bluuebunny/crossref_metadata_2025 huggingface dataset:
A leaf surface scanning technique using a fluorescence spectrophotometer for the measurement of spray deposits
Authors: Furness Geoffrey O. , Newton Mark R.
Published: November 2006

Fluorescent pigment deposits on sprayed plant surfaces were measured using a fluorescence spectrophotometer to which a surface scanning device was fitted. Quantities of water‐ and oil‐suspended fluorescent pigments deposited on citrus leaves, measured by this technique, were similar to those measured using two direct chemical methods. With artificially applied droplets and a constant quantity of pigment per unit area, changing the droplet size and pigment concentration made little or no significant difference to fluorimetry readings.

With surface scanning, the number of samples and time required to detect significant differences in pigment deposits between sites, and within and between treatments, was reduced compared to other methods, and it was possible to measure the variability of the deposit across a single leaf surface, as well as the mean quantity of pigment deposited per unit area. The suitability of different types of fluorimeter for quantitative measurements of spray deposits on plant surfaces is also discussed, this being the most important factor in reducing the number of samples and time required.
Studies involving avermectin and the 4‐aminobutyric acid (GABA) receptor of Ascaris suum muscle
Authors: Holden‐Dye Lindy , Hewitt Graham M. , Wann Kenneth T. , Krogsgaard‐Larsen Povl , Walker Robert J.
Published: November 2006

This study describes the pharmacology of the Ascaris suum muscle GABA receptor using a range of GABA agonists and antagonists. The GABA receptor at this site does not readily fit into GABA‐A or GABA‐B classification. The effect of the potent anthehmintic, avermectin, on these cells was investigated. It was found to inhibit GABA‐evoked increase in membrane conductance and membrane hyper polarisation on quiescent muscle cells with an apparent affinity constant in the mid‐micromolar range. When applied to spontaneously active muscle cells, avermectin (I üM) inhibited the spiking activity after a delay of about 25 min.
The discovery and development of fungicides—does biochemistry have a role?
Authors: Kuhn Paul J.
Published: November 2006

While the parts played by synthesis chemists, biologists and toxicologists in the discovery and development of fungicides are well established, the role of the biochemist is generally less well appreciated. Biochemistry does, however, have an important contribution to make, the principal activities being: mode of action studies; generation of data on the intrinsic activities of molecules; biorational design of novel inhibitors; fungicide resistance; and molecular biology and its applications. The background to each of these areas and relevance to fungicide discovery and development are described. Examples from studies on ergosterol biosynthesis inhibitors are used to illustrate the discussion.
Synthesis and in‐vitro antifungal activity of 6‐trifluoromethylpyrazolo[3,4‐d]pyrimidines
Authors: Poli Tiziana , Vicentini Chiara B. , Brandolini Vincenzo , Veronese Augusto C. , Manfrini Maurizio , Guarneri Mario , Giori Paolo
Published: November 2006

Thirty 6‐trifluoromethylpyrazolo[3,4‐d]pyrimidines were synthesised and tested for antifungal activity in vitro against ten phytopathogenic fungi of different taxonomic classes. Six of the compounds had noteworthy activity against Sclerotinia minor, Corticium solani and Phoma betae. The relationships between structure and activity are discussed on the basis of the present and previous studies.
The chemical control of the lesser date moth, Batrachedra amydraula meyr., and residue levels of organophosphate insecticides in dates
Authors: Al‐Samarraie Adnan I. , Al‐Hafdh Emad , Abdul‐Majed Khloud , Basumy Mabrouk A.
Published: November 2006

Larvae of the lesser date moth (Batrachedra amydraula Meyr.) cause damage to dates in Iraq. A formulation based on a mixture of equal parts of wheat flour and pollen grains and containing either chlorpyrifos, fenitrothion or pirimiphos‐methyl (all at 5 mg kg−l) was dusted (5 g formulation bunch−1) onto female clusters of dates at the time of pollination. Numbers of larvae, yield of dates and insecticide residues were monitored over a three‐month period. Results showed that, by this technique, all three insecticides were effective in controlling the pest but that fenitrothion and chlorpyrifos were better than pirimiphos‐methyl.
The metabolism of tefluthrin in the goat
Authors: Heath Jeramy , Leahey John P.
Published: November 2006

A goat was dosed orally with [14C]tefluthrin, twice daily for 4 days, at a rate equivalent to 10.9 mg kg−1 in its diet. Within 16 h of the final dose, 70.1% of the dose had been excreted (urine 41.4%, faeces 28.7%). Extensive metabolism occurred in the goat by ester cleavage and oxidation at a variety of positions on the molecule. Low radioactive residues were detected in the milk (0.076 mg kg−1), fat (0.076 mg kg−1) and muscle (0.016 mg kg−1), with tefluthrin as the largest individual component of the residue (milk 66.5%, fat 76.7%, muscle 34.2%). Higher residues were present in the kidney (0.3 mg kg−1) and liver (1.0 mg kg−1) and only a small percentage of this residue was due to tefluthrin (kidney 3.4%, liver 6.1%). The remainder of the residue in the kidney and liver was a complex mixture of metabolites. Most of the kidney metabolites were identified, but a high proportion of the liver residue was due to six unidentified polar compounds.
Development of a nephelometric version of the CIPAC method for measuring dilute emulsion stability
Authors: Hill Alistair C.
Published: November 2006

