Showing papers in "Pesticide Science in 1980"
TL;DR: It is concluded that birds are deficient in A-esterase activity towards pirimiphos-methyloxon and paraoxon, and the importance of this deficiency in determining the relatively high susceptibility of birds to these and other organophosphorus insecticides is discussed.
Abstract: Pirimiphos-methyloxon (2-diethylamino-6-methylpyrimidin-4-yl dimethyl phosphate) the phosphate analogue of pirimiphos-methyl, and paraoxon (diethyl 4-nitrophenyl phosphate) the phosphate analogue of parathion were used as substrates to determine the esterase activity in plasma. Aryl groups released were measured by high-performance liquid chromatography or with a recording spectrophotometer. In a survey of 14 species of birds representing six different avian orders, the plasma esterase activities (expressed as nmol min−1 ml−1 of plasma) were always low, ranging from 0-71 for pirimiphos-methyloxon and from 0-0.63 for paraoxon. By contrast, mammalian activities were very much higher than these, and in no case was a sample of mammalian plasma less than 13 times more active than any sample of avian plasma using the same assay procedure. It is concluded that birds are deficient in A-esterase activity towards pirimiphos-methyloxon and paraoxon. The importance of this deficiency in determining the relatively high susceptibility of birds to these and other organophosphorus insecticides is discussed.
132 citations
TL;DR: This review of studies on 20 pyrethroids with nine different acid moieties and ten different alcohol moieties reveals a diversity of functional groups undergoing metabolism in mammals, insects, other organisms, and microsomal esterase and oxidase systems.
Abstract: This review of studies on 20 pyrethroids with nine different acid moieties and ten different alcohol moieties reveals a diversity of functional groups undergoing metabolism in mammals, insects, other organisms, and microsomal esterase and oxidase systems Seventy-nine metabolites are identified from the cis-isomer of permethrin and transpermethrin but fewer from other pyrethroids examined in less detail The sites and rates of metabolic attack on each pyrethroid depend on the organism or system Metabolism of pyrethoids by esterase and oxidase action usually limits their toxicity to mammals more than to insects, thereby conferring useful selective toxicity properties
94 citations
TL;DR: In this article, the uptake of pesticides by earthworms from aqueous solutions was examined and shown to be a reversible physical process, where adsorption coefficients were related to octanol-water distribution coefficients, as are soil-water distributions.
Abstract: The uptake of pesticides by earthworms from aqueous solutions was examined and shown to be a reversible physical process. Measurements of distributions of pesticides between aqueous solutions and worm solids showed that adsorption coefficients were related to octanol-water distribution coefficients, as are soil-water distributions. From these relationships it was calculated that concentration factors of stable chemicals in earthworms from soil should be similar, except for polar substances which penetrate poorly, and be determined mainly by the soil organic matter content. Examination of uptake from soils indicated that the calculated concentration factors are unlikely to be achieved because of slow diffusion of chemicals in soils and because of metabolism in the soil or the worm.
91 citations
TL;DR: In this paper, the breakdown of oxamyl was studied in three downland chalk soils, a peat loam, a sandy loam and the same sand loam modified by adding peat.
Abstract: The breakdown of oxamyl was studied in three downland chalk soils, a peat loam, a sandy loam, and the same sandy loam modified by adding peat. The kinetics of aldicarb degradation via its sulphoxide and aldoxycarb (aldicarb sulphone) were also studied in these two sandy loam soils. All the reactions followed first-order kinetics, the reaction being faster in the original than in the modified sandy loam. Rates of reaction were slower at low moisture contents, and decreased markedly when the temperature was reduced from 10 to 5°C though less so than from 15 to 10°C.
74 citations
TL;DR: The sequences of compounds, leading from the natural pyrethrins to the present established pyrethroids, are described so as to provide a background for considering the more recent advances discussed in succeeding papers.
Abstract: The sequences of compounds, leading from the natural pyrethrins to the present established pyrethroids, are described so as to provide a background for considering the more recent advances discussed in succeeding papers.
