摘要:

AbstractThe mechanisms responsible for>6000‐fold permethrin resistance in a pyrethroid‐selected strain of house fly, Learn‐PyR, were investigated. Through electrophysiological,in vitrometabolism,in vivopenetration and synergism studies it was demonstrated that the resistance mechanisms consisted of enhanced metabolic detoxification via the mixed‐function oxidase (MFO) system, target‐site insensitivity and decreased cuticular penetration. The major resistance mechanism was the MFO‐mediated detoxification. The elevated MFO activity was correlated with higher levels of cytochrome P‐450, cytochrome b5and NADPH‐cytochrome c reductase activity. The kinetics of the latter showed similarKmbut greaterVmaxvalues in the Learn‐PyR than in the susceptible strain, suggesting that the elevated activity was due to an altered amount, but not an altered form, of the enzyme. The Learn‐PyR strain showed widely varying levels of resistance to the pyrethroids tested. Comparison of the pyrethroid structures with the resistance ratios revealed that resistance was highest in the presence of an unsubstituted phenoxybenzyl alcohol moiety. Substitution or certain modifications of the alcohol moiety reduced the level of resistance. Structure of the acid moiety or the presence or absence of ana‐CN group did not affect the resistance level. These results are discussed with reference to the resistan

ISSN:0031-613X    

DOI:10.1002/ps.2780170302

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe rate of gas interchange between the atmosphere within a freight container and the external air has an important influence on the effectiveness of in‐container fumigation. When a container is exposed to the wind or is in motion, the rate of gas interchange may be much greater than that under static conditions. The effect of motion or wind on gas interchange was studied by observing gas loss from freight containers, both empty and loaded with rice, while stationary and while being transported by rail. The gas interchange rate was determined by measuring the rate of loss from the containers of either a combination of a fumigant, methyl bromide, and a relatively inert tracer gas, carbon monoxide, or of carbon monoxide alone. In loaded containers the difference between the loss rate constants of methyl bromide and carbon monoxide (0.29.0.03d−1) was within the range expected for the reaction of methyl bromide with rice. After allowing for gas loss caused by changes in temperature and pressure, the component of the interchange rate constant attributable to air motion was found to be proportional to gas‐tightness as measured by a steady‐state pressure test, and also to the relative air speed over the container. Under conditions of varying wind and train speed, the fraction of the initial concentration of gas remaining was found to be an exponential function of wind run past the container. When wind effects were not important, it was found to be an exponential function of distance tr

ISSN:0031-613X    

DOI:10.1002/ps.2780170303

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA mathematical model describing gas loss from freight containers is presented. The general model incorporates terms relating to the influence on gas loss of sorption, wind, transport velocity, terrain traversed, temperature variation and barometric pressure changes and provides a mathematical description of the variation of average gas concentration within a container. This expression can be integrated giving a function predicting the concentration–time product achievable under particular environmental conditions. For methyl bromide fumigation of containers loaded with grain in transit in the open, the model predicts, as found experimentally, that the variation of concentration with time is a function of distance travelled after allowance for losses from sorption. The general model is of a form that, with minor modification, can be applied to any enclosure to predict the time course of a fumigation for specified environmental conditions and load. Examples are given of its use to calculate the typical and extreme loss rates expected from particular phenomena, to evaluate how transport conditions and loss rates affect the effectiveness of methyl bromide fumigation in a freight container, and also the time required for the fumigant concentration to fall to a safe leve

ISSN:0031-613X    

DOI:10.1002/ps.2780170304

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractAmerican sycamore (Platanus occidentalsL.) seedlings grown in a hydroponics system were treated with a growth regulator, maleic hydrazide (MH) or sodium chloride, or a combination of the two. Application of maleic hydrazide or sodium chloride retarded plant growth, but combined application did not show significant interaction effects. Treatment with both sodium chloride and MH reduced the dry weight of plant tissue to a greater extent than sodium chloride application alone. Elemental analyses of various plant parts revealed that MH was generally without effect on the level of either sodium or chloride ions. In old stem tissue, however, treatment with MH had no effect in the absence of sodium chloride but was associated with lower chloride content in its presence.

