The plate theory requires only a theoretical plate number and an effective adsorption ratio as factors for the predication. The latter is defined as the ratio calculated according to the concept that the amount of chemical in a stationary solution is regarded as an adsorbed one, assuming the concentration is the same as that of mobile solution. The adsorption formula, bulk density of soil, saturated water content, dispersion coefficient, and rate of flow are necessary factors for the rate theory. The plate number, effective adsorption ratio, and dispersion coefficient can be extracted from an experimental leaching curve. This is obtained by a simple system in which a 14.9ppm picric acid solution is dropped on a 3.3cm long soil column at a constant rate of flow. Previously two extracted factors were substituted into the polynomial for the plate model and produced a simulating curve after computation. The extracted dispersion coefficient produced another simulating curve by means of substitution into the differential equation for the continuous model. Both simulating curves were approximately the same as the experimental one. The above three factors significantly varied with the rate of water flow. The coefficients of variation (%) of the theoretical plate numbers and the dispersion coefficients in regard to regression lines between the rate of water flow were as large as 35 and 28, respectively, while that of the effective adsorption ratios was as small as 1.5. This shows that there are some difficulties in reproducing soil columns accurately. A significant correlation as high as 0.851 as the square of the correlation coefficient was observed between the theoretical plate number and the Brenner number, (rate of flow)×(column length)/(dispersion coefficient). The movement of a chemical at various pore water velocities can be exactly simulated whenever the dispersion coefficients are exactly estimated.

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Four herbicides, chlornitrofen (CNP), benthiocarb, molinate, and simetryne, were applied to lysimeters containing a mineral alluvial soil or a humic volcanic ash soil, and the concentrations of these herbicides in the leached water and the top 20cm soil-layer were successively determined for three years (1978-1980). (Molinate was determined only in 1980.) The vertical distribution in soil layers was also determined at the end of experiment. These herbicides, except molinate, were applied to soils which were watered at two leaching rates (20 and 50mm a day) with and without incorporation of wheat or rice straw in the soil (“plow back” and “not plow back”). The amounts of these four herbicides moving to a lower soil layer and leached out increased with the increase in water solubility of the herbicide as follows: molinate>simetryne>benthiocarb>chlornitrofen. In general, the herbicides were eluted out in the highest amounts and at the earliest time in the first year when the soils were packed in lysimeters, probably because of the loose consistency. In the first year also, the leached amounts of herbicides were always larger in the alluvial soil than in the volcanic ash soil. In the second year, however, the reverse was true for some herbicides; this may be because the soil consistency was higher and the leaching rate of water was lower in the alluvial soil. This was supported by the fact that the eluted amounts of herbicides increased with the increase in leaching rate.

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The behavior of bifenox, a diphenyl ether herbicide, methyl 5-(2, 4-dichlorophenoxy)-2-nitrobenzoate, in soil was studied using two types of ¹⁴C-bifenox labeled at the nitrophenyl and dichlorophenyl rings, respectively. The evolution of ¹⁴CO₂ occurred in a passable amount in non-flooded (upland moisture condition) soil, but scarcely in flooded soil. Organic volatile metabolites were hardly detected under either moisture condition. In the early stage of degradation, fair amounts of the degradation products were adsorbed by soil with noncovalent bonds. Degradation patterns obtained under various degradation conditions, such as sterilization before or after pre-incubation, long term pre-incubation, addition of glucose, and different concentration of the chemical, indicate that the hydrolysis of the ester bond is due mainly to microbial reaction and the reduction of the nitro group to amino group is mainly to chemical (non-biological) reaction.