The characterisation of emulsions at dilution rates greater than 1:20, currently used in most international specifications for agrochemical emulsifiable concentrate (EC) formulations, is becoming increasingly important. CIPAC MT36.2 is the internationally‐accepted test method for determining the bulk stability of emulsions containing 10 ml litre−1 or less of added EC. A new nephelometric version of this test method has been examined which, although not as accurate as the official method, gives more rapid results. An assessment of the new method against the official method at a working concentration of 5 ml litre−1 is reported. Agreement is good, despite the semi‐empirical nature of the new method, but only if emulsions are re‐emulsifiable at the end of the standing period. The scope of the method is discussed and areas of application indicated.
A mixed function oxidase factor contributing to permethrin and dichlorvos resistance in Lycoriella mali (fitch) (diptera: Sciaridae)
Authors: Brewer Kathy K. , Keil Clifford B.
Published: November 2006

Several observations suggested that enhanced mixed function oxidase (MFO) activity was one of several factors contributing to permethrin and dichlorvos resistance in the mushroom pest, Lycoriella mali (Fitch) (Diptera: Sciaridae). This was investigated using the mixed function oxidase inhibitor, piperonyl butoxide (PBO), in topical application bioassays with reference and field‐selected resistant strains. At the LD50, strains of resistant colonies (AV1, AV2, TK1) used in this study were 41‐(AV1), 34‐(AV2), and 62‐fold (TK1) resistant to permethrin, relative to the reference strain (ONT9). Permethrin in the reference strain was only synergized 2‐ (ONT9) and 4‐ (ONT13) at the LD50. Synergist ratios for resistant strains were 12 (AV1), 34 (AV2) and 94 (TK1) at the LD50. Moderate dichlorvos resistance was twice documented in the AV strain. Resistance ratios of 37 (AV4) and 52 (AV9) were observed at the LD50, relative to the reference strain (ONT10). Dichlorvos was synergized only 2‐fold at the LD50 in the reference strain (ONT10). However, PBO abolished dichlorvos resistance in the AV9 strain. The effectiveness of PBO in these studies indicated that enhanced MFO activity was present in resistant L. mali from southeastern Pennsylvania. Resistance to DDT (54‐fold at the LD50) was also documented. Other factors, such as an altered target site (kdr), may also have contributed to control failures with permethrin.
Prospects for strain improvement in entomopathogenic fungi
Authors: Heale James B. , Isaac Jane E. , Chandler David
Published: November 2006

The deployment of entomopathogenic fungi for the control of insect pests offers an environmentally‐acceptable strategy. Major obstacles to their application include variability in effectiveness due to uncontrolled environmental parameters (temperature, humidity) and development of suitable formulation techniques. Strains differ considerably in genetic ability to cause mortality and to spread within populations. Pathogenicity is the result of the interaction of numerous individual traits determining germination and penetration, followed by successful growth within the target host, which is a prerequisite for induction of mortality. No effective singlegene determined toxin has been reported for entomopathogenic fungi, but the application of gene cloning techniques for specific proteases is a likely future development. Genetic manipulation techniques, designed to recombine complex traits associated with pathogenicity via the parasexual cycle, are described here in relation to successful steps achieved in strain improvement programmes which involve: (a) Verticillium lecanii (Zimm.) Viegas against the glasshouse whitefly: Trialeurodes vaporariorum and the aphid Macrosiphoniella sanborni; (b) Metarhizium anisopliae (Metsch.) Sorokin against the rice brown planthopper Nilaparvata lugens.
Insecticide resistance: Research and management
Authors: Brattsten Lena B.
Published: November 2006

This introductory paper to the Rutgers Symposium outlines the background of the development of resistance to insecticides and discusses various aspects of the problem in the context of modern agrochemical practice. Resistance can only be countered by properly mounted management programmes, but the successful design and implementation of these requires a thorough understanding of the fundamental processes involved, and the importance of continuing research into these is stressed.
Molecular neurobiology: Implications for insecticide action and resistance
Authors: Soderlund David M. , Bloomquist Jeffrey R. , Wong Fulton , Payne Lori L. , Knipple Douglas C.
Published: November 2006

Recent advances in molecular neurobiology have provided an unprecedented insight into the structure and function of the three principal target sites for neurotoxic insecticides: acetylcholinesterase, the 4‐aminobutyric acid (GABA) receptor–chloride ionophore complex, and the voltage‐sensitive sodium channel. This paper reviews some of these advances and their current or potential application to problems in insecticide resistance. It particularly emphasizes studies of the molecular biology of voltage‐dependent sodium channels in the context of resistance to DDT and pyrethroids resulting from reduced neuronal sensitivity.
Resistance to synthetic pyrethroids in the bollworm, Heliothis armigera from Andhra Pradesh, India
Authors: McCaffery A. R. , King A. B. S. , Walker A. J. , El‐Nayir H.
Published: November 2006

Helio this armigera collected in October 1987 from Juzzuru in the coastal cotton growing district of Krishna in Andhra Pradesh (Eastern India) were highly resistant to cypermethrin and fenvalerate and moderately resistant to endosulfan. Prior to this, in 1986, H. armigera in the Hyderabad area were resistant to DDT but not to pyrethroids or endosulfan. By late 1987 these latter populations were highly resistant to pyrethroids and mildly resistant to endosulfan. Concurrently, the resistance to DDT increased. It is suggested that resistant moths from the east coast migrated downwind in a northwesterly direction with the prevailing winds which occur at that time of year. The level of pyrethroid resistance in H. armigera infesting pigeon‐pea and chick‐pea fields around Hyderabad increased steadily up to March 1988. These results are discussed with special reference to the resistance mechanisms likely to be involved.
Laboratory evaluation of the toxicity of 1,3‐di(methoxycarbonyl)prop‐l‐en‐2‐yl dimethyl phosphate (‘Bomyl’) and methomyl to susceptible and multi‐resistant strains of houseflies (musca domestica L.)
Authors: Barson Graham
Published: November 2006

The toxicity of 1,3‐di(methoxycarbonyl)prop‐l ‐en‐2‐yl dimethyl phosphate (‘Bomyl’) to female houseflies (Musca domestica L.) was compared with that of the carbamate insecticide methomyl. Insecticide‐susceptible (Cooper) and multi‐insecticide‐resistant (G and GIV) strains of flies were tested by exposure to granular bait and by topical application of technical formulations. Females from G and GIV strains were shown to be resistant to bomyl and methomyl, and resistance levels were related to the insecticide and test method used. Resistance ratios for bomyl and methomyl were low for the GIV strain when the toxicants were applied topically, being x6.1 and x 9.3 respectively at the LD95 level, but when sugar granules were coated with the insecticides and fed to flies, the resistance ratios were higher at x 43.0 and x 15.6. Flies from the resistant G strain were also shown to be resistant to the granular bait formulations of bomyl and methomyl when the granules were scattered or suspended from treated bait targets. A small proportion of flies from the resistant G and susceptible strains recovered from knockdown after feeding on methomyl granules, but most of these had lost their ability to fly. There was no significant recovery of flies in any of the bomyl tests. The feeding responses of individual female flies to scattered bomyl granules was also studied. Flies from the resistant G strain took significantly longer than susceptible flies to initiate a feeding response (P<0.001). Once feeding had commenced there was no difference between the strains in the time spent.
The occurrence of pesticide residues in UK home‐grown and imported wheat
Authors: Osborne Brian G. , Barrett Gillian M. , Laal‐Khoshab Alireza , Willis Kenneth H.
Published: November 2006

Residue levels of organophosphorus, organochlorine and carbarmate insecticides, urea, carbamate and anilide herbicides, carbendazim, fumigants and bromide were determined in home‐grown and imported wheat sampled at UK flour mills during the period February 1987 to December 1988. A total of 764 samples was analysed but not all the wheats were tested for all the residues; 140 of 474 samples examined for organophosphorus insecticides contained residues at levels above the reporting limit, 23 of 119 samples contained residues of gamma‐HCH, seven of 104 contained carbon tetrachloride and one of 104 contained 1,2‐dibromoethane. No residues of urea, carbamate or anilide herbicides, carbendazim, carbaryl or methyl bromide were detected in 32, 40, 44 and 45 samples respectively. Inorganic bromide levels in 45 samples examined were consistent with natural occurrence. Only a single imported wheat was found to contain a residue (of 1,2‐dibromoethane) at a level in excess of UK statutory maximum residue levels.
Vectors of plant pathogens and opportunities for the control of the diseases they transmit
Authors: Plumb Roger T.
Published: November 2006

Many plant pathogens, viruses, fungi and bacteria, are spread by intermediaries or vectors. For some this is their only method of spread and for most viruses vectors are the normal agents of dispersal. Fungi, bacteria and some viruses are carried passively, as contaminants of the vector, whereas most viruses have a complex biological interaction with their vectors which is only now beginning to be understood.

The control of pathogens carried passively can be achieved only by preventing contact between vector and pathogen. Therefore options for control include killing either vector or pathogen by a toxic pesticide or deterring the feeding of a potential vector. Viruses infecting plants cannot be killed by chemicals, therefore control has to be directed at the vector. The biological interactions between vector and virus offer opportunities for interfering with the transmission processes without recourse to toxic material.

Interactions, especially between viruses and their vectors, are discussed in relation to current and future opportunities for control.
Baculoviruses as vectors for foreign gene expression in insect cells
Authors: Atkinson Allan E. , Weitzman Matthew D. , Obosi Louis , Beadle David J. , King Linda A.
Published: November 2006

Recombinant DNA technology has enabled the expression of a large number of eukaryotic genes in vitro. There has been growing interest in recent years in the development of baculovirus expression vectors as an easily manipulated gene expression system. Both virus and insect cell culture are relatively easy to handle, and biologically active proteins have been produced abundantly from a variety of eukaryotic, prokaryotic and viral genes. This review describes the molecular biology of baculoviruses and some of the current applications of the baculovirus expression system in insect cells. Specific emphasis is placed on those features relevant to the use of this system in pesticide research.
Microdroplet application for determination of comparative topical and residual efficacy of formulated permethrin to two populations of diamond back moth (plutella xylostella L.)
Authors: Hall Franklin R. , Adams Andrew J.
Published: November 2006

An on‐demand, uniform droplet generator was used to apply 120 μm diameter drops of formulated permethrin either directly onto 3rd‐instar Plutella xylostella, of two Ohio populations, or onto the abaxial surface of leaf discs (1‐1000 drops cm−2) to which those larvae were subsequently exposed. Incorporating a fluorescent tracer (Saturn Yellow GT‐17N) in the spray mixture confirmed that „direct hit”︁ larvae had received a topical dose from a single droplet. There was little difference in the LC50/LD50 for either population of P. xylostella when 24 and 48 h mortality assessments from direct hits were compared, but the LD50 of Celeryville larvae was 6‐8 times greater than that of Fremont larvae. Residual deposits of 120 μm drops containing approximately the LC50, based on the topical assays, revealed that a droplet density providing a dose per cm2 leaf surface of more than 1000 times the LD50 was required to cause median mortality. The efficiency of utilisation, based on the topical LD95 values, was 0.0006% and 0.072% for Fremont and Celeryville larvae, respectively.
Non‐destructive method for estimating methyl bromide residues in apples during aeration following fumigation
Authors: Sell Charles R. , Moffitt Harold R.
Published: November 2006