ISSN:0031-613X    

DOI:10.1002/ps.2780170305

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe kinetics of the degradation in soil of propyzamide and nine analogues have been measured at two temperatures (28 and 60°C). The degradation rates of propyzamide were determined in sterilised soil and in soil perfusates. The results obtained are in agreement with a chemical degradation of propyzamide and its analogues. Relationships were established between degradation rate constants and physicochemical parameters of the compounds: log k = −aσ+bπ +cwhere σ = Hammett constant, π = hydrophobic constant,a,b,care con

ISSN:0031-613X    

DOI:10.1002/ps.2780170306

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effects of synthetic pyrethroids on the feeding behaviour of the two‐spotted spider miteTetranychus urticae(Koch) were studied using a modified leaf disc technique. Four different concentrations of the pyrethroids fenvalerate and permethrin and of the organophosphorous insecticide phosmet were sprayed on to Henderson lima bean plants in the laboratory. A water spray was used as a control. Leaf discs were taken from each treatment, including the control, at 2h, 1, 2, 4, 7, 11 and 14 days after treatment. One mite was placed on each disc, allowed to acclimatise and then observed for 1 h. Experiments were conducted under laboratory light at 25 (±1.5)°C and 30 (±2)% r.h. Mites on untreated and phosmet‐treated discs spent an average 70–95% of the time feeding; mite behaviour appeared to be unaffected by phosmet. In contrast, mites often spent only 5–40% of the time feeding on discs treated with fenvalerate or with the higher rates of permethrin. In response to pyrethroid residues mites exhibited hyperactivity, longer search periods and reduced feeding, reduced oviposition and a preference for areas with lower residues. These changes in mite behaviour may partially explain mite outbreaks in the field on apple trees following treatment with p

ISSN:0031-613X    

DOI:10.1002/ps.2780170307

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effects of systemic fungicides on the host‐pathogen interface between barley and powdery mildew were studied using cytological methods and specific staining procedures. Propiconazole, etaconazole, bitertanol, triforine, imazalil, nuarimol, tridemorph and fenpropimorph, which are all inhibitors of sterol biosynthesis, stopped growth of the fungus 2 days after application and led to deposits of plant origin around haustoria; these contained polysaccharides, especially callose. This encapsulation resembled the reaction often observed in resistant plants. In contrast, pyrazophos and ethirimol, applied at reduced concentrations, inhibited the fungus at the haustorial stage but did not induce encapsulation. These results suggest that encapsulation is not simply a reaction to the previously damaged fungus, but may be an indirect effect of sterol biosynthesis‐inhibiting fungicides on the host metabolism which is elicited by the fungus. The results are discussed in the context of previous observations on the modes of action of these fungici

ISSN:0031-613X    

DOI:10.1002/ps.2780170308

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe development, testing and application of computer models for the behaviour of organic chemicals, especially pesticides, in soil and ground water has been reviewed. Detailed data are needed on the structure and properties of the soil and ground‐water systems, and on the flow of water through these systems. Adsorption and transformation of organic chemicals can be studied in the laboratory and the results introduced into the models. The mathematical techniques most frequently used for the solution of the differential equations are briefly discussed. Some models for the behaviour of pesticides in the root zone have been tested against results of field trials and some interesting deviations between computations and measurements emerged. Techniques for the simulation of the behaviour of organic chemicals in the ground‐water zone are also available. However input data for the models are often lacking, as are also results of field studies for testing the mod

ISSN:0031-613X    

DOI:10.1002/ps.2780170309

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractBioaccumulation, describing selective transfer of a chemical from compartments into organisms, and biomagnification, describing such a transfer from organisms of lower trophic levels to organisms of higher trophic levels in food chains, are environmental partitioning processes that have received special attention because of their potential toxicological significance. Both phenomena are determined by certain physicochemical properties of a given chemical and by the environmental systems concerned, as well as by the chemical and metabolic degradability of the chemical in these systems. A number of correlations between the physicochemical properties and the bioaccumulation potential of a chemical have been established of which the relationship between then‐octanol/water partition coefficient and the bioaccumulation factor is the most relevant. The predictive value and the limitations of these correlations have been discussed. Included in this discussion is the question as to what extent degradability allows the predicted bioaccumulation potential of a chemical to come into effect in different species. A pragmatic use of the established relationships and bioaccumulation test results in a stepwise approach is recommended to provide a realistic estimate of the bioaccumulation potential of a chemical for the assessment of its environmental ris

ISSN:0031-613X    

DOI:10.1002/ps.2780170310

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractComparison of the most recent EPA and OECD guidelines shows that there are small but significant differences in the protocols recommended for determining the rates of hydrolysis of industrial chemicals for environmental hazard assessment. The detailed conditions given in these guidelines, such as purity and concentration of active ingredient, co‐solvent, pH, buffer type and concentration, temperature, sampling times, and methods of analysis, have been examined in relation to their effects on the accuracy of the measured rates of hydrolysis. It is suggested that the two protocols could be made more similar while still obtaining results that will be sufficiently accurate for estimations of abiotic environmental persistenc

ISSN:0031-613X    

DOI:10.1002/ps.2780170311

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY