bluuebunny/crossref_metadata_2025 huggingface dataset:
The actions of formamidine pesticides on identified central neurones of Helix aspersa
Authors: Bokisch Anita J. , Cox Rosalind T. L. , Walker Robert J.
Published: November 2006

Membrane potential and voltage clamp measurements of the responses to octopamine, dopamine, O‐acetylcholine, and the formamidine derivatives chlordimeform (CDM) and N1‐demethylchlordimeform (DCDM) have been made on identified central neurones of Helix aspersa. DCDM and CDM were agonists on both the inhibitory and excitatory octopamine receptors on these neurones but were less potent than octopamine. The direct inhibitory effect of DCDM was antagonised by both phentolamine and cyproheptadine. DCDM was also found to antagonise the effects of octopamine, dopamine and O‐acetylcholine on these neurones. The pA2 values for DCDM against dopamine and O‐acetylcholine were 5.2 (±0.1) and 5.35 (±0.15), respectively. The pA2 value=log[DR‐(1/I)], where I is the concentration of the antagonist, and DR=dose ratio =A2/A1; A1 is the dose of agonist required to produce 50% of the maximum response, and A2 is the dose of agonist needed to produce the same degree of response in the presence of the antagonist. It is concluded that DCDM and CDM act specifically on the octopamine receptors of H. aspersa central neurones, both as agonists and antagonists. The antagonist effect of DCDM against dopamine receptors is probably non‐specific.
Effects of 22,23‐dihydroavermectin B1a on locust (Schistocerca gregaria) muscles may involve several sites of action
Authors: Scott Roderick H. , Duce Ian R.
Published: November 2006

Ibotenic acid [2‐(3‐hydroxyisoxazol‐5‐yl)glycine] induced a dose‐dependent increase in chloride ion conductance in locust muscle fibres which was not sensitive to 4‐aminobutyric acid (GABA). This ibotenate response became rapidly desensitised and appeared to be due to activation of extrasynaptic glutamate H receptors. 22‐23‐Dihydroavermectin B1a (DHAVM) (500 pg to 1 μg ml−1) induced irreversible increases in permeability to the chloride ion and abolished ibotenate responses. DHAVM responses were not altered when glutamate H receptors were desensitised by glutamate (1 mM) or ibotenate (100 μM). Irreversible changes in input conductance caused by DHAVM were not affected by penicillin G (1 mM) or bicuculline (1 mM), but picrotoxin (1 mM) and zinc chloride reduced DHAVM responses by 23.7 and 52.6%, respectively. It is concluded that DHAVM has a number of sites of action on locust muscle that include effects on the glutamate H receptor–chloride ion channel complex, in addition to effects on the GABA receptor–chloride ion channel previously described.
Recent studies on the effects of DDT and pyrethroid insecticides on nervous activity in cockroaches
Authors: Pichon Yves , Guillet Jean Claude , Heilig Ulf , Pelhate Marcel
Published: November 2006

A summary is given of the results of three sets of electrophysiological experiments on the American cockroach (Periplaneta americana). The effects of DDT and S‐bioallethrin [bioallethrin (S)‐cyclopentenyl isomer] on single giant axons were studied using the voltage‐clamp technique. Whereas both molecules induced long tails of inward (sodium ion) current, the voltage and time‐dependency of these tails differed. With DDT, the tail was proportional to the activation of the peak current and decreased with the duration of the pulse, suggesting that the molecules were bound to open sodium channels and delayed their closing. With S‐bioallethrin, the voltage dependency of the tail was different from that of the peak current, and the tail current increased exponentially with the duration of the depolarisation, suggesting that the pyrethroid insecticide modified resting (or silent) sodium channels into slowly activating channels. Modified action potentials, mimicking those produced by the two molecules, were computed on the basis of these results. Deltamethrin, one of the most potent pyrethroid insecticides, was applied topically on a leg mechanoreceptor and was found to have little effect on the local ‘receptor potential’ but to inhibit action potential production. The effects of topical applications of deltamethrin on the dorsal part of the abdomen, on nervous activity in the abdominal connectives, were studied under different experimental conditions. The results suggest that the insecticide molecules diffused rapidly through the cuticle, were concentrated in the haemolymph, and eventually reached the central nervous system, where they inhibited nerve activity.
Effects of topical application of three pyrethroid insecticides on spontaneous activity in sensory nerves of Periplaneta americana and Blabera craniifer
Authors: Heilig Ulf , Pichon Yves
Published: November 2006

Electrophysiological techniques were used to analyse the effects, on the activity in the sensory nerves of Periplaneta americana and Blabera craniifer, after topical applications of three different pyrethroid insecticides: deltamethrin, (1R)‐tetramethrin, and 5‐benzyl‐3‐furylmethyl (E)‐(1R)‐cis‐2,2‐dimethyl‐3‐(2‐oxothiolan‐3‐ylidenemethyl)cyclopropanecarboxylate (RU‐15525; ‘Kadethrin’). The insecticides were applied: (a) to the cercus, and the activity was recorded on the cercal nerve and on the central nervous connectives; or (b) to the last segments of the metathoracic leg, and the corresponding activity was recorded on the crural nerve. In both cases, several categories of receptor were affected but the major part of the recorded activity came from the mechanoreceptors, the functional properties of which were monitored throughout the experiments. In most cases, topical application of small amounts of pyrethroid were found to induce an increase in the spontaneous activity, followed by decrease in excitability. Characteristic differences were, however, found between the three compounds and the effects were concentration‐ and solvent‐dependent. The results were consistent with those obtained from experiments on the sense organs of vertebrates but did not support the idea that the effectiveness of pyrethroid insecticides with an α‐cyanobenzyl group, compared with those without an α‐cyanobenzyl group, originates from a greater effect on the peripheral sensory receptors.
Modelling the economics of controlling Avena fatua in winter wheat
Authors: Cousens Roger , Doyle Christopher J. , Wilson Bernard J. , Cussans George W.
Published: November 2006