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Topical toxicity of malathion and fenitrothion to susceptible, malathion resistant and fenitrothion resistant brown planthoppers, Nilaparvata lugens STÅL, was determined. LD₅₀ values of malathion to susceptible, malathion resistant and fenitrothion resistant strains were 4.42, 1, 590 and 71.8, and LD₅₀ values of fenitrothion to those strains were 7.79, 71.4 and 336μg/g, respectively. An in vitro degradation study of ¹⁴C-methyl malathion by 900g supernatants showed that malathion resistant and fenitrothion resistant strains degraded ¹⁴C-methyl malathion more than susceptible ones and the most of the degradation products were carboxylesterase products. Most of the ¹⁴C-methyl malathion degradation activity was found in the 105, 000g supernatant fraction. β-Naphthyl acetate hydrolyzing enzymes of the brown planthopper were separated by thin layer agar gel electrophoresis. The aliesterase activity of malathion resistant and fenitrothion resistant strains was significantly higher than that of susceptible one. ¹⁴C-Methyl malathion degradation activity was observed only around aliesterase bands which showed a high aliesterase activity.

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An efficient method for the liberation of CNP-amino (4-aminophenyl 2, 4, 6-trichlorophenyl ether) and nitrofen-amino (4-aminophenyl 2, 4-dichlorophenyl ether) from soil bound residues was studied. A soil sample was obtained from a paddy field treated with CNP-granules (4-nitrophenyl 2, 4, 6-trichlorophenyl ether) more than nine months earlier. In the acetone extract of the soil, 3.64ppm of CNP, 0.50ppm of CNP-amino, and 0.01ppm of nitrofen-amino were detected. However, large quantities of these amines (11.40ppm and 0.88ppm, respectively, at maximum) were observed in extracts from soils treated under strongly alkaline or acidic conditions. Fractionation of soil organic matter pre-extracted with acetone revealed that the amino compounds were largely associated with the humin fraction of the soil. A maximum amount of CNP-amino from soil bound residue was obtained by heating the acetone-extracted soil with 5N potassium hydroxide and sodium sulfide for 20hr at 100°C.

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The acute oral toxicity (LD₅₀) of equi-toxic doses of malathion plus a Carbamate insecticide was determined in mice and rats. The observed LD₅₀ of a “mixture” was compared with the expected LD₅₀ calculated from each LD₅₀ and LD₅₀ (expected)/LD₅₀ (observed) was used as a ratio of combined effect. Of 5 combinations studied in male mice, malathion plus BPMC was the only combination which exhibited a striking synergism (the ratio, 5.4). On the other hand, clear synergism was not observed with the combination of malathion plus one of the other carbamate insecticides, MTMC, NAC, XMC or MPMC. When malathion or BPMC was administered alone, the toxicity in female mice or male rats was not different significantly from that in male mice. In female mice, the synergism of malathion plus BPMC was similar to that in male mice (the ratio, 5.2). However, relatively less potent synergism was noted with the combination in male rats (the ratio, 2.0). The marked synergism of malathion plus BPMC could not be explained on the basis of an inhibition of the acetylcholinesterase (AChE) by malaoxon plus BPMC, or an inhibition of malathion's detoxication by BPMC.

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Investigations were made on whether or not freshwater fishes in the Sagami River were contaminated by the herbicides CNP (chloronitrofen), chlomethoxynil, molinate and benthiocarb (thiobencarb). Application of these herbicides to paddy fields is restricted during the rice planting season, so this investigation was carried out in July and the contamination levels of other months were compared. CNP was detected in all four species of fishes (pale chub, pike gudgeon, carp and crucian carp), and benthiocarb was detected in two species in July, 1980. The residual levels of CNP were from 0.055ppm to 0.61ppm, and those of benthiocarb were 0.02ppm and 0.10ppm. These values were similar to those found in pale chub, ayu, crucian carp and large mouth bass in July, 1981 tests; the residual levels of CNP were from 0.046ppm to 0.88ppm and those of benthiocarb from 0.04ppm to 0.11ppm, respectively. But in September, 1981, the residual levels were below a detectable level or detected only in very low concentrations. The bioconcentration ratio (concentration level in fish/concentration level in water) of CNP was supposed to be 420-8, 000 and that of benthiocarb 20-100, when estimated from the results of this investigation. But it was thought that the residual period in fish did not continued too long. Chlomethoxynil and molinate were not detected in any fish examined.