A method is presented for estimating the persistence and concentration of residual free methyl bromide (MB) present in apples during the aeration period following fumigation. The method is based on determining the rate of decline in concentration of methyl bromide in the exhaust air stream during aeration. The rate was shown to follow two consecutive pseudo‐first‐order decay curves. The first component of the curve resulted primarily from removal of MB from the free air space in the chamber, and the second component resulted from the desorption of MB from the apples. Estimates of the concentration of MB residue in apples were obtained from the regression parameters for the second decay curve. The technique gave good estimates of the residue concentration over a wide range of fumigation conditions and ventilation rates, and may be useful for determining the duration of aeration period required to achieve a proposed residue tolerance of 0.2 mg kg −1 methyl bromide.
The degradation of diflubenzuron and its chief metabolites in soils. Part III. Fate of 2,6‐difluorobenzoic acid
Authors: Nimmo Wijnand B. , Joustra Kees D. , Willems Antonius G. M.
Published: November 2006

2,6‐Difluorobenzoic acid, one of the two primary diflubenzuron metabolites, is rapidly and completely degraded in soil. Times to 50% disappearance were 9 and 12 days in two agricultural soils. [14C]Carbon dioxide was an ultimate product of the ring‐14C‐labelled compound. A part of the radioactivity, increasing with time to one third of the applied dose of 1 mg kg−1, could not be extracted from the soil.
The toxicity of phosphine, methyl bromide, 1,1,1‐trichloroethane and carbon dioxide alone and as mixtures to the pupae of red flour beetle, Tribolium castaneum herbst
Authors: Rajendran Somiahnadar
Published: November 2006

The toxicity of phosphine, methyl bromide, 1,1,1‐trichloroethane (methyl chloroform) and carbon dioxide and mixtures of phosphine + methyl bromide, methyl bromide + methyl chloroform, phosphine + carbon dioxide, and methyl bromide + carbon dioxide to one‐ to two‐day‐old pupae of Tribolium castaneum Herbst was studied. Joint action ratios estimated at LD50 and LD90 for a 24‐h exposure indicated no enhancement of toxicity for mixtures of phosphine and methyl bromide, or methyl chloroform and methyl bromide on the pupae. Carbon dioxide up to 40% in air enhanced the toxic action of phosphine as well as of methyl bromide. Higher levels of carbon dioxide, however, failed to improve the toxicity of phosphine or methyl bromide proportionately. Carbon dioxide used alone produced a maximum of 11% mortality of the pupae exposed to 10–70% levels for 24 h. The order of toxicity of the fumigants both at LD50 and LD90 was phosphine > methyl bromide > methyl chloroform.
Measurement of simazine residues in chickpeas, Cicer arietinum, by gas–liquid chromatography
Authors: Allender W. J.
Published: November 2006

A method is described for the measurement of simazine [2‐chloro‐4,6‐bis(ethylamino)‐1,3,5‐triazine] residues in chickpeas (Cicer arietinum). Ground chickpea samples were extracted with dichloromethane, followed by clean‐up on alumina. Gas‐liquid chromatography using metribuzin [4‐amino‐ 6‐tert‐butyl‐4,5‐dihydro‐3‐methylthio‐1,2,4‐triazin‐5‐one] as internal standard with thermionic detection was used to quantify simazine residues. The limit of detection was 0.02 mg kg−1 and the recoveries of simazine from chickpea samples (0.1–4 mg kg‐1) averaged 92%.
Herbicide penetration across isolated and intact leaf cuticles
Authors: Baker Edward A. , Chamel Andre R.
Published: November 2006

Penetration of four herbicides (atrazine, diclofop‐methyl, dinoseb and glyphosate‐mono(isopropylammonium) salt) was followed through isolated pear leaf cuticles into agar and across intact cuticles of Argenteum (ARG) mutant pea leaves from monosized droplets (300 μ diam.) during 48 h following application. Penetration into pea leaves ranged from low for glyphosatemono(isopropylammonium) (5% of amount applied) and atrazine (14%) to rapid for dinoseb (91%) and diclofop‐methyl (82%). A major proportion (90%) of the dinoseb retained in the tissues underlying the site of droplet application migrated across the cuticle and the epidermal layer of cells. In contrast, only a small proportion (13%) of the dinoseb entering the leaf was transported to the tissues surrounding the treatment zone. Corresponding values for diclofop‐methyl were 61% and 4% respectively. Initially, dinoseb also penetrated rapidly through isolated pear leaf cuticles, 36% of the applied dose being recovered in an agar receiver disc 4 h after treatment, but subsequent uptake was slower. Penetration of glyphosate‐mono(isopropylammonium) also decreased after 4 h whereas atrazine and diclofop‐methyl diffused steadily through isolated cuticles up to 216 h after treatment. The incorporation of ‘Tween 20’ or ‘Agral 90’ (1 g litre−1) into the formulation reduced the penetration of glyphosate‐mono(isopropylammonium) through isolated pear leaf cuticles.
Uptake and metabolism as mechanisms of selective herbicidal activity of the 1,2,4‐triazolo[1,5‐a] pyrimidines
Authors: Hodges Craig C. , De Boer Gerrit J. , Avalos Javier
Published: November 2006