58 citations
TL;DR: Careful monitoring of the changes in activity between parents and offspring of the most resistant variant of Anholocyclic Myzus persicae showed that complete loss of resistance can occur either in a single step or over several generations, and that below a threshold value, reversion to higher levels is very rare.
Abstract: Anholocyclic Myzus persicae (Sulz.) from the glasshouse and field can be classified into six variants, each with a characteristic carboxylesterase activity and consequent resistance to carbamate and organophosphorus insecticides. Overlapping activity distributions prevent unequivocal identification of an individual from measurements of its enzyme activity, but this may be done by cloning and measuring the frequency distribution of the enzyme activity in its progeny. Although each of the four lowest esterase variants has a frequency distribution with a single peak, only the susceptible (USLL) is best described by a single Normal distribution. Those of the other three clones (MSIG, French R and T1V) correspond better with two Normally-distributed components. However, these are not well separated and the lower component accounts for only 10-25% of the individuals. The very resistant clones from glasshouses have higher mean activities but with very broad distributions covering the whole range observed in this aphid. These broad distributions have peaks corresponding to those of the less resistant variants and arise from the appearance at each generation of a small proportion of individuals with much less active enzyme than their parents. Careful monitoring of the changes in activity between parents and offspring of the most resistant variant (clone G6) showed that complete loss of resistance can occur either in a single step or over several generations, and that below a threshold value, reversion to higher levels is very rare. Such reversion could only be detected by selection, with insecticide, of large clonal populations from an individual that had lost activity. High esterase activity was not stabilised by breeding for 16 generations only from individuals with high esterase activity, and is probably maintained in glasshouses by continuous exposure to insecticides. Spontaneous loss of esterase activity and resistance was observed only in glasshouse populations.
58 citations
TL;DR: Aldicarb and its oxidation product aldoxycarb (aldicarb sulphone) were applied separately to columns of fallow, sandy loam soils under field conditions as mentioned in this paper.
Abstract: Aldicarb and its oxidation product aldoxycarb (aldicarb sulphone) were applied separately to columns of fallow, sandy loam soils under field conditions. The breakdown and movement of these compounds were monitored, as was the behaviour of aldicarb sulphoxide and aldoxycarb formed by oxidation of the applied aldicarb. The behaviour of these compounds was simulated by a computer model using laboratory data for adsorption and rates of degradation in soil. The model simulated the observed behaviour reasonably well, although redistribution of chemicals was often more rapid than predicted. Production of aldoxycarb from the sulphoxide was less in the field than was expected from the laboratory incubations. Accumulation of chemicals near the soil surface in dry periods was overestimated, indicating that the processes occurring under these conditions are not well described by the model. About 4 months after application, only aldoxycarb, in small amounts, remained in the soils.
41 citations
TL;DR: Novel halogenated chrysanthemic acid analogues have been prepared and the interesting properties of their esters are described, including the most active insecticides yet reported.
Abstract: Novel halogenated chrysanthemic acid analogues have been prepared and the interesting properties of their esters are described. Among this group are the most active insecticides yet reported.
40 citations
TL;DR: In this article, the movement and breakdown of the insecticide and nematicide oxamyl were monitored in fallow sandy loam soils under field conditions using measurements of rainfall and evaporation from a water surface, the water flow in soil was simulated by a computer model and the results were compared with the measured soil-moisture profiles.
Abstract: The movement and breakdown of the insecticide and nematicide oxamyl was monitored in fallow sandy loam soils under field conditions. Using measurements of rainfall and evaporation from a water surface, the water flow in soil was simulated by a computer model, and the results were compared with the measured soil-moisture profiles. The model was extended to simulate the behaviour of oxamyl, using laboratory data for adsorption and rates of degradation in soil. The model generally underestimated oxamyl movement in the first month, whereas it tended to overestimate later movement. The rate of breakdown of oxamyl, as affected by soil type, temperature and soil-moisture content, was fairly well described. After about 2 months only small amounts of oxamyl remained. Accumulation of oxamyl near the soil surface in dry periods was overestimated, indicating deficiencies in the modelling procedure under these conditions.