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Absorption and translocation of dialkyl 1, 3-dithiolan-2-ylidenemalonates by rice plants were determined by applying their aqueous solution to the root system or to the root and lower stem. Rice plants seemed to translocate the compounds through the transpiration stream via the root system and through the capillary system on the stem. The latter translocation was related to the hydrophobicity of the compounds, as was the former but inversely. Adsorption by soil did not affect the availability of the compounds to the plants except the most hydrophobic compound. Charcoal addition (0.17%w/w) to the soil reduced all the compound concentrations in water and their resulting availability to the plants was also reduced.

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Inhibition of Hill reaction by organophosphorus insecticides was examined to clarify their mechanism of phytotoxic action on Chinese cabbage leaves. Among organophosphates tested, those which caused no phytotoxic symptom did not affect Hill reaction at concentrations below 10^-4M. Degree of inhibition of Hill reaction varied dependent on the organophosphates in the case of those causing necrotic symptoms on Chinese cabbage leaves. Dimethoate did not affect Hill reaction, while fenthion and fenitrothion inhibited reaction by 50% at a concentration of 10^-5M. Organophosphates causing chlorotic symptoms were strong inhibitors and suppressed the reaction at 10^-5-10^-6M. All the inhibitors were hydrophobic. Even in the case of a series of compounds belonging to straight-chain alcohols, fatty acids, and polychlorobenzenes, the increase in their molecular weight and concomitant decrease in water solubility apparently were in parallel with their ability to increase inhibitory activity. Thus, hydrophobic compounds are considered to be inhibitory for Hill reaction. These compounds may have high affinity to chloroplasts resulting in inhibition of the electron transport in them and causing decomposition of chlorophyll.

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Variations in neurophysiological activity of a number of DDT-type compounds against the excised central nerve cord of the American cockroach were quantitatively analyzed using steric, hydrophobic and electronic parameters of both aromatic and benzylic substituents. The steric effect of aromatic substituents in terms of van der Waals volume was found to play the most significant role in determining variations in activity of DDT, DDD and prolan analogs having various aromatic p, p′-substituents. For methoxychlor analogs having various benzylic substituents, van der Waals volume, the STERIMOL length parameter, L, and the hydrophobicity of substituents were found to determine variations in activity. The insecticidal activity of these classes of compounds measured by injection into the abdomen of the American cockroach, from which the oxidative metabolic factor was eliminated as far as possible by injection of piperonyl butoxide, correlated very well with neuroexcitatory activity when the transport factor was separated using the hydrophobicity parameter.

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Fungicide sensitivity of the field isolates of Pyricularia oryzae, the rice blast fungus, was studied in vitro and in vivo. Isoprothiolane (diisopropyl 1, 3-dithiolan-2-ylidenemalonate) and IBP (S-benzyl diisopropyl phosphorothiolate) were used as test fungicides. When mycelial sensitivities to the fungicides were examined by agar-medium dilution method, the sensitivity of an isolate was expressed by a linear line, y=a log x+b, where y is probit of mycelial growth inhibition rate and x is concentration (μg/ml) of the fungicide in the medium. A set of values of a and b in the equation, representing fungicide sensitivity of an isolate, was marked as a dot by plotting a against b. From the analysis of values of a and b for 2, 243 isolates from Japanese paddy fields, it was revealed that all of them were recognized as one group with high sensitivity to isoprothiolane whose regression line was a=4.687-0.717b. As for IBP sensitivity, they were grouped into two clusters, one was sensitive and the other was less sensitive; regression lines were a=6.167-1.046b and a=4.364-0.764b, respectively. Of 2, 243 field isolates, 57% were included in the latter group. This grouping coincided well with the result of disease control experiments. Values of minimum inhibitory concentration (MIC) of fungicides against mycelial growth did not always correlate with the in vivo sensitivity. The results also showed a wide range of distribution in fungicide sensitivity even among the sensitive group.

