The volatilization rates of 14 pesticides from the surfaces of aqueous solution, soil, rice leaf and glass were measured in the laboratory, and the correlations with their physicochemical parameters were analyzed. On the volatilization from the surface of aqueous solution, the air/water partition coefficient by the head-space gas method, the volatilization rate by the purge & trap method and the relative volatility were measured. There was a good and positive correlation among the air/water partition coefficient, the volatilization rate and the relative volatility. There was a good and positive correlation between the volatilization rate and Henry constant (H). On the volatilization from soil, the air/soil partition coefficient was measured by the head-space gas method. There was a positive correlation between the coefficient and VP/(WS·K_oc) or H/K_oc (VP: vapor pressure, WS: water solubility, K_oc: soil adsorption constant). On the volatilization from the surface of rice leaf, the air/rice partition coefficient by the head-space gas method and the volatilization rate by the purge & trap method were measured. There was a positive correlation between the air/rice partition coefficient and the volatilization rate. There was also a positive correlation between the volatilization rate and the VP or the VP·MW (MW: molecular weight). In addition, on the volatilization from the surface of glass coated with pesticide, the volatilization rate was measured by the purge & trap method. There was a positive correlation between the volatilization rate and the VP. On the volatilizability from the surface of each compartment, the correlations between the volatility from the surface of aqueous solution and the H, the volatility from the soil surface and the H/K_oc, and the volatility from the leaf surface and the VP, VP·MW or VP/(WS·K_oc) were all high. It was concluded that these physicochemical parameters were the main factors in controlling the volatilizability from each compartment.

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A coryneform bacterium, strain A-1, produced extracellularly an aryl acylamidase, which was markedly activated by preincubation with a substrate, acetanilide (AAN). This specific enzyme was purified by ammonium sulfate fractionation under the coexistence of AAN, followed by chromatographic fractionations with DEAE-Sephadex A-50 and Sephadex G-100. The enzyme purified 263 fold over crude preparation gave a single band on SDS-PAGE. The molecular weight was estimated to be ca. 127, 000, which was appreciably larger than those of known bacterial aryl acylamidases. The activated enzyme tended to be more tolerant of high temperatures and some metal ions, compared with the nonactivated one. This purified and activated enzyme also hydrolyzed aniline-based pesticides such as naproanilide, chlorpropham, propanil and linuron. Kinetic analysis of substrate-saturation curves of these chemicals showed that the compound's overall ability to act as a substrate was higher for chemicals having unsubstituted aniline moiety than for ones having Cl-substituted aniline moiety in the molecule. It was strongly suggested that the enzyme conformation was induced to fit readily for unsubstituted acylanilides due to the activation with AAN.

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Translocation and metabolism of a fungicide, pefurazoate (pent-4-enyl N-furfuryl-N-imidazol-1-ylcarbonyl-DL-homoalaninate, Healthied^®), were investigated in rice seedlings after the seeds were treated with three different kinds of ¹⁴C-labeled pefurazoate. Three weeks after seeding in a sand culture medium, the radioactivity in the seeds accounted for 81.3-86.3%, and decreased to 54.1-55.8% during the following two-week culture. The decrease was mostly due to the translocation to the shoots and the roots. Pefurazoate was so readily metabolized that the parent molecule was reduced to 49.1-58.2% of the total radioactivity in the seedlings three weeks after seeding. During the following two-week culture it was further reduced to 22.6-25.4%, remaining mostly in the seeds (90.2-93.9%). Major metabolites were 4-pentenyl (RS)-2-furfurylaminobutanoate, (RS)-2-furfurylaminobutanoic acid, 1-((RS)-1-carboxylatopropyl)-3-hydroxypyridinium, N-(furan-2-ylcarbonyl)-glycine, (RS)-2-aminobutanoic acid, imidazole, hydantoin and hydantoic acid. Conjugated metabolites were observed in small amounts. The metabolic pathway of pefurazoate in the rice plants was almost similar to that in soil.