A simple mathematical model of the life‐cycle of Avena fatua L. is described and used to consider the financial consequences to the farmer of controlling A. fatua infestations in winter wheat. The likely economic benefits of applying herbicides in different cultivation regimes are investigated. The sensitivity of the model to variations in herbicide performance, straw burning, initial weed infestation and the value of the wheat crop is tested. The model predicts that the highest long‐term benefits will be obtained when a herbicide is applied every time wild oats exceed a density of between 2 and 3 seedlings m−2. Whether or not this results in a significant financial saving over spraying every year depends on the initial level of infestation and on the cultivation method. Whether straw is burnt or not is likely to be of little economic significance.
The effect of the annual use of some pesticides on soil microorganisms, pesticide residues in soil and carrot yields
Authors: Heinonen‐Tanski Helvi , Siltanen Hilkka , Kilpi Sisko , Simojoki Paavo , Rosenberg Christina , Mäkinen Seppo
Published: November 2006

The study deals with the effect of common, annually‐used pesticides on soil microorganisms, pesticide residues in soil, and carrot (Daucus carota) yields in Central Finland. Linuron residues in carrot roots were also analysed. Thiram+lindane and dimethoate were applied from 1973–1981 at the commercially recommended doses on experimental plots of carrots, linuron was applied at twice the recommended rate from 1973–1979 and at the normal rate thereafter and in addition TCA was applied in 1978. Maleic hydrazide was used in the years 1973–1976, and glyphosate after 1977. The numbers of different soil microorganisms, their activities and the pesticide residues were studied from autumn 1978 to 1981. The pesticide treatments reduced the growth of soil algae but increased the total number of microorganisms and the number of aerobic spore‐forming bacteria. Linuron residues in the soil were 0.9–2.8 mg kg−1 in the growing season and 1.2–1.7 mg kg−1 in the autumn, 3 months after application. The residues of glyphosate in the soil were 0.7 mg kg−1 in the autumn, 41 days after the treatment, and had declined to a level of about 0.2 mg kg−1 by the following summer. In the pesticide‐treated plots the carrot yield was only 20–60% of the yield in the hand‐weeded plots. The herbicide programme controlled most of the annual weeds but not couchgrass Elymus repens and milk sow‐thistle Sonchus arvensis.
Factors affecting the biological efficiency of small pesticide droplets against Tetranychus urticae eggs
Authors: Munthali David C. , Wyatt Ian J.
Published: November 2006

Using monosized oil‐based droplets of dicofol against Tetranychus urticae eggs on 1 cm2 discs of bean leaf, the effects of varying droplet diameter (18–146 μm) and concentration of active ingredient (0.5–40 g litre−1) on egg mortality were investigated. A positive curvilinear relationship was found between the spacing of droplets required to produce 50% kill (LS50) and the original diameter of the droplet, D, such that:

where b varied from 0.65 to 1.44 and bore a U‐shaped relationship to concentration. Thus, there was an optimum concentration of about 10 g litre−1, with control efficiency reducing as much as nine times at the extreme concentrations, and even more from the smallest to the largest droplets. The theoretical, practical and economic implications are discussed.
The significance of response time in the detection and measurement of fumigant resistance in insects with special reference to phosphine
Authors: Winks Robert G.
Published: November 2006

The significance of the time of assessment in measurements of fumigant toxicity was examined, using the response of adults of Tribolium castaneum to phosphine. When assessments were made before end‐point was reached, large differences were obtained in mortality levels and in parameters of probit lines fitted to the data. These differences reflected the concentration‐ and dosage‐dependent nature of the speed of action, observed previously with this fumigant. The implications of this in the measurement of resistance were examined. In this instance, comparisons at the same concentration were not greatly affected if seven days or longer had elapsed after exposure. However, it was clear that if different concentrations were used for the susceptible strain and the resistant strain, comparisons made before the end‐point for acute mortality response was reached could be grossly misleading. This is further discussed in the context of some recent reports of phosphine resistance. The results of this study are of significance in assessing the effect of any poison, drug or other stimulus applied to a group of organisms when the time to respond is likely to vary among individuals.
Ultrastructural changes occurring in wheat leaves following triadimefon treatment
Authors: Pring Richard J.
Published: November 2006

Changes occurred in leaf cells following treatment of glasshouse grown wheat seedlings with triadimefon by foliar application, root drench and vapour action. The effects were limited to cells adjacent to stomata, and included damage to the tonoplast and plasmalemma followed by breakdown of chloroplasts. These effects probably resulted from changes in membrane sterols induced by triadimefon treatment. They were severe local reactions, distinct from modification of gibberellin biosynthesis.
Stereochemistry of fluazifop‐butyl transformations in soil
Authors: Bewick David W.
Published: November 2006

Fluazifop‐butyl was incubated with two soils under aerobic conditions at 20°C. Hydrolysis of the racemic herbicidal ester yielded a residue of the corresponding carboxylic acid, fluazifop, in which the R‐enantiomer predominated. Further studies involving the treatment of soil with the separate enantiomers of fluazifop‐butyl showed that the two enantiomers were each hydrolysed with retention of their optical configuration. However, the hydrolysis product with the S‐configuration was inverted (50% inversion in 1‐2 days) to yield, ultimately, a residue of the R‐enantiomer with a high optical purity.
Hydrolysis of cyanazine in aqueous solutions of weak acids
Authors: Grayson B. Terence
Published: November 2006

