The effects of cartap hydrochloride (Padan^®, cartap·HCl) on soil enzyme activities, respiration and nitrification were examined for 30 or 60 days in laboratory-conditioned upland and flooded soils. Cellulase and saccharase activities were not influenced even by 1, 000ppm cartap·HCl treatment in either condition. Phosphatase activity in 1, 000ppm treatment decreased but then recovered. Protease activity under flooded conditions was depressed by 1, 000ppm treatment during the first 15 days, but became even higher than in the untreated soil after 30 days. This activity under upland conditions decreased in the 100 and 1, 000ppm treatments over the entire 60 day period. Oxygen uptake was retarded by 1, 000ppm treatment during 30 days, but it subsequently recovered. In the soils treated with cartap·HCC at 100 and 1, 000ppm, NH₄⁺-N accumulated but NO₂^--N and NO₃^--N diminished. These findings suggested that nitrifying organisms were affected by high concentrations of cartap·HCl. All of the four enzyme activities, respiration and nitrification showed very little or no change at a normal application rate (10ppm) of the chemical in the soil under upland and flooded conditions.

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Bacillus thuringiensis formulation, Bacilex^®, was applied to apple and cabbage leaves to assess the fate of viable spores. The number of viable spores on leaves exposed to sunlight decreased rapidly with the lapse of time after application, but persisted on leaves for a long time under shade or with the interception of sunlight. A decrease in the number of viable spores and in the pathogenicity to the silkworm were distinctly observed with the exposure to light having a maximum spectral energy distribution of 450-500μm, moderate at 500-600μm, and slight at 650-700μm. Temperature and rainfall after application scarcely affected the number of viable spores.

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In a continuing study on the alteration of the experimental insecticide carbosulfan (2, 3-dihydro-2, 2-dimethylbenzofuran-7-yl N-dibutylaminothio-N-methylcarbamate) in acidic media, the effect of four different acids was investigated. [Carbonyl-¹⁴C] Carbosulfan dissolved in acetonitrile containing 10% acetic, formic, n-butyric or 1N hydrochloric acid was converted into carbofuran, biscarbofuran-N, N′-disulfide, a mixture of polysulfide analogs of carbosulfan (CFS_nNBu₂, n=2-n), and a mixture of biscarbofuran-N, N′-polysulfides as common alteration products. The rate of carbosulfan breakdown to these products appeared to be related to the strength of the acid. The acid-catalyzed breakdown of two of the major alteration products of carbosulfan, i. e, CFS₂NBu₂ and CFS₃NBu₂, were also studied. Both CFS₂NBu₂ and CFS₃NBu₂ were substantially more stable in the presence of acetic acid than carbosulfan, although the same types of alteration products were obtained. The rates of breakdown of CFS₂NBu₂ and CFS₃NBu₂ were first-order in substrate.

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Mepronil remaining after 80 days exposure to sunlight on the silica gel chromatoplate was 34.1 and 62.2% depending on the season (Sept. to Dec. and Nov. to Jan., respectively). The half-life is estimated as 36 days during Sept. to Dec. which was shortened to half when a photosensitizer, xanthone, was mixed with it. The degradation in water when irradiated with ultraviolet light was only 32.0% after 80hr at 30°C. Twelve photoproducts were identified as 3′-(1-hydroxymethylethoxy)-2-methylbenzanilide; 3′-isopropoxy-2-hydroxy-methylbenzanilide; 3′-isopropoxy-4′-hydroxy-2-methylbenzanilide; 3′-hydroxy-2-methylbenzanilide; 1-hydroxy-3-oxo-2-(3′-isopropoxyphenyl) isoindoline; 3′-(1-carboxyethoxy)-2-methylbenzanilide; 3′, 4′-dihydroxy-2-methylbenzanilide; 2-methylbenzamide; 2-methylbenzoic acid; 2-hydroxymethylbenzoic acid; phthalide; and 2-carboxybenzaldehyde. The results indicate that initially hydroxylation of mepronil occurs on the four positions, followed by further oxidation, hydrolysis, cyclization or cleavage.