39 citations
TL;DR: The degradation of bis(tri[1-14C]butyltin) oxide in two soils (1 mg tin kg−1) has been studied under laboratory conditions.
Abstract: The degradation of bis(tri[1-14C]butyltin) oxide in two soils (1 mg tin kg−1) has been studied under laboratory conditions. Half of the applied compound disappeared from unsterilised silt loam and sandy loam in approximately 15 and 20 weeks, respectively; it disappeared also from the sterilised soils but to a lesser extent. The formation of small amounts of dibutyltin derivatives was established by thin-layer chromatography both in the unsterilised and sterile soils. The amount of unextractable radioactivity increased with time in the unsterilised and sterile soils. In the unsterilised soils 14C was released as [14C]carbon dioxide in amounts equivalent to 20% of the applied radioactivity for silt loam and 10.7% for sandy loam over a period of 42 weeks. Almost no [14C]carbon dioxide was released from the sterile soils, confirming microbial participation in the degradation of the compound in the unsterilised soils.
37 citations
TL;DR: Both treatments effectively prevented the production of progeny and the order of persistence was pirimiphos-methyl> (1R)-phenothrin>carbaryl or fenitrothion.
Abstract: Duplicate field trials were carried out on bulk wheat in commercial silos in Queensland and New South Wales. Laboratory bioassays on samples of treated grain at intervals over 9 months, using malathion-resistant strains of insects, established that treatments were generally effective. Fenitrothion (12 mg kg−1)+ (1R)-phenothrin (2 mg kg−1) was more effective than pirimiphos-methyl (6 mg kg−1) + carbaryl (10 mg kg−1) against Sitophilus oryzae (L.) and Ephestia cautella (Walker); the order of effectiveness was reversed for S. granarius (L.). Against Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), T. confusum Jackquelin du Val and Oryzaephilus surinamensis (L.), both treatments effectively prevented the production of progeny. The order of persistence was pirimiphos-methyl> (1R)-phenothrin>carbaryl or fenitrothion. During processing from wheat to white bread, residues were reduced by 98% for carbaryl, >44% for (1R)-phenothrin, 98% for fenitrothion and 85% for pirimiphosmethyl.
TL;DR: Limited synergism of the pyrethroids by S,S,S-tributyl phosphorotrithioate and piperonyl butoxide and of DDT by chlorfenethol and PB suggested that some non-metabolic mechanism, such as kdr, may be an important component of resistance to pyre Throids as well as to DDT in this mosquito.
Abstract: Strains of Culex quinquefasciatus Say, selected with biopermethrin [(1R)-trans-permethrin] or with (1R)-cis-permethrin, were examined in the larval stage for crossresistance to 30 pyrethroids, DDT, dieldrin, temephos, propoxur, and two organotin compounds. The (1R)-trans-Permethrin-R strain [resistance factor (RF) = 4100-fold] and the (1R)-cis-Permethrin-R strain (RF= 450-fold) of C. quinquefasciutus were cross-resistant to all pyrethroids tested [RF= 12-fold for an allethrin isomer to about 6000-fold for (RS,RS)-fenvalerate] as well as to DDT (RF= about 2000-fold). However, they were not significantly Cross-resistant to dieldrin, temephos, propoxur, and the two organotin compounds. Changes in the alcohol moiety, structural isomerism, and susceptibility of the cyclopropane C-3 side chain to oxidative attack are important factors in determining the level of cross-resistance to various pyrethroids. Limited synergism of the pyrethroids by S,S,S-tributyl phosphorotrithioate and piperonyl butoxide (PB), and of DDT by chlorfenethol and PB, suggested that some non-metabolic mechanism, such as kdr, may be an important component of resistance to pyrethroids as well as to DDT in this mosquito.
TL;DR: The biological efficacy of methacrifos was greater and the rate of degradation lower in aerated than in non-aerated storage, and residue levels were below proposed international residue levels to be considered by the Codex Alimentarius Commission.