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Effects of long-term, repeated application of chlorothalonil on cellulose decomposition in soil and soil microflora were estimated in field experiments under upland conditions. Chlorothalonil was applied to a plot twice a year for six years at the rate of 2.25g a.i./m² (normal-dosage plot) and 11.25g a.i./m² (high-dosage plot). In the normal-dosage plot, cellulose decomposition was suppressed only in winter. Such a seasonal variation was also observed in the high-dosage plot with incomplete recovery in summer. High-dosage, long-term application increased the populations of total and gram-negative bacteria and decreased the population of actinomycetes in the soil. The populations of total and Cx-cellulase (1, 4-β-D-glucan 4-glucanohydrolase, EC 3.2.1.4) producing fungi remained unchanged, while the population of fungi which vigorously decomposed filter paper decreased as the application rate, fungal inoculum potential to decompose crystalline cellulose completely at 25°C decreased only in the high dosage plot. It was supposed that the suppression of cellulose decomposition in the high dosage plot was attributed to the difference in fungal flora in the soil rather than to the low fungal population level.

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Seven morphologically different yeast-like symbiotes were isolated from eggs of the rice brown planthopper, Nilaparvata lugens. To determine their taxonomic affiliation, molecular analysis of DNA encoding 18S-ribosomal RNA was carried out. PCR amplifications of their DNA preparations using the well conserved regions of Saccharomyces cerevisiae 18S-rDNA as primers produced a single main band of DNA having the predicted size of 1.3 and 1.6Kbp on electrophoresis. Digestion of these DNAs with restriction endonucleases gave different band patterns on electrophoresis, indicating that these seven yeast-like microorganisms belong to different taxonomic affiliations.

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Susceptibility of Earias insulana and Pectinophora gossypiella collected from cotton fields to fenvalerate and fenpropathrin was studied by a simple dipping method. This method is suitable for monitoring susceptibility of lepidopteran pests to pyrethroids. In 1985, the LC₅₀ of fenvalerate against the Multan colony of E. insulana was 1.5ppm and that against the Hyderabad colony was 1.8ppm. The LC₅₀ value of fenpropathrin against this species was 0.46ppm. Against P. gossypiella, LC₅₀ values of these two pyrethroids were almost equal: 10 to 13ppm respectively. The susceptibility of these species was monitored in Multan, Pakistan from 1985 to 1991. In 1990, fenvalerate was replaced by its active isomer, esfenvalerate. No difference in the susceptibility of each species to the pyrethroids was observed during this period.

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A number of N-(1, 1, 3-trimethylindan-4-yl)aryl- or heteroaryl-carboxamides were synthesized and their structure-activity relationships studied. A series of compounds showed potent fungicidal activity against grey mold caused by Botrytis cinerea, in addition to rice sheath blight caused by Rhizoctonia solani. Pyridine-3-carboxamides substituted by Cl, Br, CH₃ or CF₃ at 2-position exhibited high activity against both diseases. Monosubstituted pyrazine-3-carboxamides, furan-3-carboxamides, pyrazole-4-carboxamides and thiazole-5-carboxamides gave as high activity against both diseases in pot tests and SDC of Botrytis cinerea in an enzyme test as the 2-substituted pyridine-3-carboxamides. 2, 5-Dimethylfuran-3-carboxamide gave activity against both diseases and SDC as high as 2-methylfuran-3-carboxamide, whereas the activities of 2, 4-dimethyl and 2, 4, 5-trimethylfuran derivatives were extremely low against grey mold in a pot test. Pyrazole-4-carboxamides and thiazole-5-carboxamides showed the same substituent effects as the furan derivatives. Among the compounds of this series, 4-methylthiazole-5-carboxamide (BC340) and 2-chloropyridine-3-carboxamide (BC723) were most potent against both diseases.

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A strain (R) of German cockroach originally collected in Ginza, Tokyo, and selected with permethrin in our laboratory showed cross resistance to various pyrethroids and DDT, and moderate resistance to organophosphate and carbamate insecticides as compared to a susceptible (S) strain. In vitro studies on the degradation of ¹⁴C-fenvalerate by subcellular fractions suggested that the major activity was in the soluble fraction and the microsomes, but no significant difference was found in either of these fractions between the S and R strains. Little, if any, difference in the synergistic effect of metabolic inhibitors, DEF and PBO, on the fenvalerate toxicity to the R and S strains supported the conclusion that metabolism is not an important factor for the pyrethroid resistance in this strain. Although in the R strain the content of cytochrome P450 in the microsomes was 2.6-fold larger than in the S strain, it may be due to cytochrome P450 species which are not involved in fenvalerate degradation. Electrophysiological studies on the exposed abdominal nerve cord clearly demonstrated that the nerve system of the R strain was much less sensitive than that of the S strain to all the pyrethroids tested and DDT, indicating that the so-called KDR was a predominant factor for the pyrethroid resistance in this strain.