In order to identify the factors providing the triazolopyrimidines with a wide range of selectivity amongst agriculturally important plant species, studies were made on the uptake and metabolism of a representative compound, N‐(2,6‐dichlorophenyl)‐5,7‐dimethyl‐1,2,4‐triazolo[1,5‐a]pyrimidine‐ 2‐sulfonamide. This compound is much more phytotoxic to dicots than to monocots. Experiments showed that variations in leaf morphologies and geometries relative to spray applications resulted in different herbicide dosages applied to plant species used in selectivity evaluations. However, this parameter did not have a statistically significant correlation to herbicide selectivity measurements. Characterization of the metabolic pathways showed that the major herbicide metabolites involved methyl hydroxylation or hydroxylation of the aniline ring followed by glucose conjugation. Since these metabolites were not exclusive to either monocots or dicots, herbicide selectivity does not appear dependent on the pathway of metabolism. Studies on the kinetics of metabolism suggest instead that metabolic rate was important. Monocots metabolized the herbicide rapidly and generally were tolerant while the opposite was true of dicots.
Use of gas chromatographic retention indices for quantitative structure activity relationship studies of dialkyl phenyl phosphates
Authors: Gandhe Balkrishna R. , Purnanand  , Prasad Rameshwar , Danikhel Rajinder K. , Shinde Shankarrao K. , Srivastava Rajendra K. , Batra Balwant S. , Rao Karumuru M.
Published: November 2006

Thirty‐five dialkyl phenyl phosphates analogous to methyl and ethyl paraoxon were synthesized and their insecticidal activity against house fly (Musca nebulo) determined. Gas chromatographic retention indices (GCRI) at 200°C for all the phosphates were determined on OV‐101, DB‐1701 and DB‐WX fused‐silica capillary columns. The retention indices on polar and nonpolar columns (DB‐1701 and OV‐101, DB‐WX and OV‐101) considered together were shown to be related to the Hansch hydrophobic constant (II). Multiple regression analysis using the least‐square method was carried out to establish the linear relationships between insecticidal activity and GCRI along with the Hammett constant, (σ).

The multiple correlation coefficients (r) of various parameters obtained using GCRI were found to be as significant as those obtained using II values. It was found that both hydrophobic and electronic effects made a significant contribution to the insecticidal activity of dialkyl phenyl phosphates. It is concluded that GCRI on two columns can be used directly as an indicator for hydrophobicity in QSAR studies provided that a suitable pair of polar and nonpolar columns is used for this purpose.
Recent development in suspoemulsions
Authors: Mulqueen Patrick J. , Paterson Eric S. , Smith Geoffrey W.
Published: November 2006

Suspension emulsions or suspoemulsions result from the combination of an emulsion phase, containing one or more active ingredients, with a continuous phase also containing active ingredients but in the form of a solid dispersion. Advantages of such products, which can contain as many as four complementary biologically active ingredients, are elimination of tank mixing; a reduced inventory of products; reduction in the number of applications to a given crop; and savings in time and money. The development of suspoemulsions is discussed and a novel, easy method for their preparation, using latexes, is described. Such products are also useful as feedstock emulsions for other suspension emulsions as well as constituting a stable oil‐in‐water emulsion delivery system in their own right.
Phloem mobility of xenobiotics. IV. Modelling of pesticide movement in plants
Authors: Grayson B. Terence , Kleier Daniel A.
Published: November 2006

A model is described that accounts for the effect of physical properties on the mobility of a xenobiotic within the phloem tissue of a plant. This model builds on the intermediate permeability hypothesis by incorporating the effect of acid dissociation. The relative importance of lipophilicity and acid‐base properties of compounds is discussed. The sensitivity of the model predictions to plant parameters such as the nature of the sieve tube membranes is also explored. Experimental support for the model is presented using examples from the literature. The systematic behaviour of mobility as a function of physical properties for both non‐ionized and acidic compounds is well accounted for by the model with only rare exceptions. Application of the model to commercial plant‐protection chemicals is generally consistent with experimental observations. Thus, many of the herbicides that are known to be phloem‐mobile are predicted to be so by the model. However, none of the selected fungicides and only a few of the insecticides are predicted to be phloem‐systemic, again in general agreement with observation.
Fate of carbendazim in rice tissues after seed or foliage treatments
Authors: Parida Tarulata , Nayak Mandakini , Sridhar R.
Published: November 2006

Carbendazim was quantified employing reversed‐phase high‐performance liquid chromatography in rice coleoptiles, radicles and shoot portions of seedlings of different ages grown from seeds treated with the fungicide, and in shoot portions of adult plants at different times after foliar treatment with the fungicide. The highest levels of carbendazim were detected in the coleoptiles four days after germination of seeds and the radicals contained the lowest concentrations. Carbendazim residues declined with time in the shoot portions of seedlings and of adult plants. However, the levels of carbendazim detected in the shoot tissues of 21‐day‐old seedlings grown from treated seeds [recommended dose of 10 mg a.i. 10g−1 seeds] and in adult plants 35 days after treatment (recommended dose of 0.25 g a.i. litre−1 spray fluid) correspond to the reported lasting ability of the fungicide in terms of protection against blast of rice.
An electrophysiological study of susceptible (cooper) and resistant (kdr; super‐kdr) strains of the adult housefly (Musca domestica L.) using an isolated mesothoracic leg preparation
Authors: Gibson Amanda J. , Osborne Michael P. , Ross Hamish F. , Sawicki Roman M.
Published: November 2006