In the presence of mineral acids or bases the cyano group is the primary point of hydrolysis of cyanazine. However, in solutions of weak acids, carboxylic acids or phenols, the chloro group becomes labile even in essentially neutral solutions. The rates of this catalysed hydrolysis reaction have been determined with a number of carboxylic acids and 2,4‐dinitrophenol. The calculated rates of catalysis follow the Brönsted relationship with a value of ∼0.7. The reaction with 2,4‐dinitrophenol produces an isolatable ether intermediate. Comparison of the rates of hydrolysis catalysed by crotonic acid in deuterium oxide and in water suggests that the mechanism may be of the type specific acid/general base (or nucleophilic) catalysis rather than general acid catalysis.
Absorption, translocation, and metabolism of ethalfluralin and trifluralin in Solanum spp
Authors: Vandeventer John W. , Meggitt William F. , Penner Donald
Published: November 2006

Seedlings of Solanum scabrum Mill. and Solanum ptycanthum Dun. were treated with [14C]ethalfluralin (N‐ethyl‐α,α,α‐trifluoro‐N‐(methylallyl)‐2,6‐dinitro‐p‐toluidine) and [14C]trifluralin (α,α,α‐trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine) supplied in nutrient solution to determine the basis for differences in response by these two species to these two herbicides. Plants of S. scabrum absorbed more [14C]ethalfluralin and [14C]trifluralin than plants of S. ptycanthum. During the first 24 h, S. scabrum seedlings, but not S. ptycanthum seedlings absorbed more [14C]ethalfluralin than did plants treated with [14C]trifluralin. More [14C]ethalfluralin than [14C]trifluralin was found in the shoots of plants of both species. Seventy‐two hours after treatment with [14C]herbicides, the conversion to water‐soluble metabolites was greater for [14C]ethalfluralin than for [14C]trifluralin. In the shoots of plants from both species an average of nearly 55% of the 14C recovered was found in the water‐soluble fraction following [14C]ethalfluralin treatment whereas an average of only 40% was found in the water‐soluble fraction following [14C]trifluralin treatment.
Control of Solenopsis invicta with delayed‐action fluorinated toxicants
Authors: Meer Robert K. Vander , Lofgren Clifford S. , Williams David F.
Published: November 2006

The fire ant, Solenopsis invicta Buren, was accidentally imported into the southern United States and has become a serious medical and agricultural pest of nine southeastern states and Puerto Rico. For a bait toxicant to be effective in fire ant control it must have delayed activity over a wide range of concentrations. Less than 1% of the 7500 compounds screened since 1958 has had delayed action. This paper describes several classes of fluorinated compounds that exhibit delayed activity. These compounds are used to illustrate the following three approaches to the discovery of delayed‐action toxicants: (a) random screening of compounds for delayed action; (b) design of delayed activity through the synthesis of pro‐insecticides; and (c) serendipity. As a result of these investigations two new classes of insecticides were discovered. A compound from one of these classes (tetrahydro‐5,5‐dimethyl‐2(1H)‐pyrimidinone (3‐(4‐(trifluoromethyl)phenyl)‐1‐(2‐(4‐(trifluoromethyl)phenyl)‐ethynyl)‐2‐propenyl‐idene) hydrazone, has been commercialised, while one or more compounds from the second new chemical class (fluorinated sulphonamides) are under development. Fluorinated delayed‐action insecticides have made significant contributions to current fire ant control and will no doubt play a role in the future.
Mechanism of gamma‐HCH resistance in a strain of granary weevil (Sitophilus granarius L.)
Authors: Le Patourel Geoffrey N. J. , Salama Mohamed A.
Published: November 2006

The uptake, accumulation, metabolism and excretion of gamma‐HCH (the gamma isomer of 1,2,3,4,5,6‐hexachlorocyclohexane) by a highly gamma‐HCH‐resistant strain of Sitophilus granarius was studied. It was found that the resistant strain was able to excrete a large proportion of a topically‐applied dose of gamma‐HCH in its frass pellets; under comparable conditions a susceptible strain accumulated a high body load of gamma‐HCH. Neither strain metabolised gamma‐HCH to any significant extent over a 48‐h period after dosing.
Activity of 2‐(1‐alkenyl)‐3‐hydroxy‐1,4‐naphthoquinones and related compounds against Musca domestica
Authors: Jacobsen Niels , Pedersen Lars‐Erik K.
Published: November 2006

A series of 2‐(1‐alkenyl)‐3‐hydroxy‐1,4‐naphthoquinones has been prepared and their toxicities assessed against Musca domestica. By comparison with analogous compounds having saturated 2‐alkyl substituents, or unsaturated substituents with an unconjugated double bond (e.g. lapachol), it was demonstrated that the α‐unsaturation of the substituent is responsible for a significant increase in the toxicity. The effect of the compounds against several other insect species and Tetranychus urticae follows completely different patterns.
Cytological and physiological studies of the effects of IBP on Pyricularia oryzae (II): Effects on apical cells of single hyphae
Authors: Ishizaki Hiroshi , Kobayashi Issei , Kunoh Hitoshi
Published: November 2006