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Isouron is degraded to 3-[5-(1, 1-dimethyl-2-hydroxyethyl)-3-isoxazolyl]-1, 1-dimethylurea, 3-(5-tert-butyl-3-isoxazolyl)-1-methylurea (1) and 3-[5-(1, 1-dimethyl-2-hydroxyethyl)-3-isoxazolyl]-1-methylurea (8) in liquid culture of Rhizoctonia solani. The fungus also rapidly degraded isouron-related compounds, such as (1), 3-(5-tert-butyl-3-isoxazolyl)-1-hydroxymethyl-urea (2), 3-(5-tert-butyl-isoxazolyl)urea (3), 5-tert-butyl-3-aminoisoxazole (4) and 3-(5-tert-butyl-3-isoxazolyl)-1-methyl-1-formylurea (6), by oxidative hydroxylation of the tent-butyl group at the isoxazole ring and demethylation of the urea side chain. The metabolites formed from (1) were (2), (3) and (8). (2) was degraded to (3) by deformylation of the urea side chain. (3) and (4) were converted into 3-[5-(1, 1-dimethyl-2-hydroxyethyl)-3-isoxazolyl] urea (9) and 5-(1, 1-dimethyl-2-hydroxyethyl)-3-aminoisoxazole, respectively, by hydroxylation of the tert-butyl group at the isoxazole ring. The metabolites from (6) were (1), (2), (3), (8), and (9). The pathway of the metabolic conversion of isouron by Rhizoctonia solani was proposed. Of the isolated metabolites, the herbicidal activity of (1) was nearly equal to that of isouron, but the others showed no activity against broad-leaf and grass weeds.

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Seven synthetic pyrethroids, phenothrin, cyphenothrin, permethrin, cypermethrin, S-5439, fenvalerate and fenpropathrin were found to be less toxic by injection than by topical application treatments to the armyworm P. separata (W). In comparison with lindane and fenitrothion, however, they were still several times more toxic. The greater topical toxicities of the pyrethroids are attributed to fast cuticular penetration. Cyanide containing compounds were generally slightly less toxic than their non CN containing analogues. The natural pyrethrins had about the same toxicities in injection as in topical application.

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[in Japanese]

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Quantitative analyses of aldrin and dieldrin were carried out by mass chromatography. The m/z 66 and 79 fragment ions of aldrin and dieldrin and the m/z 81 ion of the heptachlor epoxide as internal standard were selected for the measurements. The method is free from sample related interferences. Recoveries of aldrin and dieldrin which had been added to the soil were approximately 90%, and the limit of detection was 5ng for these compounds. The mass chromatographic method was applied for field soil samples.

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The structure-activity relationships of insecticidal 3-substituted-α-cyanobenzyl 3-(2, 2-dichlorovinyl)-2, 2-dimethylcyclopropanecarboxylates have been analyzed by the Hansch method against housefly, Musca domestica. The variation of the activity was shown to be mainly related to the variation of the hydrophobicity of the 3-substituent. The activity of the compounds whose 3-substituent has either π electrons or a lone pair at the β-position was about 2 times higher than the other compounds.

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Metabolic experiments of fenitrothion with mouse liver homogenate and mice were conducted, in order to examine whether an enantiotopic demethylation reaction occurs or not during the metabolism. Metabolic desmethylfenitrothion extracted was chemically derivatized into the diastereomeric phosphoramidothioate with (S)-(-)-α-phenylethylamine, which was analyzed by HPLC to determine their diastereomeric composition. The results showed that a larger amount of (R)_p-(+)-desmethylfenitrothion was produced with a lesser amount of a (S)_p-(-) enantiomer in both in vitro and in vivo metabolism, whose absolute stereochemistry was determined by comparative analysis of ¹H-NMR spectra of the diastereomers.

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[in Japanese]

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