coordination Responses of Susceptible and Resistant Diamondback Moth (Lepidoptera: Plutellidae)

Among DDT and the 10 pyrethroids tested, permethrin, cypermethrin, deltamethrin, and fenvalerate were most toxic against a field strain of Plutella xylostella (L.) that had high levels of resistance to all insecticides tested. Knockdown effect of these compounds against larvae and adults of susceptible and resistant strains was evaluated by a residual-film method. Symptoms of poisoning are described. When larvae or adults could no longer stand and had to lie on their sides, they were considered knocked down. Pyrethroids with primary alcohol esters produced more acute symptoms than those with secondary alcohol esters. Responses of resistant larvae and adults were less pronounced than those of susceptible ones. In the resistant strain, addition of synergist piperonyl butoxide (PB) to the pyrethroids produced symptoms displayed by the susceptible strain. Tetramethrin, which was not highly toxic, was the most potent knockdown agent against susceptible larvae. Knockdown action of all pyrethroids appeared much more slowly in resistant larvae; fluvalin ate and flucythrinate were least effective as knockdown as well as killing agents. Addition of synergists PB, S,S,S-tributyl phosphorotrithioate, and chlordimeform generally enhanced knockdown action of most pyrethroids in resistant larvae, but had only limited effect in susceptible larvae. Maximal knockdown of adults by fenvalerate was reached 60–90 min after exposure; PB synergized this action of fenvalerate and reduced recovery of the moths within 24 h.

DDT‐resistant mosquito strains with cross‐resistance to pyrethroids

AbstractVarious DDT‐resistant strains of mosquito, comprising 8 strains of Aedes aegypti from the Neotropics (tropical and South America) and one each of Anopheles gambiae and An. quadrimaculatus were tested for resistance to pyrethroids. Susceptibility was measured by LT50 values, after exposure to impregnated papers in the cylinders used in the WHO standardised test for adult mosquitoes. DDT‐resistance levels (by comparison with susceptible strains) ranged from × 2 to × 73, with simultaneous low resistance to permethrin (× 1.4 to × 3.4) except in one strain from Guyana which reached × 30. Further comparisons were made with this Guyana strain and one from Salvador with similar DDT‐resistance (about × 70) but low permethrin‐resistance. Tests with methoxychlor and I,I‐di‐(4‐chlorophenyl)‐2‐nitropropane and with the synergist I,I‐di‐(4‐chlorophenyl)‐2,2,2‐trifluoroethanol suggested that a considerable part of the DDT‐resistance of both strains was due to a dehydrochlorination mechanism. Tests with the synergist piperonyl butoxide (PB) suggested that microsomal oxidase systems were also involved, especially in the Guyana strain. The cross‐resistance in both strains extended to 3 other pyrethroids. Addition of the synergist PB had little effect on the Salvador strain, but substantially reduced permethrin‐resistance in the Guyana strain. It is concluded that an unknown mechanism associated with DDT‐resistance confers a low level cross‐tolerance to pyrethroids; this can be substantially augmented by the development of a microsomal oxidase mechanism, as in the Guyana strain.

Effect of benzo(a) pyrene and piperonyl butoxide on formation of respiratory system, phospholipids, and carotenoids of Staphylococcus aureus.

Staphylococcus aureus formed an electron transport system when exponentially growing cells were aerated. Formation of the electron transport system occurred concomitantly with increases in the phospholipids and the carotenoids. The addition of piperonyl butoxide or benzo(a)pyrene at the onset of aeration (i) slowed the formation of the electron transport system, (ii) both inhibited cytochrome oxidase o synthesis and decreased its stability, (iii) simultaneously depressed the increase in total phospholipid (especially cardiolipin), and (iv) depressed the synthesis of the carotenoid rubixanthin. Benzo(a)pyrene was the more inhibitory of the two, both on the rate of synthesis of the electron transport system and on rubixanthin formation. Evidence obtained with the inhibitors suggested that inhibition of the lipid synthesis was related to the formation of the electron transport system.

Utilization of cell culture techniques in carbaryl metabolism studies

Radioactive carbaryl (1-naphthyl N-methylcarbamate), introduced into a culture of human embryonic lung cells (L-132 strain), was completely metabolized within 3 days to water-soluble conjugates or organoextractables in the medium. No radioactivity was found in the washed cells. Studies to elucidate the metabolic pathways of detoxification suggested that carbaryl was hydroxylated in the C4 position of the ring and that approximately 40% of the labeled compound was hydrolyzed to form naphthalene-1, 4-diol. The remainder was found as theN-glucuronides of 4-hydroxycarbaryl and 5,6-dihydroxy-5,6-dihydrocarbaryl. The addition of piperonyl butoxide to the cell culture medium had no effect upon the detoxification of carbaryl.

Reactions of larvae of Plodia interpunctella (HB) (LEP., pyralidae) to insecticidal droplets.

In tests of the reactions of freshly hatched larvae of Plodia interpunctella (Hb.) to droplets of liquids containing an insecticnde, 16 droplets of the test material were disposed in a ting 23 mm. in diameter on a glass surface. The mean diameter of dtoplets of the different oils used as solvents varied from about 330 to 615 μ. Minute glass beads about 680 μ in diameter were used as controls. The larvae were tested individually by placing them at the ecntre of the ring and noting whether ot not they succeeded in escaping from it without making contact with a droplet, and their time to do so, termed the avoiding-time.Six petroleum hydrocarbon oils, and pyerthrin at different concentrations in one of them (Shell Risella Oil 17) and pyrethrin synergists, piperonyl butoxide and Bucarpolate (2-(2-n-butoxyethoxy)ethyl 3,4-methylenedioxybenzoate), were tested. Droplets containing 20 per cent. pyrethrins proved the most repellent, over 98 per cent. of the larvae avoiding contact with them, whereas only 47.5 per cent. avoided the glass beads. The degree of avoidance elicited by the oils was inversely related to the values of their physical characteristics, such as initial boiling point and mean molecular weight. Increasing concentrations of pyrethrins increased both the degree of avoidance and the avoidingtime, and the addition of piperonyl butoxide or Bucarpolate enhanced both these reactions.