The effects of IBP (S‐benzyl O,O‐diisopropyl phosphorothioate) on tips of single hyphae of Pyricularia oryzae were investigated by interference contrast microscopy. Labelling hyphae with calcofluor white followed by IBP treatment revealed that elongation of apices of almost all hyphae at the colony margin was inhibited after treatment for 4 h. Successive observations on single hyphae of an IBP‐sensitive isolate indicated that apical cells stopped elongating approximately 10 min after the onset of treatment with 2 μg IBP ml−l. Small vacuoles appeared after 50 min; later they increased in number and size, and coalesced, finally producing a chain‐like arrangement of vacuoles in the cytoplasm. When hyphae were treated with 10 μg IBP ml−1, cessation of elongation and vacuolation occurred earlier than when treated with 2 μg ml−1. Apical cells of hyphae of an IBP‐tolerant isolate appeared unaltered even when treated with 10 μg ml−1. These results indicate that a major effect of IBP is to inhibit specifically the growth of apical cells of the IBP‐sensitive isolate.
Biologically active substances from higher plants: Status and future potential
Authors: McLaren James S.
Published: November 2006

Plant breeding and selection, husbandry techniques and crop protection technology, including agrochemicals, have all made substantial contributions to the present‐day level of crop productivity. However, yield losses due to disease, pests and weeds must continue to be minimized in order to meet the food supply demands from an ever growing population. Appropriate synthetic chemicals are becoming increasingly difficult to discover and develop due to stricter requirements on efficacy, selectivity, toxicology and general environmental impact. Consequently, there is a growing interest in understanding and utilising natural mechanisms as the basis for crop protection products. Plants themselves are a rich source of biologically active substances which could potentially be harnessed to modify crop growth or to protect crops against disease and pests. This review describes briefly the current status of understanding relative to plant–plant (herbicide and plant growth substances), plant–fungal (fungicide) and plant–insect (insecticide) interactions. Future prospects are considered in relation to directed synthesis, cell culture, microbial pesticides and plant genetic engineering. The opinion expressed is optimistic and suggests that science today can be utilised to secure the food supply of tomorrow. However, utilising either natural products or molecular biology may require an improved understanding of crop physiology and new developments in agronomy. Therefore, the time‐frame for major impact of the ‘new’ technologies on crop productivity may be longer than is commonly predicted.
Photosensitisers from plants
Authors: Dodge Alan D. , Knox J. Paul
Published: November 2006

The absorption of solar radiation by certain phytochemicals leads to excitation to the singlet state. If unquenched, intersystem crossing occurs, and a longer‐lived triplet state arises. Triplet states may directly induce damage to biological molecules by type I reactions, or by interaction with triplet or ground state oxygen (3O2) generate singlet oxygen (1O2) in a type II reaction.1O2reacts with lipids, proteins and nucleic acids, and thus induces considerable cellular damage if unquenched. Chlorophyll is the most widespread plant photosensitiser, and damage to chloroplasts and plant cells will occur if, for example, photosynthesis is inhibited and excited chlorophyll unquenched. The endogenous formation of chlorophyll precursors from δ‐aminolaevulinic acid fed to darkened leaves has been shown to have a phytotoxic effect in subsequently illuminated plants. In animals a number of breakdown products of chlorophyll, such as phylloerythrin, promote secondary sensitisation, and a condition in sheep known as geeldikkop is induced if these compounds are not metabolised further in the liver. Hypericism is a well‐known case of primary photosensitisation in which the ingested molecule acts as the photosensitiser. The active compound hypericin is produced in the glands of variousHypericumspecies and is offensive to grazing animals and insect predators. Damage is promoted by the photosensitised generation of1O2. A related compound, fagopyrin from buckwheat, is similarly toxic, as also are a number of fungal quinones such as cercosporin. This compound is produced byCercosporaspecies and promotes a leaf‐spot disease in certain crop plants. A large number of furanocoumarins such as psoralen and xanthotoxin are particularly offensive to phytophagous insects. Phototoxicity may involve ultraviolet sensitised binding to DNA as well as type II reactions. Numerous other polyacetylenes and thiophenes are also activated by ultraviolet radiation, and have a role as plant protectants.
The pyrethrins and related compounds. Part XXVIII: Alkenyl‐ and alkynyl‐substituted benzyl esters
Authors: Elliott Michael , Elliott Richard L. , Janes Norman F. , Khambay Bhupinder P. S. , Pulman David A.
Published: November 2006

Over 100 benzyl esters of pyrethroidal acids were synthesised and tested for insecticidal activity to establish detailed structure–activity relationships in compounds with side‐chains similar to those in the natural pyrethrins. Alkenyl, and corresponding alkynyl, side‐chains were effective, both at the 3‐ and 4‐positions, as were side‐chains with extended substitution in either E or Z forms. A cyano group at the α‐position increases activity if the side‐chain is at C‐3, but lowers it drastically if the substituent is at C‐4. Similarly, methyl groups at C‐2 and/or C‐6 may increase activity whether the unsaturated side‐chain is at C‐3 or C‐4, but only in the absence of an α‐cyano group.
The pyrethrins and related compounds. Part XXIX: Haloallylbenzyl esters
Authors: Elliott Michael , Elliott Richard L. , Janes Norman F. , Khambay Bhupinder P. S.
Published: November 2006

Synthesis and bioassay of a series of esters based on pyrethroidal acids established that the activity of halosubstituted allylbenzyl esters depends on the position and stereochemistry of substitution in the allyl side‐chain, on the substitution pattern on benzyl, on the esterifying acid, and, to a lesser extent, on the nature of the halogen substituent itself. The most powerful combination of the first four parameters for activity against houseflies is in (Z)‐3‐haloallylbenzyl esters of the (1R)‐cis 3‐(2,2‐dibromovinyl) acid. Other combinations have moderate to low activity. Some aspects of the variation conform to previously recognised patterns, others define more precisely the requirements for the side‐chain to confer activity. The pattern of response of activity to cyano‐substitution at the α‐position, noted earlier, persists in the current compounds, and is here analysed quantitatively.
The pyrethrins and related compounds. Part XXX: Esters from acids with mono‐halovinyl side chains
Authors: Elliott Michael , Janes Norman F. , Khambay Bhupinder P. S.
Published: November 2006