Sensory fibres in the isolated metathoracic leg of houseflies were used as a neurophysiological assay to investigate nerve insensitivity factors in knockdown‐resistant strains (kdr, super‐kdr) against DDT, the pyrethroids deltamethrin and RU15525, and the N‐alkyl amide BTG502. Several neurophysiological effects were induced by these compounds, but the only consistent one was an elevation of the spontaneously occurring firing rate. Whilst both resistant strains possess a nerve insensitivity factor, that of the more resistant super‐kdr flies appeared to be weaker than that of kdr. When probed with BTG502, super‐kdr nerves were no more resistant to this compound than those of the susceptible Cooper strain. Kdr nerves were considerably less sensitive (at least 100‐fold) than either of these other two strains. These results indicate that the voltage‐dependent sodium channels are different in all three strains and that the higher resistance shown by super‐kdr over kdr flies cannot be accounted for by simple enhancement of the kdr nerve‐insensitivity factor. Therefore, target sites other than the voltage‐dependent sodium channel have to be considered to account, fully for super‐kdr resistance. Such sites could occur at synaptic contacts, possibly involving phosphorylation of proteins and/or calcium‐ion regulation.
An investigation of the non‐solvent‐extractable residues of [14C]chlorpyrifos‐methyl in stored wheat
Authors: Matthews Wendy A.
Published: November 2006

The residues of [14C] chlorpyrifos‐methyl remaining in wheat after solvent extraction accounted for 28% of the applied dose after an extended period of storage. A bioassay of these residues was carried out using Tribolium castaneum and a significant reduction in the numbers of adults reaching maturity was observed. Attempts to release the non‐solvent‐extractable residues using an enzymic digestion procedure were unsuccessful, as were several of the chemical solubilisation procedures investigated. A water/methanol extraction system was successful in releasing up to 86% of the radioactivity leaving 10% still non‐extractable. Analysis of this solubilised residue revealed that 59% was present as the pyridinol metabolite of chlorpyrifos‐methyl and 26% was a polar material composed of two main components. Bioassay tests of these metabolites revealed that the reduction in the number of insects reaching maturity could be associated with the pyridinol metabolite.
Photolysis of flucythrinate
Authors: Chattopadhyaya S. , Dureja P.
Published: November 2006

Photolysis of flucythrinate ((RS)‐α‐cyano‐3‐phenoxybenzyl (S)‐2‐(4‐difluoromethoxyphenyl)‐3‐methylbutyrate) in solution (methanol) by UV light (> 290 nm) and as a thin film on glass by exposure to sunlight yields products resulting from ester cleavage. The major product in solution is formed via photo‐induced decarboxylation. When thin films are exposed to sunlight, flucythrinate has a half life of 8 days on glass and 3 days on a leaf surface.
Sensitivity analysis of a mathematical model for pesticide leaching to groundwater
Authors: Boesten J. J. T. I.
Published: November 2006

The sensitivity of pesticide leaching to pesticide/soil properties and to meteorological conditions was assessed by calculations with an existing convection—dispersion model. The model assumes equilibrium sorption (Freundlich equation), first‐order transformation kinetics and passive plant uptake. The extent of pesticide leaching was characterized by the percentage of the dose leached below 1 m depth. The calculations were carried out for a humic sand soil cropped with maize and exposed to Dutch weather conditions.

In general, the percentage leached was found to be very sensitive to the sorption coefficient, the Freundlich exponent (describing the curvature of the isotherm) and the transformation rate. The percentage leached was moderately sensitive to weather conditions (wet/dry years), long‐term sorption equilibration and the relationship between transformation rate and temperature. Sensitivity to the extent of plant uptake was only significant for pesticides with low sorption coefficients. Sensitivity to soil hydraulic properties was small. The effect of application in autumn instead of in spring was found to be very large for non‐sorbing pesticides with short half‐lives. The sensitivity to spatial variability in sorption coefficient and transformation rate was found to be substantial at low percentages leached.
Pharmacological properties of presynaptic muscarinic receptors in the sixth abdominal ganglion of the cockroach, Periplaneta americana L.
Authors: Le Corronc Hervé , Hue Bernard
Published: November 2006

The effects of muscarinic agonists on acetylcholine (ACh) release in the cercal‐afferent giant‐interneuron synapses of the cockroach have been studied using the single‐fibre oil‐gap method. Decrease in amplitude of the cEPSP was induced by pressure ejection of arecoline (ARE), carbachol (CCh) and oxotremorine free base (OXO) within the sixth abdominal (A6) ganglion. This depressive effect was dose‐dependent without any effect at the post‐synaptic site in the range of concentrations used. The concentration for 50% of cEPSP inhibition of the most commonly used muscarinic agonists was determined. The rank order of potencies was: ARE > CCh > OXO > McN‐A‐343 > bethanechol (BET). Plateau levels of 56%, 54% and 68% were reached when increasing the concentration of ARE, CCh and OXO respectively. McN‐A‐343 and BET had an inhibitory effect on ACh release but higher doses also acted at the postsynaptic level. Furthermore, muscarinic agonists were able to evoke uIPSP and a smaller inhibitory effect of ARE and OXO was observed in presence of picrotoxin.