Abstract: Field trials with various pesticide combinations were carried out on bulk wheat in commercial silos in Queensland, South Australia and Western Australia. Laboratory bioassays on samples of treated grain at intervals over 8 months using malathion-susceptible and malathion-resistant strains established the following orders of efficacy: against Sitophilus oryzae (L.), chlorpyrifos-methyl 10 mg kg−1 + bioresmethrin 1 mg kg−1 = methacrifos 15 mg kg−1 in aerated storage > pirimiphos-methyl 4 or 6 mg kg−1 + bioresmethrin 1 mg kg−1 = bioresmethrin 4 mg kg−1 + piperonyl butoxide 16 mg kg−1; against Rhyzopertha dominica (F.), bioresmethrin 4 mg kg−1 + piperonyl butoxide 16 mg kg−1 > methacrifos 15 mg kg−1 > chlorpyrifos-methyl 10 mg kg−1 + bioresmethrin 1 mg kg−1 = pirimiphos-methyl 4 or 6 mg kg−1 + bioresmethrin 1 mg kg−1. All treatments completely prevented production of progeny in Sitophilus granarius (L.), Tribolium castaneum (Herbst), T. confusum Jackquelin du Val and Oryzaephilus surinamensis (L.). The biological efficacy of methacrifos was greater and the rate of degradation lower in aerated than in non-aerated storage. Residue levels of all compounds were determined chemically and were below proposed international residue levels to be considered by the Codex Alimentarius Commission.
TL;DR: The half-lives of (Z)- and (£>l, 3-dichloropropenes at 20°C in soils were found to vary from 3 to 25 days as discussed by the authors.
Abstract: The rates of dissipation in soil and chloride-ion release, of the main components of dichloropropane-dichloropropene mixtures used as nematicides, were studied in sealed glass containers at different temperatures and moisture conditions. Half-lives of (Z)- and (£>l,3-dichloropropenes at 20°C in soils were found to vary from 3 to 25 days; those of 1,2-dichlorop ropane and 2,3-dichloropropene were about four times and twice as long, respectively. The dissipation rates changed by a factor of about 2 per 10°C change in temperature. Judging from the release rates of waterextractable inorganic chloride in the soil (0-4% per week), the total degradation of all components applied at normal field rates was extremely slow. This indicated the formation of residues containing covalently bound chlorine. Only in 'enrichment cultures' was complete degradation indicated.
TL;DR: The relationship between stereochemistry and the biologically active enantiomers of esters formed from the major secondary alcohols is discussed in this article, with essential descriptions of synthetic pathways, optical resolution and determination of absolute configuration.
Abstract: Four important classes of synthetic pyrethroids containing certain secondary alcohol moieties, namely the α-cyano-3-phenoxybenzyl esters, the analogous α-ethynyl esters, 1-(3-phenoxyphenyl)prop-2-ynyl esters and 2-methyl-4-oxo-3-(prop-2-ynyl)-cyclopent-2-enyl esters and their most active isomers, are introduced with essential descriptions of synthetic pathways, optical resolution and determination of absolute configuration. The relationship between stereochemistry and the biologically active enantiomers of esters formed from the major secondary alcohols is discussed.
TL;DR: Methanol was more efficient than solvent systems based on acetonitrile or chloroform for the extraction of a number of weathered herbicide residues from soil, and the presence of water in the soil improved recovery as discussed by the authors.
Abstract: Methanol was more efficient than solvent systems based on acetonitrile or chloroform for the extraction of a number of weathered herbicide residues from soil. The presence of water in the soil improved recovery. Methanolic extracts, on examination by gas-liquid chromatography, also gave lower background levels than the extracts with other solvents.
TL;DR: A new series of substituted 2-anilino-3-methylbutyrates has been prepared and bioassay data for these compounds on Heliothis virescens, Musca domestica, Aphis fabae and Tetranychus urticae are presented and discussed.