Esters of 3‐phenoxybenzyl alcohol and its α‐cyano derivative with 2,2‐dimethylcyclopropanecarboxylic acids bearing (E)‐ or (Z)‐3‐monohalovinyl side chains (haloiodo, bromo, chloro or fluoro) were synthesised and had moderate to high insecticidal activities, but these were generally lower than those of established pyrethroids with the corresponding 3‐(dihalovinyl) side chains. Compounds with 3‐(2‐chloroprop‐1‐enyl) side chains were intermediate in potency between the related chrysanthemates and 3‐(dichlorovinyl) esters.
Studies on the mode of action of asulam, aminotriazole and glyphosate in Equisetum arvense L. (field horsetail). I: The uptake and translocation of [14c]asulam, [14C]aminotriazole and [14C]glyphosate
Authors: Marshall George , Kirkwood Ralph C. , Martin David J.
Published: November 2006

The uptake and translocation of [14C]asulam (methyl 4‐aminophenyl‐sulphonylcarbamate), [14C]aminotriazole (1‐H‐1,2,4‐triazol‐3‐ylamine) and [14C]glyphosate (N‐(phosphonomethyl)glycine) were assessed in Equisetum arvense L. (field horsetail), a weed of mainly horticultural situations. Under controlled‐environment conditions, 21°C day/18°C night and 70% r. h., the test herbicides were applied to 2‐month‐old and 2‐year‐old plants. Seven days following the application of 0.07‐0.09 °Ci (1.14mg) of the test herbicides to young E. arvense, the accumulation of 14C‐label (as percentage of applied radioactivity) in the treated shoots, untreated apical and basal shoots was as follows: [14C]asulam, 13.2, 0.18 and 1.02%; [14C] aminotriazole, 67.2, 3.65 and 1‐91%; [14C]glyphosate, 35.9, 0.06 and 0.11%. The equivalent mean values for the accumulation of 14C‐label in 2‐year‐old E. arvense were [14C]asulam, 12.0, 1‐15 and 1.74%; [14C]aminotriazole, 58.6, 9.44 and 4.12%; [14C]glyphosate, 33.1, 0.79 and 2.32%. In the latter experiment, test plants received 0.25‐0.30 °Ci (4mg) of herbicide, they were assessed after a 14‐day period and the experiment was carried out at 3‐week intervals between 2 June and 25 August on outdoor‐grown plants. Irrespective of test herbicide or time of application, very low levels of 14C‐label accumulated in the rhizome system. Only 0.2% of the applied radioactivity was recovered in 2‐year‐old plants and 0.4% in 2‐month‐old plants. In the young plants [14C]asulam accumulated greater amounts and concentrations of 14C‐label in the rhizome apices and nodes than [14C]aminotriazole or [14C]glyphosate treatments. Inadequate control of E. arvense under field conditions may be due to limited basipetal translocation and accumulation of the test herbicides in the rhizome apices and nodes.
Acaricidal 1,2,4,5‐tetrazines
Authors: Brooker Peter J. , Parsons John H. , Reid Jim , West Peter J.
Published: November 2006

A series of 1,2,4,5‐tetrazines has been synthesised and screened for acaricidal activity. Laboratory tests have shown several of the compounds to be highly active mite ovicides. Further examination in the field has identified a highly active compound, which gives prolonged control of mites on top fruit. The selected compound (clofentezine) is shown to be safe to mite predators and beneficial species and has been developed commercially for use on top fruit. (Clofentezine is the B.S.I. approved common name of 3,6‐bis‐(2‐chlorophenyl)‐1,2,4,5‐tetrazine).
Synthesis and insecticidal activity of lipophilic amides. Part 2: Effect of heteroatom replacements and of introducing methyl groups in the pentadiene system
Authors: Elliott Michael , Farnham Andrew W. , Janes Norman F. , Johnson Diana M. , Pulman David A.
Published: November 2006

Following the discovery of insecticidal activity in (2E,4E)‐N‐(2‐methylpropyl)‐6‐phenylhexa‐2,4‐dienamide, structural analogues containing variations of the central pentadiene system have been examined. They include the five compounds with extra methyl groups on each of the five carbons in turn, and compounds in which heteroatoms have been introduced instead of, or additional to, the original CH or CH2 groups. All were insecticidally inactive, indicating for the first time the severe limitations on this group if activity is to be retained.
Synthesis and insecticidal activity of lipophilic amides. Part 5: Influence on activity of varying the substituent on nitrogen
Authors: Elliott Michael , Farnham Andrew W. , Janes Norman F. , Johnson Diana M. , Pulman David A.
Published: November 2006

Isomerisation or shortening of the 2‐methylpropyl group in (2‐methylpropyl)‐6‐phenylhexa‐2, 4‐dienamide lowers insecticidal activity, as does methylation at nitrogen. Methylation at each carbon atom in turn, and, within limits, in combination, gives compounds with substantial, sometimes increased, activity. Cyclic and olefinic equivalents of the effective alkyl substituents are mostly less active.
Gas‐liquid chromatographic determination of NDMA in dimethylamine and in laboratory prepared herbicidal dimethylamine formulations
Authors: Wigfield Yuk Y. , McLenaghan Charles C.
Published: November 2006

