Degradation of the herbicide MCPB-ethyl [ethyl 4-(4-chloro-2-methylphenoxy) butylate] in soils under flooded and upland conditions was investigated by means of GC equipped with an electron capture detector in the laboratory. MCPB-ethyl was degraded rapidly in soil under flooded and upland conditions, and MCPB [4-(4-chloro-2-methylphenoxy) butyric acid] was formed correspondingly. MCPB was also converted slowly to MCPA [(4-chloro-2-methylphenoxy) acetic acid] by β-oxidation of the side chain. In sterilized soil, MCPB-ethyl was moderately stable under both soil conditions. More than 72% of the MCPB-ethyl applied was recovered 28 days after treatment. These results suggest that the degradation process of MCPB-ethyl including hydrolysis of the ester is caused mainly by microorganisms in the soil. Half-life of the total amounts of MCPB-ethyl, MCPB and MCPA was 2-7 days under flooded soil conditions and 3-4 days under upland conditions.

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Susceptibility of carp, Cyprinus carpio, to 8 pesticides was evaluated at various stages in their life cycle from eyed eggs to fingerlings about 5cm in length. No remarkable change in susceptibility with growth was observed to trichlorfon, fenitrothion, phenthoate, diazinon and IBP (O, O-diisopropyl S-benzyl phosphorothiolate), which are organophosphorus insecticides or a fungicide, or to pentachlorophenol-sodium herbicide, showing that the chorion of the egg was not an effective barrier to permeation of these pesticides. However, susceptibility to chlornitrofen herbicide and endosulfan insecticide was low at the eyed egg stage, increased during the early growth stages and decreased with further growth. Data from the present study and others suggests that age-susceptibility patterns produced in carp can be grouped on the basis of chemical structure or mechanism for toxicological action of pesticides as in the case of the mallard duck, Anas platyhrynchos.

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The photodecomposition of prothiofos (O-2, 4-dichlorophenyl O-ethyl S-propyl phosphorodithioate) under ultraviolet (UV) light and sunlight was studied. In aqueous and hexane solutions, prothiofos exposed to UV light was rapidly decomposed. Decomposition proceeded mainly from dechlorination at the 2-position of the phenyl group, oxidative desulfuration of the P=S moiety, cleavage of P-O-aryl and P-S-alkyl linkages and the subsequent liberation of phenols. More than 12 photodecomposed products from prothiofos were detected by gas-liquid chromatography (glc); 10 of these were identified. In hexane solution, prothiofos formed a phospholane compound upon UV-irradiation; glc, GC-MS and GC-millimass techniques suggested it to be 5-chloro-2-ethoxy-1, 3, 2-benzoxathiaphosphole 2-sulfide. Practically, no significant differences were observed between the photoproducts formed by UV light and sunlight.

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To control pine wood nematodes (Bursaphelenchus xylophilus), chemical absorption, translocation and distribution of pesticides in the pine tree were studied. The treatment of Japanese pine with trunk injection of mesulfenfos (O, O-dimethyl O-4-methylsulphinyl-m-tolyl phosphorothioate) or soil incorporation of disulfoton (O, O-diethyl S-2-ethylthioethyl phosphorodithioate) was confirmed to be the most stable in effectiveness for the control of wilting disease caused by nematodes without phytotoxicity. Amounts of pesticides absorbed in the pine tree were determined by gas liquid chromatography (FPD). Both mesulfenfos and disulfoton were distributed vertically into the trunk and branch portions. Mesulfenfos was mainly found in the xylem and disulfoton was detected from xylem and phloem. The degree of control of pine wood nematodes was correlated with the concentration of pesticides in the pine tree. Detected compounds from the treated trees after trunk injection of mesulfenfos were mainly parent mesulfenfos. In the case of soil incorporation of disulfoton, oxidative products which are the sulfoxide and sulfone derivatives of disulfoton were found in the pine tree.

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Application of derivative spectrophotometry to residue analysis of thiophanate-methyl [dimethyl 4, 4′-o-phenylene-bis (3-thioallophanate)] (TM) was investigated. The results showed that derivative spectrophotometry was more suitable than ultraviolet spectrophotometry and high performance liquid chromatography which were already published. TM and its degraded product, 2-methyl benzeimidazoyle carbamate (MBC), were extracted together with methanol from crop and soil and transferred into methylene chloride. After evaporating the solvent, TM was converted to MBC by refluxing with copper acetate in 50% aqueous acetic acid. After liquid-liquid separation, 4th derivative spectrum of MBC in 1N hydrochloric acid was recorded by a Hitachi spectrophotometer type 330. The amount of MBC was proportional to the difference absorbance (ΔA=A₂₈₁-A₂₈₅) within the range of 0-0.5ppm. The detection limit of TM was 0.008ppm when 100g of sample was used. Recoveries of TM were 80% in crop and 87% in soil, respectively.