Abstract: A new series of substituted 2-anilino-3-methylbutyrates has been prepared; bioassay data for these compounds on Heliothis virescens, Musca domestica, Aphis fabae and Tetranychus urticae are presented and discussed Some unexpected relationships were observed between the nature of the substituents and the biological activity Increases in foliar stability were noted with certain substitution patterns Both α-cyano-3-phenoxybenzyl 3-methyl-2-(α, α, α,2-tetrafluoro-p-toluidino)butyrate and the corresponding 2-(2-chloro-α, α, α-trifluoro-p-toluidino)-3-methylbutyrate showed good stability in air and light, and exhibited biological activities of a similar nature and potency to those of previously known synthetic pyrethroids Esters of the (R)-2- anilino-3-methylbutyric acids are far more active than those prepared from the (S)-enantiomers The (R)-configuration at C-2 in these acids is sterically equivalent to the active absolute configuration at the chiral carbon α to the carboxylate group in both the permethrin and the fenvalerate types of pyrethroids A new class of insecticidal 2-(isoindolin-2-yl)alkanoates is also reported In this series the most biologically active analogue was α-cyano-3-phenoxybenzyl 3-methyl-2-(4,5,6,7-tetrafluoroisoindolin-2-yl)butyrate These esters were considerably less stable than the anilino analogues on exposure to air and light
TL;DR: A short account of the occurrence, separation, and properties of the insecticidal ester pyrethrins from Chrysanthemum cinerariaefolium is given in this article.
Abstract: A short account is given of the occurrence, separation, and properties of the insecticidal ester pyrethrins from Chrysanthemum cinerariaefolium. Methods for the synthesis of the two component acids, chrysanthemic and 'chrysanthemumdicarboxylic acid' [3-(2-carboxyprop-1-enyl)-2,2-dimethylcyclopropanecarboxylic acid], and the alcohols (rethrolones) are surveyed, and brief consideration is given to the limited knowledge of the biosynthesis of this group of compounds.
TL;DR: In this paper, the effect of the absolute configuration at the chiral centres of the dibromo adducts of the dichlorovinyl group of cyper methrin has been investigated.
Abstract: Bromination of the dichlorovinyl group of cypermethrin yielded a new compound which is a highly potent insecticide. This dibromo adduct has four asymmetric centres and therefore can exist as a mixture of 16 stereoisomers. To establish the influence of the absolute configuration at the chiral centres on the biological activities of these isomers, each of the isomers was isolated; their insecticidal activities against larvae of Heliothis virescens, and adult Calliphora erythrocephala and Blattella germanica were then determined and compared with those of (S)-α-cyano-3-phenoxybenzyl (1R)-cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate (deltamethrin NRDC 161), of fenvalerate, and of the eight stereoisomers of cyper methrin.
TL;DR: Comparisons with standard susceptible insects showed that a strain of Tribolium castaneum, with a specific resistance to malathion and its carboxylic ester analogues, had no cross-resistance to topical applications of natural pyrethrins and generally larger resistance factors were recorded with formulations synergised by piperonyl butoxide.
Abstract: Comparisons with standard susceptible insects showed that a strain of Tribolium castaneum, with a specific resistance to malathion and its carboxylic ester analogues, had no cross-resistance to topical applications of natural pyrethrins. Another strain of T. castaneum, showing resistance to many organophosphorus (OP) insecticides, was cross-resistant to pyrethrins ( × 34) and eight synthetic pyrethroids also applied topically; least cross-resistance occurred with resmethrin ( × 2.2), bioresmethrin ( × 3.3) and phenothrin ( × 4.0). Generally larger resistance factors were recorded with formulations synergised by piperonyl butoxide (PB). The greatest cross-resistance encountered was with unsynergised tetramethrin ( × 338). Apart from tetramethrin, factors of synergism did not exceed 5.7 with either the susceptible or multi-OP resistant strains. PB antagonised six of the nine pyrethroids against the multi-OP resistant strain. Antagonism also occurred with two of these six, permethrin (cis: trans ratio 1:3) and 5-prop-2-ynylfurfuryl ( 1RS)-cis,trans-chrysanthemate (‘Prothrin’), against the susceptible strain. Considering only formulations without the synergist, the most effective compounds against the susceptible strain, relative to pyrethrins, were bioresmethrin (2.7) and permethrin (2.4). Similarly with the multi-OP resistant strain the most effective compounds were bioresmethrin (28), resmethrin (14) and permethrin (6.6). Thus the LD50 (the dose required to kill 50% of the test species) for bioresmethrin against the resistant strain (0.14 μg) only slightly exceeded the LD50 for pyrethrins against the susceptible strain (0.12 μg).