A method is described for the analysis of trace levels of N‐nitroso‐dimethylamine (NDMA) in anhydrous and in 60% (w/w) aqueous dimethylamine (DMA). Anhydrous DMA was converted to 60% (w/w) aqueous DMA, which was diluted with absolute ethanol and analyzed by a gas‐liquid chromatograph coupled to a thermal energy analyzer (g.l.c./t.e.a.) for the presence of NDMA. Experiments showed that NDMA was not generated in the g.l.c. injection port during analysis. The NDMA contents in seven samples of aqueous DMA and four samples of anhydrous DMA ranged from 55.0 μg −1 of 60% (wlw) aqueous sample to non‐detectable levels. The minimum detectable amount was 40 pg, which corresponds to 0.1 μg g−1. Anhydrous DMA was found to contain the lowest level of NDMA. 2, 4‐Dichlorophenoxyacetic acid (2, 4‐D), 4‐chloro‐2‐methylphenoxyacetic acid (MPCA) and 3, 6‐dichloro‐ 2‐methoxybenzoic acid (dicamba) were formulated with 60% (w/w) aqueous DMA into the corresponding DMA salts. The resulting herbicides were analyzed for NDMA, the levels of which were compared with the initial levels present in the 60% (w/w) aqueous DMA. Heating and stirring during formulation were found to be the main factors causing increased levels of NDMA.
N‐Nitrosodimethylamine content of aqueous dimet hylamine and phenoxy herbicide/dimethylamine formulations during storage
Authors: Wigfield Yuk Y. , McLenaghan Charles C.
Published: November 2006

N‐Nitrosodimethylamine (NDMA) levels in samples of 600 g litre−1 aqueous dimethylamine (DMA) solution stored at 4, 25 and 40°C, in formulations of the DMA salt of 2, 4‐dichlorophenoxyacetic acid (2, 4‐D) and of the DMA salt of 4‐chloro‐2‐methylphenoxyacetic acid (MCPA) at 40°C were monitored using a gas‐liquid chromatograph coupled with a thermal energy analyser (g.l.c./t.e.a.). The NDMA content of aqueous DMA at 4°C increased from 0.32μgg−1 to 8.6μgg−1 in 156 days. At 25°C it increased from 0.20μgg−1 to 10.5 μgg−1 in 156 days and at 40°C from 0.76μgg−1 to 7.12μgg−1 in 54 h. At 40°C, the NDMA in the 2, 4‐D/DMAsalt increased from 0–53μgg−1 to 2.79μgg−1 in 96 days and in the MCPA/DMA salt from 0.48μgg−1 to 5.51 μgg−1 in 21 days.
Permethrin treatments in canadian forests. Part 2: Impact on stream invertebrates
Authors: Kreutzweiser David P. , Kingsbury Peter D.
Published: November 2006

A series of experiments was conducted between 1977 and 1981 to evaluate the effects of aerially applied permethrin on forest stream invertebrates. All permethrin applications to forest streams resulted in large drift increases, and most produced measurable reductions in benthos density. Recovery of benthic fauna following the various permethrin applications was apparent from 1 to 18 months post‐spray. In double‐application experiments, the second treatments reduced benthos density to a point at which recovery of numbers was slower than after the impact resulting from a single application of the same dosage.
Phloem translocation of weak acids in ricinus communis
Authors: Rigitano Renê L. O. , Bromilow Richard H. , Briggs Geoffrey G. , Chamberlain Keith
Published: November 2006

Uptake of weak acids by roots of Ricinus communis and their translocation to shoots increased as the pH of the nutrient solution decreased, the behaviour being closely similar to that observed for the same compounds in barley. Phenoxyacetic acids (p Ka ˜3) with log Kow, for the undissociated acid of between 1 and 3 were readily taken up and translocated in phloem to the apical leaf and the upper stem of R. communis following injection into the petioles of mature leaves; strong retention of these chemicals in the stem rapidly depleted their concentration in phloem down the stem so that very little was found in roots. A more polar and a more lipophilic phenoxyacetic acid were poorly translocated from the petioles, and flamprop (pKa 3.7, log Kow, 2.9) was predominantly xylem‐mobile. Maleic hydrazide (pKa 5.65, log Kow, −0.6) was taken up from the petioles rather slowly but was readily phloem‐translocated from the mature leaves, and little was retained by the stem, permitting appreciable amounts to reach the roots and nutrient solution. Concentrations of these weak acids in leaf phloem were up to ten times higher than in the adjacent leaf cells, and could be predicted reasonably well assuming that accumulation in phloem was purely a physico‐chemical process occurring due to the ion‐trap effect, taking values obtained from barley roots for the ratio of the permeabilities of membranes to the undissociated and dissociated forms of the acids.
Triapenthenol—a new plant growth regulator
Authors: Lürssen Klaus , Reiser Wolf
Published: November 2006

Triapenthenol is the proposed common name for a new plant growth regulator (E)‐l‐cyclohexyl‐4, 4‐dimethyl‐2‐(1, 2, 4‐triazol‐l‐yl)‐l‐penten‐3‐01. Its main influence upon plants is an inhibition of shoot growth. Root growth is not inhibited at normal dosages. Growth inhibition in dicotyledons is achieved by either foliar or root uptake, while in monocotyledons, root uptake is necessary and foliar treatment fails to produce growth inhibition. Mainly acropetal transport of the compound is assumed to be responsible for this behaviour. Apart from growth inhibition, a marked influence upon water relations in plants was observed. In barley, water consumption was reduced for whole plants. Calculations also revealed a reduction of transpiration per unit leaf area. In rape only an initial reduction of water consumption was observed. The fresh weight/dry weight ratio of plants was increased by the compound. The total nitrogen content per plant was unchanged but increased when calculated on a dry weight basis. The compound exerted retardant effects by interfering with gibberellin biosynthesis, but the shape of the dose‐response curves with increasing gibberellin concentrations in the presence and in the absence of triapenthenol suggests that this may not be the only effect of the compound on the plant metabolism.
Persistence of carbendazim in field‐grown soybeans following application of thiophanate‐methyl fungicide
Authors: Lyons Philip C. , Lyda Stuart D.
Published: November 2006