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Alkenyl side chains in the alcohol moiety of natural pyrethroids and (S)-bioallethrin are easily oxidized by mixed function oxidases (mfo) and chemical oxidants, but the products have not been defined in detail. Thus, the absolute configuration of the 7-hydroxy derivative of (S)-bioallethrin, a major metabolite by mouse and rat liver microsomes, was examined by a modified Mosher's method which compared the ¹H NMR spectra of the esters with both enantiomers of α-methoxy-α-(trifiuoromethyl)phenylacetic acid, and the (7R)-configuration was assigned for it indicating that the mfo attacked a (pro-R)-hydrogen at the 7-position of the pyrethroid. Further, oxidized products of the alcohol moieties by SeO₂ and m-chloro-peroxybenzoic acid (MCPBA) were analyzed by NMR and GC-MS after their purification by HPLC. Both the regioselectivity of these reagents and their relative reactivity on the four different alkenyl side chains were similar to those of mammalian and insect mfo. This result indicated that SeO₂, and MCPBA oxidation could be used as a model reaction for metabolic studies of pyrethroids.

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A toxicokinetic model was proposed to describe the in vivo dynamics of ¹⁴C-fenvalerate applied topically to a susceptible (S) and a pyrethroid resistant (R) strains of the German cockroach. Values of various kinetic parameters, such as cuticular penetration (k₁), rub-off (k₂), degradation (k₃), binding (k₄) and excretion (k₅), were estimated by computer simulation. The result showed that the penetration and rub-off rates were slower in the R strain than in the S strain. No significant difference was found in degradation, binding and excretion rates between the strains. The R strain also showed behavioral resistance to the “flushing out” effect of fenvalerate. Coupled with the results in the previous paper, it is concluded that the control failure of the R strain by pyrethroids was brought about by a combination of three factors, behavioral avoidance, decrease in cuticular penetration and insensitivity at the site of action.

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[in Japanese]

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The behavior and fate by runoff of pesticides applied to paddy field were investigated. The necessary sample numbers for measurement of pesticide concentration in river water were allow to less when pesticides were applied at all over of river basin. But, many samples were necessary for the pesticides applied by aerial application to the limited area. In the rainy times, the runoff amount of pesticides per unit time was influenced by the variation of flow water volume rather then the variation of pesticide concentration. On the research of the change of pesticides concentration in main river of Chiba prefecture, pesticides in river water are not presumed to be influenced on human health. For six years from 1983 to 1988, runoff and leaching of 21 pesticides were measured with lysimeters. The runoff percentages and the water solubility were significantly related statistically (r=0.872, n=18). Furthermore, the runoff percentages of pesticides from lysimeters and those from actual paddy fields to river water also related significantly (r=0.870, n=8). With the analysis of the multiple regression equation, it was found that the factors as water solubilities of pesticides, application method, application time, formulation, rainfall were related with pesticide runoff from the paddy field and behavior and fate of pesticides in the aquatic environment was predictable.

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In the course of study on new pyrethroids, it was found that organosilicon compounds substituted with silicon atom at the quaternary carbon atom of ethofenprox were showed pyrethroidal insectactivity. Among them dimethyl (4-ethoxyphenyl) silylmethyl-3-phenoxybenzyl ether (SSI-116) was selected as the most potent candidate, which has broad-spectrum insectactivity, extremely low fish toxicity and low mammalian toxicity. The comparison between SSI-116 and ethofenprox in various biological activity to insects suggested that SSI-116 acted as a bioisostere of ethofenprox against insects and was classified to type I pyrethroids. But in fish toxicity the large difference between them was observed, that is the LC₅₀ value for carp of SSI-116 and ethofenprox were >562ppm and 5.0ppm, respectively. In the field trials SSI-116 was effective agent for control of pests in rice paddy field. The results suggested that sila-substitution of known pesticides might be available method for future pesticide development.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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