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Two new techniques to evaluate repellency against the German cockroach (Blattella germanica L.) were devised, a test tube method and a beaker method. The former estimates the repellent impact on a roach attracted by roach excrement on a paper filter. The latter, estimating effectiveness by changes in the number of roaches in a beaker, is an excellent method for evaluating olfactory repellency. Among the reference compounds, α-naphthoquinone, 2-hydroxyethyl-n-octylsulfide and naphthalene were effective in the test tube method, however their 2% sublimates were not effective in the beaker method. Those compounds were thus not judged as promising olfactory repellents. The oils of Japanese mint (Mentha arvensis) and spearment (native and Scotch type, Mentha specata) were the most effective among 92 such substances. Strong mosquito repellents such as oils of citronella, lavender, rosemary, and penny royal had little or no effect against the cockroach.

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Five compounds with the olfactric repellency for German cockroach (Blattella germanica L.) and smoky brown cockroach (Periplaneta fuliginosa S.) were isolated from oils of Japanese mint (Mentha arvensis subsp. L. haplocalyx Briquet var. piperascens Holmes) and Scotch spearmint (Mentha spicata Hunds var. tenuis (Michx) Briq.). The compounds were identified as (-)-limonene, (-)-menthone, (-)-menthol, (-)-carvone and (+)-pulegone by retention time of GC, specific rotatory power, and IR, NMR and mass spectra. The activity of the (+)-enantiomers and racemic compounds was very low. Some correlations between repellency and functional groups of C₁-methyl group, C₄-isopropyl group, C₄-isopropenyl group and C₁-C₂ or C₁-C₆ double bond were suggested.

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The adsorption-desorption patterns of piperophos by paddy field soils and adsorbents were studied using a slurry method in relation to properties of soil colloids. The adsorption isotherms of piperophos fitted empirical Freundlich isotherms. Large k values were obtained with montmorillonite, humic acids and soils containing montmorillonite or highly organic matter, while small ones were found with kaolinite and soils with low organic matter content. k values were not correlated with clay and organic matter contents. 1/n values for organic matter rich soils and humic acids were less than 1, but those for clay minerals, montmorillonitic soils or soils of low organic matter content were greater than 1. The desorption isotherms of piperophos with water showed a hysteresis. The herbicide was desorbed easily from kaolinite and organic matter poor soils, but with difficulty from montmorillonite, humic acids, montmorillonitic soils and organic matter rich soils. Strong binding of piperophos to montmorillonite and soil organic matter was assumed.

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Non-fungitoxic concentrations of tricyclazole, pyroquilon, 4, 5, 6, 7-tetrachlorophthalide, PCBA (2, 3, 4, 5, 6-pentachlorobenzyl alcohol), coumarin, pp-389 (4, 5-dihydro-4-methyltetrazolo [1, 5-a] quinazolin-5-one), s-triazolo[4, 3-a] quinoline and N-methyl-2-quinolone inhibit melanin biosynthesis in Pyricularia oryzae. These compounds do not inhibit growth of P. oryzae in culture or conidial germination and appressorial formation on isolated Bryophyllum pinnatum epidermal strips, but block melanization of the appressoria and prevent penetration of the epidermal wall. The epidermal wall is penetrated by infection hyphae from 80 to 95 percent of control appressoria. Successful penetration is observed only when appressoria are melanized. All compounds prevent conversion of scytalone to melanin but not the conversion of vermelone to melanin by P. oryzae. This investigation indicates that these compounds act on the pathogen by a similar or an identical mechanism to protect plants by interfering with appressorial functions required for epidermal penetration.

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Acephate, O, S-dimethyl acethylphosphoramidothioate, was applied to a tobacco leaf and its fate, incorporation and translocation in the leaf were studied. The compound decreased rapidly for 3-7 days after treatment and the concentration reached 1ppm about 2 months later. In the leaves, acephate was metabolized to methamidophos, which was almost entirely accumulated after 7 days. The degradation of acephate applied on a glass plate was less than on a leaf surface. Acephate deposited on a leaf surface was incorporated into the leaf tissue with 22% of the residue after 24 hour and 82% after 7 days. Acephate applied on the left half surface of a leaf moved to the midrib for 2 days and then moved to the right half of the leaf as a metabolite, methamidophos. During the translocation, the concentration of methamidophos in the midrib was low. The translocation of acephate from the bottom half surface of a leaf to the upper portion was quicker than that of horizontal shift. It was also observed that the acephate translocated poorly from one leaf to another.