Carbendazim was quantified spectrophotometrically in leaves, petioles, stems and pods from upper and lower halves of entire soybean plants following one or two foliar applications of thiophanate‐methyl fungicide (1.1 kg ha−1 a.i.). Following the first application, the highest carbendazim concentrations occurred 1‐4 days post‐application and declined thereafter to undetectable (⩽0.12 mg kg−1) or barely detectable levels by day 26. The highest concentrations were in the leaves where carbendazim levels exceeded 3.5 mg kg−1 on day 4 and remained above 1.0 mg kg−1 until day 19. Concentrations in petioles and upper pods were initially in excess of 1.0 mg kg−1 and remained above 0.5 mg kg−1 for 12 days. In lower pods and in stems, concentrations were very low and often not detectable. Typically, concentrations were higher in samples from the upper half of the plant than in those from the lower half. A second application on day 18 resulted in carbendazim concentrations similar to those immediately after the first application; however, concentrations declined rapidly coincidentally with a period of rain. This decline may have been facilitated by poor fungicide uptake due to senescence of the plants.
Hydrolysis of 1, 3‐dichloropropene in dilute aqueous solution
Authors: McCall Philip J.
Published: November 2006

Hydrolysis of [14C]‐radiolabeled 1, 3‐dichloropropene (1, 3‐D) was studied at pH 5, 7 and 9 at 10, 20 and 30°C in sterile buffered water. The rate of hydrolysis was independent of pH at each temperature, with measured half‐lives of 3‐1 (±0.l), 11.3 (±0.5) and 51 (±2.3) days at 30, 20 and 10°C, respectively. The activation energy for the hydrolysis reaction was determined to be 23.9 kcal mol−1 deg−1. One hydrolysis product was formed during the course of the study and was identified by co‐chrornatography with analytical standards, using h.p.l.c., to be 3‐chloroallyl alcohol. The alcohol appeared to be stable to further hydrolytic conversion and was formed in the same cis: trans ratio as in the initial 1, 3‐D starting material, indicating essentially identical rates of hydrolysis for the cis and trans isomers of 1, 3‐D.
Factors affecting the foliar absorption and redistribution of pesticides. 1. Properties of leaf surfaces and their interactions with spray droplets
Authors: Stevens Peter J. G. , Baker Edward A.
Published: November 2006

Foliar uptake into eleven plant species, grown under controlled environment, has been determined for spray deposits of glyphosate, 2, 4‐D and prochloraz applied as solutions in aqueous solvents in the presence and absence of an ethoxylated nonylphenol surfactant. Over 24 h, uptake of glyphosate did not exceed 6% of applied chemical into any species whereas uptake of 2, 4‐D and prochloraz differed between species and was modified significantly by the addition of surfactant. Uptake of prochloraz was increased consistently by adding surfactant, but the response of 2, 4‐D was variable. Increased uptake was attributed mainly to surfactant‐enhanced wetting of the leaf surfaces. Uptake of prochloraz per unit wetted area increased in the presence of surfactant but that of 2, 4‐D decreased. Uptake of either chemical did not correlate with the presence of specialised leaf surface structures, cuticular morphology or distribution of the chemicals within the dried deposits. The dried chemicals were distributed either uniformly or as annuli as a result of complex interactions between the active ingredient, surfactant and the leaf surfaces. Regression analysis indicated that the epicuticular wax and cuticular membrane were the major sinks for both 2, 4‐D and prochloraz during the 24‐h period.
Fumigant residues in wheat and other cereal grains resulting from the use of 1,1,1‐trichloroethane and bromomethane as a liquid fumigant mixture
Authors: Scudamore Keith A.
Published: November 2006

The sorption of 1,1,1‐trichloroethane on wheat, barley and oats during fumigation and its subsequent loss during airing has been studied after treatment with 1,1,1‐trichloroethane alone or in a mixture with bromomethane. The extent of sorption of bromomethane and the amount of inorganic bromide formed from reaction of bromomethane with constituents of the grain samples were not affected by the presence of 1,1,1‐trichloroethane. The sorption of 1,1,1‐trichloroethane on cereal grains and the amount of inorganic bromide formed increased with commodity moisture content. Bromide formation also increased with temperature and varied both with the cereal and with different varieties of wheat tested. At low dosage levels, residues of 1,1,1‐trichloroethane were proportional to concentration times; time (CT product) but at the highest dosage used residues were disproportionately higher than expected, owing to vapour concentration approaching saturation pressure. The rate of loss of 1,1,1‐trichloroethane from wheat, barley and oats under controlled conditions was found to be more dependent on the storage time than on the residue remaining or the original level of treatment. For wheat, initial sorption of 1,1,1‐trichloroethane varied with variety and to a lesser extent also varied between different samples of a single variety tested. However, the rate of airing appeared to be similar for all samples of wheat tested. Results are also described showing the effects on airing rates induced in wheat in which the moisture content was also changing. These results suggest that, in wheat in which moisture content increases during storage, the residue at a specific time after treatment would not be particularly dependent on the interim conditions while in wheat of falling moisture content, residues would very much depend on the conditions prevailing. A knowledge of these effects should help to refine attempts to extrapolate results of laboratory studies to commercial scale treatments.
Excretion, distribution and depletion of [14C]cypermethrin and cis and trans isomers of 3‐(2,2‐dichlorovinyl)‐2,2‐dimethylcyclopropanecarboxylic acid administered orally to laying hens
Authors: Akhtar M. Humayoun , Hamilton Robert M. G. , Trenholm H. Locksley
Published: November 2006