TL;DR: Close isosteres of fenvalerate [(RS)-α-cyanobenzyl esters, 3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate], in which cyclopropyl groups replace isopropYL have insecticidal activity close to or greater than the parent compounds, and diminished intravenous toxicity to rats are indicated by consistently greater activity of esters from one of an enantiomeric pair of acids.
Abstract: Close isosteres of fenvalerate [(RS)-α-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate], in which cyclopropyl groups replace isopropyl have insecticidal activity close to or greater than the parent compounds, and diminished intravenous toxicity to rats. A direct toxicological relationship of these compounds to fenvalerate itself and to chrysanthemate esters is indicated by the consistently greater activity of esters from one of an enantiomeric pair of acids. Other esters with larger alkyl or cycloalkyl groups, or spiropentane analogues of chrysanthemates are less active insecticides. 13C-Nuclear magnetic resonance spectra suggest that in the α-cyanobenzyl esters there is an intramolecular through-space interaction in solution. The relationships between the chemical structures of the compounds synthesised and their relative activities to different insect species and toxicity to rats are discussed.
TL;DR: Stabilised dust and wettable powder formulations of natural pyrethrins show promising insecticidal effects to certain pest insects.
Abstract: Pyrethroids are more stable to practical conditions when included in β-cyclodextrin, particularly because photodecomposition is reduced. Though inclusion sometimes decreases the contact insecticidal activity, the innate activity is regenerated under conditions which release the free pyrethroids. Stabilised dust and wettable powder formulations of natural pyrethrins show promising insecticidal effects to certain pest insects.
TL;DR: In this article, the (1RS)-cis,trans-3-(2,2-dichlorovinyl)-2, 2-dimethylcyclopropanecarboxylic acid by dehydrohalogenation of 4,6,6.6-tetrahalohexanoates has been modified to produce stereo-selectively the cis-isomer.
Abstract: The synthesis of (1RS)-cis,trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid by dehydrohalogenation of 4,6,6,6-tetrahalohexanoates has been modified to produce stereo-selectively the cis-isomer A new stereospecific synthesis of cis-3-(2,2-dihalovinyl)-2,2-dimethylcyclopropanecarboxylic acids using a bicyclic lactone and its extension to the preparation of the optically active (1R)-cis acid are described
TL;DR: In this article, the authors studied the dissipation rates of diazinon, endosulfan, leptophos, methamidophos and methomyl, parathion and pirimicarb on five minor vegetable crops, including cos and head lettuce, endive, cauliflower and Chinese cabbage.
Abstract: Dissipation rates of diazinon, endosulfan, leptophos, methamidophos, methomyl, parathion and pirimicarb were studied on five minor vegetable crops, including cos and head lettuce, endive, cauliflower and Chinese cabbage. Residues from foliar treatment generally followed an exponential rate of decline. The number of days for residues to drop to below acceptable tolerances was highly dependent on the magnitude of the initial residue; large variations in initial residues were observed between years, between insecticides, and between crop types. Residues of five insecticides and two fungicides used in furrow treatments for onions intended for pickling were determined in the onions at harvest and after pickling. Fensulfothion and fonofos levels were below the accepted tolerance of 0.1 mg kg−1 at harvest, while chlorfenvinphos, chlorpyrifos and ethion were present above this level; fungicide residues were not detected. Following pickling, only ethion residues were still present in the onions at levels greater than 0.1 mg kg−1.
TL;DR: In this article, the preparation of pure (S)-2-hydroxy-2-(3-phenoxyphenyl)acetonitrile (the alcohol component of some very active pyrethroids) was described.