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Acephate (O, S-dimethyl acethylphosphoramidothioate) granules were applied to the soil surface of a growing tobacco pot. Its fate, translocation and distribution in the leaf and plant were studied. The compound was taken up from the soil to the leaves through the root, and the concentration in the leaves reached its highest level on the 10th day after treatment, decreasing to 1-3ppm after 50 days. Acephate concentration in leaves of plants grown in soil to which 4g of the insecticide had been applied was higher than in those grown in soil with a 2g application, but the compound disappeared within the same period of time in the two cases. The residue in the soil disappeared even more rapidly than in the plant. Acephate in leaves was distributed more around the edge than in the center and the concentration found in leaves of the lower stalk was higher than that farther up the stem.

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The bioconcentration of dialkyl 1, 3-dithiolan-2-ylidenemalonates in fish, Oryzias latipes L., varied from 0.68 for the dimethyl analog to 102 for the di-n-butyl analog, depending on the hydrophobicity, log P, of the compounds. Accumulation was complete within 2 days at 18°C. Following this, all the concentrations in both fish and water declined with time. The rate of decrease in the aquarium system seemed to be governed by bioconcentration at the site of metabolism in fish and by susceptibility to metabolizing enzymes. The half-life of the compounds in aqueous KOH (0.1N) increased progressively from 3min for the dimethyl analog to 60min for the di-t-butyl analog, relating well to alcoholic α-substitution or the resulting electronic effect expressed as σ*. A similar tendency was observed on the compound decrease in the aquarium.

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When 2, 4-dichloro-¹⁴C-phenyl 3′-methoxy-4′-nitrophenyl ether (chlomethoxynil, the active ingredient of X-52^®) was orally administered to rats, the radiocarbon was rapidly and almost completely excreted into feces and urine (78 and 17%, respectively) within 96 hours. Radiocarbon level in the blood reached the maximum between 8 and 12hr after administration, but none of the tissues examined had a high residual radioactivity after 96hr. From the urine, two conjugated metabolites (2, 4-dichlorophenyl sulfate and β-D-glucuronide) were obtained, accounting for 12 and 1.2% of the dose. 2, 4-Dichlorophenyl 4′-amino-3′-hydroxy-phenyl ether (1.2%) and six minor metabolites (0.03-0.2%), which were probably produced through 3′-demethylation, 4′-nitro reduction, 6-hydroxylation and/or conjugation, were also characterized. In the feces, 62% of the applied ¹⁴C-chlomethoxynil was found to remain unchanged. Such metabolites as 2, 4-dichlorophenyl 4′-amino-3′-methoxyphenyl ether (2% of dose), 2, 4-dichlorophenyl 4′-amino-3′-hydroxyphenyl ether (3%) and 2, 4-dichlorophenyl β-D-glucuronide were identified.

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[in Japanese]

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[in Japanese]

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Pesticide applications often cause phytotoxicity on various crops under particular conditions. Examples of phytotoxic symptoms on agricultural crops in the field were surveyed and compiled, and mechanisms of this phytotoxicity studied. Phytotoxicity in vegetables grown on compost prepared from rice straw previously applied with organochiorine fungicide in the field was found to be caused by pentachlorobenzoic acid and 2, 3, 5, 6-tetrachlorobenzoic acid derived from the fungicide. Cucumber plant showed a leaf burn from vapor drift of a herbicide applied near paddy fields. The results of biological assays on cucumber seedlings applied with a vapor of various herbicides in a plastic tunnel coincided well with the cases in the field. Furthermore, chemical analysis indicated that evaporation of some kind of herbicide was greatly enhanced from aqueous solutions than from soils. Leaf burn on a rice plant given short interval applications of a herbicide, propanil, and carbamate-insecticides was due to the inhibition of the propanil hydrolyzing enzyme in the plant by carbamates. Organophosphorus insecticides easily cause phytotoxicity, especially against Chinese cabbage. The phytotoxic symptoms by 22 organophosphorus insecticides on this vegetable are classified as leaf necrosis, chlorosis, and abnormal leaf-vein. Chlorophyll, carotene and carbohydrate content decreased and total nitrogen content increased in Chinese cabbage leaves with leaf burn. Peroxidase and acid phosphatase activities also increased. These changes were similar to that of senescence or infection with fungal or viral pathogens. In the leaves with chlorosis, chlorophyll and carbohydrate content decreased. In those leaves bleached by the application of phosalone, the carotene apparently decreased as early as 2 hours after application without visible symptoms. The defect of carotene caused the photolysis of chlorophyll. Organophosphorus insecticides, which caused chlorosis on Chinese cabbage leaves, inhibited the Hill reaction at 10^-4-10^-6M. Furthermore, these organophosphates, strong inhibitors of the Hill reaction, were found to be hydrophobic. These compounds may have a high affinity to chloroplast, inhibit the electron transport in the chloroplast, and cause decomposition of chlorophylls.