Radiolabelled racemic cypermethrin, and the cis and trans isomers of 3‐(2,2‐dichlorovinyl)‐2,2‐dimethylcyclopropanecarboxylic acid (labelled at C‐1 of the cyclopropane ring) were each separately administered orally in feed for three consecutive days to White Leghorn laying hens. The amount of individual compound dosed was approximately 7.5 mg per hen per day. Radiocarbon was eliminated very rapidly in excreta. Tissue residues were generally very low with the exception of fat depots, but trace amounts of radiocarbon residues were still detectable in fat, liver and kidney 11 days post‐treatment. Residues were detected in the egg albumen of hens treated with cypermethrin and cis isomer of the acid, but none was detected from trans acid. Metabolites identified included products arising from the hydrolysis of the ester bond of cypermethrin, followed by oxidative attack on one or both methyl groups. The rate of oxidative attack on methyl groups was influenced by the geometry of the dichlorovinyl group. On the basis of the metabolites identified a metabolic pathway for cypermethrin in laying hens was proposed which included hydrolysis of the ester bond followed by oxidation of methyl group(s). The data indicate that use of cypermethrin as recommended should not produce residues in eggs and meat of laying hens at levels that are of toxic concern.
Studies on pesticides based on coumarin. I. Antifungal activity of 6‐alkyl‐3‐n‐butyl‐7‐hydroxy‐4‐methylcoumarins
Authors: Singh Rajvir , Gupta Bharat B. , Malik Om P. , Kataria Hans R.
Published: November 2006

Seven 6‐alkyl‐3‐n‐butyl‐7‐hydroxy‐4‐methylcoumarins and three other related substituted coumarins were synthesised, characterised and tested for their toxicity towards mycelial growth of seven phytopathogenic fungi in culture. Rhizoctonia solani, Alternaria alternate, and Drechslera oryzae exhibited maximum sensitivity to these compounds whereas Pythium aphanidermatum, Colletotrichum falcatum, Fusarium solani and Macro‐phomina phaseolina were less sensitive. The 6‐n‐butyl and 6‐n‐pentyl derivatives possessed strongest toxicity towards all fungi except C. falcatum but the corresponding 6‐n‐propyl derivative was inhibitory to only D. oryzae and A. alternata.
A study of the trans‐esterification products of malathion by capillary gas chromatography‐mass spectrometry
Authors: Wilkins John P. G. , Mason David J.
Published: November 2006

The organophosphorus insecticide malathion undergoes trans‐esterification reactions with many simple alcohols under mild conditions. The products of a series of such reactions were prepared and characterised by capillary gas chromatography‐mass spectrometry. For the trans‐esterification reaction of malathion with a given alcohol, the mass spectra of the two initial products indicated that they were formed by exchange of one or other of the two non‐equivalent ethoxy groups of the succinate moiety of the malathion molecule. The mass spectra were not sufficiently diagnostic to allow the site of trans‐esterification for each product to be assigned. Synthesis and13 C‐nuclear magnetic resonance spectroscopy were used to show that the major initial product is formed by trans‐esterification of the β‐carboxylate group of the succinate moiety. The two methoxy groups of the phosphorodithioate ester moiety exchange much less readily and, in the alcohols examined, such exchange was only apparent with ethanol. Gas chromatographic retention times and mass spectral data for the series of trans‐esterification products examined are presented and discussed. The data and techniques presented provide a means of determining trace amounts of malathion α‐ and β‐monoacids, which are important metabolites of malathion, after their conversion to a suitable ester (the monoacids themselves were not amenable to gas chromatographic analysis under the conditions described).
Factors influencing the selective toxicity of cis‐ and trans‐cypermethrin in rainbow trout, frog, mouse and quail: Biotransformation in liver, plasma, brain and intestine
Authors: Edwards Robert , Millburn Peter , Hutson David H.
Published: November 2006

The biotransformation rates of cis‐ and trans‐cypermethrin, and their routes of metabolism have been studied in subcellular tissue fractions from rainbow trout, frog, mouse and quail to assess the role of detoxification in the selective toxicity of pyrethroid insecticides in these species. The liver was the principal site of biotransformation in mouse and quail, though intestine and plasma (not quail) were also active in hydrolysing cypermethrin isomers. In trout, plasma and intestine were more important sites than liver for the detoxification of tram‐cypermethrin. On the basis of total metabolism of cypermethrin isomers by liver per kilogram of body weight, mouse, quail and frog were respectively 27, 17 and 2 times more active than trout towards the cis‐isomers, and 87, 55 and 6 times more active in metabolising the trans‐isomers. Some of these differences were accounted for by variations in liver/body weight ratios. Extra‐hepatic tissues metabolised cypermethrin principally by ester hydrolysis with maximal activity towards the trans‐isomers, brain and gut contents possessing very low activities. In the presence of NADPH and UDPGA, cis‐ and trans‐cypermethrin were metabolised at very similar rates in frog, mouse and quail liver. Trout liver was more active towards the cis‐isomer forming 4′‐hydroxycypermethrin (aryl hydroxylation) and its glucuronide almost exclusively. Frog and mouse showed either aryl hydroxylation or aliphatic hydroxylation of one of the methyl groups at C‐2 of the cyclopropane ring of cis‐cypermethrin, while quail was unique amongst the four species in metabolising the cis‐isomers largely by oxidative de‐esterification. In all species, except trout, trans‐cypermethrin was rapidly hydrolysed by micro‐somal esterases. The presence of the phase II cofactor UDPGA increased the rate of biotransformation mainly through the glucuronidation of the products of oxidation. This investigation shows that, in addition to differences in target organ sensitivity, biotransformation accounts for some of the observed differences in the susceptibility of these four species to pyrethroids.