Abstract: The preparation is described of pure (S)-2-hydroxy-2-(3-phenoxyphenyl)acetonitrile (the alcohol component of some very active pyrethroids) from the racemic form of this 2-hydroxyacetonitrile. The new resolution process is based on differences in physical properties of two diastereoisomeric ethers. The resolving agents used are chiral hemiacetal compounds; one of these, 4-hydroxy-6,6-dimethyl-3-oxabicyclo[3.1.0]hexan-2-one, is available from an industrial synthesis of chrysanthemic acid, and appears specially useful for a two-step resolution of many racemic alcohols, even base-sensitive types.
TL;DR: The alkyl phenyl ketone oxime O-benzyl ethers are a new group of insecticidal compounds as mentioned in this paper, which resemble the pyrethroids in general, and the esters of 2-phenylalkanoic acids, in particular fenvalerate, because they show similar physiological effects on isolated nerve preparations and on whole insects.
Abstract: The alkyl phenyl ketone oxime O-benzyl ethers are a new group of insecticidal compounds. Although they lack the ester linkage, they resemble the pyrethroids in general, and the esters of 2-phenylalkanoic acids, in particular fenvalerate, because they show similar physiological effects on isolated nerve preparations and on whole insects; they also show a similar pattern of change of biological activity in response to structural change. The compounds may exist as two geometric isomers, of which only the (E) series shows significant biological activity; this observation appears to have some bearing on the relationship between conformation and activity in the pyrethroid series as a whole.
TL;DR: In this article, a method is described for the analysis of the herbicide bromoxynil and its octanoate in soils Following extraction with aqueous acidic acetonitrile, the octanoates was separated from the phenolic bromioxynil by solvent partitioning The ester and the phenol were assayed by gas-liquid chromatography without further modification or preparation of a derivative Recoveries in excess of 93% were obtained from soils treated with phenol and the ester at levels of 05 or 01 μg g−1.
Abstract: A method is described for the analysis of the herbicide bromoxynil and its octanoate in soils Following extraction with aqueous acidic acetonitrile, the octanoate was separated from the phenolic bromoxynil by solvent partitioning The ester and the phenol were assayed by gas-liquid chromatography without further modification or preparation of a derivative Recoveries in excess of 93% were obtained from soils treated with the phenol and the ester at levels of 05 or 01 μg g−1 The persistence of bromoxynil octanoate applied at a rate of 3 μg g−1 was studied in the laboratory on a heavy clay and a sandy loam at 85% of field capacity moisture and 20°1°C, both alone and in the presence of 2,4-D (2 μg g−1); MCPA (2 μg g−1); MCPA+asulam (both at 2 μg g−1); and MCPA+difenzoquat (both at 2 μg g−1) In each soil there was a rapid conversion of bromoxynil octanoate to the free phenol, which then underwent a rapid degradation, so that after 7 days, over 90% of the original treatment had disappeared There appeared to be no effect on bromoxynil breakdown by any of the herbicides added in combination Small field plots were treated, in early May 1977 and 1978 at two locations in Saskatchewan, with a combination of commercial formulations containing asulam, bromoxynil octanoate, and MCPA at rates of 1 kg ha−1 each After 10 weeks the plots were sampled and analysis showed that in all cases, no asulam, bromoxynil, or bromoxynil octanoate could be extracted from the top 10 cm of soil
TL;DR: A proportion of natural substrate decay in soil is effected by extracellular enzymes tenaciously associated with the humic colloids, and this indigenous catalytic component (‘accumulated’ enzyme) may also be involved in pesticide breakdown, particularly the organophosphorus compounds and the acylanilides.
Abstract: A proportion of natural substrate decay in soil is effected by extracellular enzymes tenaciously associated with the humic colloids. This indigenous catalytic component (‘accumulated’ enzyme) may also be involved in pesticide breakdown, particularly the organophosphorus compounds and the acylanilides, and this possibility is considered here. Additionally, guide-lines for detecting and then confirming the presence of accumulated pesticide-degrading enzymes are suggested.