It is concluded that the ACh release in the cockroach A6 ganglion is modulated by presynaptic muscarinic receptors which are possible target sites for insecticides. The presence of putative muscarinic receptors on inhibitory GABAergic interneurons, involved in pre‐ and postsynaptic inhibition is suspected.
Cross‐resistance between acylurea insect growth regulators in a strain of Plutella xylostella L. (Lepidoptera: Yponomeutidae) from Malaysia
Authors: Ismail Fauziah , Wright Denis J.
Published: November 2006

The activities of the acylurea insect growth regulators, chlorfluazuron, teflubenzuron and difubenzuron, and the neurotoxic macrocyclic lactone, abamectin were assessed against a laboratory susceptible (FS) strain and a field (Cameron Highlands, Malaysia (CH)) strain of the diamondback moth, Plutella xylostella L. using a leaf‐dip bioassay at 20°C. The time taken to achieve end‐point mortality was found to vary considerably (9–17 days), being fastest with abamectin against the FS strain and slowest with difubenzuron against the CH strain. The order of activity (LC50 at F6/7) against second‐instar larvae of both strains was: abamectin > chlorfluazuron = teflubenzuron ⋙ difubenzuron. Subsequent assays (F14) with the acylureas, flufenoxuron and hexaflumuron against the FS strain suggested that the former was slightly more active than chlorfluazuron or teflubenzuron, the latter slightly less active. The CH population was found to be 12.6‐, 6.7‐, 6.4‐ and 2.3‐fold less sensitive to difubenzuron, teflubenzuron, chlorfluazuron and abamectin respectively than the FS strain. Selection of sub‐populations of the CH strain with chlorfluazuron (CHL‐SEL) and teflubenzuron (TEF‐SEL) for six generations (F6‐11), resulted in LC50 resistance ratios of 109‐ and 315‐fold respectively when compared with the FS strain, equivalent to an 18‐ and a 46‐fold increase in resistance compared with the unselected CH strain. Marked cross‐resistance was also demonstrated between chlorfluazuron and teflubenzuron in both sub‐populations. However, there was no evidence of cross‐resistance to dijlubenzuron and abamectin and little or no cross‐resistance to flufenoxuron and hexaflumuron. Resistance to chlorfluazuron and teflubenzuron appeared to be relatively unstable in the TEF‐SEL compared with the CHL‐SEL sub‐population (over 6–9 generations). However, reselection of the TEF‐SEL population with chlorfluazuron (F18–20) led to a very rapid increase in resistance to chlorfluazuron and particularly teflubenzuron. For the latter compound, resistance factors of about 1000000 were obtained (F19, 21). Such values are probably only semi‐quantitative, as above a certain level of resistance feeding bioassays with acylureas (compounds which are active to a significant extent by ingestion) are likely to become rate‐limiting.
Isolation of microsomal cytochrome‐p450 isozymes from Ustilago maydis and their interaction with sterol demethylation inhibitors
Authors: Kapteyn Johan C. , Pillmoor John B. , De Waard Maarten A.
Published: November 2006

A procedure for the isolation of microsomes containing cytochrome‐P450 isozymes from Ustilago maydis is described. Yields of P450 amount to approximately 19(±+ 6) pmol mg−1 of microsomal protein. The wavelength of maximum absorbance of the reduced carbon monoxide difference spectrum is 448‐449 nm. The azole fungicides prochloraz, etaconazole, imazalil, triadimefon and 3‐(2,4‐dichlorophenyl)‐2‐(1H‐1,2,4‐triazol‐1‐yl)‐4(3H)‐quinazoline, which differ markedly in toxicity to U. maydis, all induce type II binding difference spectra at extremely low concentrations (10−9‐10−8 M). The DMI concentrations which cause half saturation of type II binding difference spectra (IC50) do not correlate with the fungicidal activities of the azoles. Binding of carbon monoxide to ferrous cytochrome‐P450 was only slightly inhibited to different degrees by the DMIs tested. However, the inhibition of carbon monoxide binding also does not correlate with fungitoxicity of the DMIs. The results in this paper suggest that the spectrophotometric studies with this preparation are not useful for evaluating selective toxicity of DMIs to intact sporidia of U. maydis.
Surfactant‐enhanced foliar uptake of some organic compounds: Interactions with two model polyoxyethylene aliphatic alcohols
Authors: Stock David , Edgerton Bernadette M. , Gaskin Robyn E. , Holloway Peter J.
Published: November 2006

Interactions occurring during the surfactant‐enhanced foliar uptake of seven model organic compounds were examined using two homogeneous surfactants, hexaethylene glycol monotridecyl ether (C13E6) and hexadecaethylene glycol monododecyl ether (C12E16). Surfactant–compound and compound–surfactant interactions were detected by measurement of their relative uptake rates following application of c. 0·2 μl droplets of the corresponding radiolabelled formulations. The magnitude of surfactant–compound interaction was found to vary according to the physicochemical properties of both the compound and the surfactant, and was influenced by surfactant concentration and target plant species. Interactive and non‐interactive mechanisms, both leading to substantial enhancement of compound uptake, could be identified, but their precise nature could not be elucidated. Although penetration of C13E6 into the site of application appeared to be essential in order to activate the uptake of a compound, substantial absorption of C12E16 was not always required to produce the same effect. The results are discussed in the light of possible sites and modes of action for activator polyoxyethylene surfactant adjuvants.
Determination of mobilities of organic compounds in plant cuticles and correlation with molar volumes
Authors: Bauer Hubert , Schönherr Jörg
Published: November 2006