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Metabolic experiments of lindane and related compounds are reviewed. Lindane and other BHC isomers produced 2, 4, 6-trichlorophenol as the major oxidative metabolite by rat liver microsomes. A mechanism was shown to be direct oxygenation of the cyclohexane ring followed by dehydrochlorinations. Microsomes from rat liver and housefly abdomen effectively metabolized lindane to (36/45)- and (346/5)-pentachlorocyclohexene and (36/45)-hexachlorocyclohexene in addition to 2, 4, 6-trichlorophenol. A reaction mechanism was proposed which includes electrophilic attack by an activated oxygen to chlorine or hydrogen. Microsomes metabolized isomers of tetra-, penta-, and hexachlorocyclohexene to tetrachlorocyclohexenol isomers, 2, 4, 5-trichlorophenol and 2, 3, 4, 6-tetrachlorophenol, respectively. The (346/5)-isomer of pentachlorocyclohexene also gave an abundant amount of pentachlorocyclohexenol isomer. These oxidative reactions were shown to proceed mainly via ene-like hydroxylation accompanied by double bond migration. Reductive dechlorination of lindane and related polychlorocyclohexenes under anaerobic condition was found using microsomes and NADPH. 1, 2, 4-Trichlorobenzene was produced abundantly from (36/45)-hexachlorocyclohexene in this condition. Correlations of this biochemical reductive dechlorination with electrochemical reduction were illustrated. 4-Chloro-, 2, 4-dichloro-, 3, 4-dichloro-, 2, 3, 5-trichloro- and 2, 4, 5-trichlorophenylmercapturic acids were identified as the main mercapturic acid metabolites of lindane. Their formation from (346/5)-tetra-, (346/5)-penta-, (36/45)-penta-, and (36/45)-hexachlorocyclohexene was proposed based on in vitro experiments using rat liver soluble fraction and glutathione. A mechanism was proposed which includes substitution by glutathione of allylic chlorine with or without double bond migration. All these findings elucidated the in vivo metabolic pathways of lindane degradation in the rat and in the housefly.

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There are 1, 200 crop diseases caused by pathogenic fungi in Japan. Control of these diseases is of vital importance to a sufficient and stable supply of foodstuff. The development of safe agricultural chemicals free of mammalian toxicity and environmental pollution are urgently needed. The authors believe the protection against processes of infection to be one of the most important factors in combatting fungal diseases. The processes of rain-borne and air-borne fungal infections were investigated with reference to various growth stages in their life cycles after they were noted on the surface of a host plant. We isolated antifungal substances, including citrinol and one of the phytoalexins, and their chemical structures were determined. Furthermore, studies were made on the response of host plants to stimulations by causal fungi. On the basis of information obtained, especially on the nature of the relationships between host plants and parasites, the successful development of two fungicides, soybean lecithin and sodium bicarbonate, was made. The former has a preventive effect against vegetable powdery mildews, and the latter has a curative effect against vegetable, rose, apple and pear powdery mildews in particular. Because of the non-mammalian-toxicity of both soybean lecithin and sodium bicarbonate, they are expected to be useful for application during crop harvest.

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