Mobilities of selected pesticides in plant cuticles have been measured using unilateral desorption from the outer surface (UDOS). The outer layer of the cuticle limits the rate of foliar uptake and solute mobilities in this layer have been determined. The primary parameter measured was the first‐order rate constant of desorption. From these rate constants, permeances, half‐times of penetration and diffusion coefficients could be calculated. Rate constants were lowest in bitter‐orange (Citrus aurantium L.) leaf cuticles and this cuticle turned out to be very size‐selective, as rate constants decreased by a factor of 264 when molar volumes increased by only a factor of about three. Rate constants measured using green‐pepper (Capsicum annuum L. cv. Bell Boy) fruit cuticles were larger by one to two orders of magnitude and this cuticle was considerably less size‐selective. A good correlation between rate constants and molar volumes was observed for cuticles from both plant species, which means that rate constants can be estimated from molar volumes of pesticides. Rate constants of desorption are mobility parameters which do not depend on lipophilicity of solutes. Thus, it is now possible to separate the contributions of mobilities and solubilities in cuticles to rates of foliar uptake of pesticides.
Leaching of atrazine and hexazinone from Abies nordmanniana (Steven) spach plantations
Authors: Felding Gitte
Published: November 2006

The content of the herbicides atrazine and hexazinone was measured in drainage water from seven to ten‐year‐old plantations grown with Abies nordmanniana (Steven) Spach on two clayey soils in Denmark. The concentrations of atrazine varied between 0.06 and 7.79 μg litre−1. The concentrations of hexazinone were different at the two locations, ranging from 0.07 to 2.09 μg litre−1 at Bremersvold and from 3.47 to 42.66 μg litre−1 at Koege. Metabolites of both herbicides were identified.
Effects of nonionic surfactants on cuticular sorption and penetration of 2, 4‐dichlorophenoxy acetic acid
Authors: Tan Siyuan , Crabtree Garvin D.
Published: November 2006

Surfactants increase the uptake of some foliar‐applied chemicals to a greater extent than would be expected from their effects on surface tension and spray coverage. This study of the uptake of 2, 4‐D [(2, 4‐dichlorophenoxy)acetic acid] evaluated the effect of surfactants on penetration through and sorption by isolated cuticles of apple leaves. [14C]2, 4‐D was placed in glass chambers affixed to enzymatically isolated adaxial apple leaf cuticles after the cuticle segments had been treated with various surfactants. The same surfactant pretreatments were included in sorption studies in which cuticle segments were immersed in [14C]2, 4‐D for 96 h. Quantities of 2, 4‐D passing through or sorbed by the cuticle were determined. Similar experiments were conducted with unaltered cuticles and cuticles dewaxed with chloroform. The hydrophile‐lipophile balance (HLB) of polyethylene‐glycol‐based surfactants was inversely related to the sorption of those surfactants by the cuticles and penetration of 2, 4‐D. Sorption of 2, 4‐D by apple leaf cuticles was unaffected by surfactant pretreatment. Dewaxed cuticle membranes showed a similar response to 2, 4‐D penetration and sorption following the surfactant pretreatment.
Oil formulation of pyrethroids for contamination of tsetse flies (Glossina spp.) through tarsal contact with treated targets
Authors: Langley Peter A. , Perschke Helmut , Hussain Manzoor
Published: November 2006

Mosquito netting side panels of targets used for tsetse control were treated with lambda‐cyhalothrin, either dissolved in a mixture of acetone and a chlorohydrocarbon oil, ‘Cereclor’® > (ICI, UK) or as a conventional wettable powder formulation suspended in water. Treated netting samples were weathered under natural conditions in full sun in Zimbabwe. Following brief tarsal contact of test insects (adults of Glossina morsitans morsitans Westw.) with treated netting, the wettable powder induced 100% knockdown for four months after treatment but 24‐hour mortality levels were reduced from the third month onwards. The oil formulation induced 100% knockdown for up to ten months following treatment and 100% mortality at 24 hours for up to eight months. Chemical assay showed that after two months there had been a rapid reduction in the amount of active ingredient to only 20% of that applied using the wettable powder, whereas the oil formulation took seven months to fall to this level. Provided that at least 5% of the original amount of pyrethroid remained on the fabric it was quite effective and the superiority of the oil formulation was further enhanced by the observation that the starting concentration was only 25% of that of the wettable powder.
Indol‐3‐ylacetic acid‐ and calmodulin‐regulated Ca2+‐ATPase: A target for the phytotoxic action of hexachlorocyclohexane
Authors: Sharada Khandavilli , Salimath Bharathi P. , Shetty H. Shekar , Gopalakrishna N. , Karanth K.
Published: November 2006

In rice seedlings, the organochlorine insecticide hexachlorocyclohexane (HCH) and its four major isomers—α,β, γ, and δ—have been shown to elicit their phytotoxic action by interacting with indol‐3‐ylacetic acid (IAA)‐regulated growth and Ca2+‐ATPase activity. When rice seedlings were grown in the presence of 0.34 mM HCH, seedling vigour was reduced to 33% of the control. A similar effect was observed when seedlings were grown in the presence of the γ and δ isomers, but not with the α and δ isomers of HCH. This reduced vigour could be restored by treating the seedlings with 100 nM IAA, suggesting that HCH and its isomers (γ and δ) limit either IAA synthesis or action or both. In a microsomal fraction from rice seedlings grown in the presence of either HCH or its isomers, the calmodulin‐regulated Ca2+‐ATPase activity was inhibited as follows: technical HCH = 46%, α isomer = 80%, β isomer = 72%, γ isomer = 65% and δ isomer = 62% of the control value, respectively. TLC analysis suggested that the various isomers of HCH are metabolised by the plant, except for the δ isotner, which accumulated. This isomer, along with the degraded products of other isomers, may be responsible for the phytotoxic action of HCH.