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Laboratory experiments were conducted to study the degradation of molinate (S-ethyl hexahydro-1H azepine-1-carbothioate) in three soils of different types under upland and flooded conditions using two kinds of ¹⁴C-molinate (labelled at S-ethyl-1-C and azepine ring-2-C, respectively) and non-labelled molinate. The degradation rates of molinate were more rapid and the ¹⁴CO₂ evolution was greater under upland conditions than under flooded conditions. The rates of degradation varied largely among the soils. In sterile soils, disappearance of molinate was very slow compared to the unsterile soils. Several degradation products of molinate were identified by tlc, GC and GC-MS. These were molinate-sulfoxide, azepine ring-4-hydroxy- and 4-oxo-derivatives, S-carboxyl methyl derivative and hexamethyleneimine which have been already reported, and azepine ring-2-oxo-derivative, S-2-hydroxyethyl derivative and ethane sulfonate which were newly recognized. The degradation pathways which contained oxidation of sulfur atom, azepine ring and S-ethyl moiety, and hydrolysis to yield hexamethylene imine and/or ethane sulfonate are proposed. Main degradation pathways were ring oxidation under upland conditions, and oxidation of S-ethyl moiety under flooded conditions. The relationship between molinate degradation and soil properties was also discussed.

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Binapacryl suspension concentrates were prepared by wet-grinding with an agitator mill, Attritor^®. In order to evaluate their long term physical stability, the changes of particle size, viscosity, sediment volume ratio and redispersibility were examined during storage at various temperatures. Although binapacryl was chemically stable in the suspension concentrates, the binapacryl particles started to grow markedly at 30°C or above and consequently undesirable changes in their physical properties occurred. No polymorphic change during the particle growth could be detected by X-ray diffractometry. From the observation on scanning electron micrographs of binapacryl particles at various intervals of time during the storage at 40°C, it was considered that the binapacryl particles adhered to each other by sintering and grew in size. The particle growth, however, could be reduced to an acceptable level by adding a small amount of finely ground water insoluble resins. Such a binapacryl suspension concentrate was physically stable either for 8 weeks at 40°C or for 28 months in a warehouse.

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Particle growth of binapacryl occurred at 30°C or above in the suspension concentrate prepared with technical grade binapacryl, while it appeared at 45°C or above in that prepared with recrystallized binapacryl. No polymorphic change during the recrystallization process could be detected by either X-ray diffractometry and DSC. However, it was confirmed that the acceleration of particle growth in the suspension prepared with technical grade binapacryl was attributable to 4, 6-dinitro-2-sec-butylphenol (DNBP), a main impurity contained in technical grade binapacryl. The particle growth of binapacryl in aqueous suspensions was affected by both temperature and the DNBP content in the disperse medium. In a DNBP content of more than 530ppm, the binapacryl particles started to grow at 30°C, while they began growing at 45°C in a medium with DNBP content of less than 130ppm. It was considered that DNBP existed mostly as fine particles in the medium. The melting point of DNBP (41.8°C) was lowered to approximate 25°C by mixing it with binapacryl. Therefore, it was estimated that DNBP particles which adhered to binapacryl particles easily became a liquid phase and might accelerate the bonding of binapacryl particles.

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Effect of guanidine hydrochloride on the residue analysis of guazatine triacetate [1, 1′-iminodi (octamethylene) diguanidine triacetate] is described. Guazatine triacetate residue in vegetables and fruits was extracted with 2N NaOH in MeOH with or without guanidine hydrochloride. The extract was transferred into chloroform and reacted with hexafluoroacetyl-acetone (HFAA) to form the bis (trifluoromethyl) pyrimidine derivative, which was determined by a gas chromatograph equipped with N-P FID. The value of recovery (87.3±5.5%) of guazatine triacetate (20ppm) from the guanidine hydrochloride-treated apple was significantly greater (p<0.001) than that (1.9±0.5%) from untreated apple. The limit of detection was 0.02ppm.

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Microsomal preparations from mycelial cells of a strain of Pyricularia oryzae designated as P-2 cleaved the P-S or S-C bonds in phosphorothiolate ester linkage of IBP (S-benzyl O, O-diisopropyl phosphorothiolate, Kitazin P^®) and formed diisopropyl phosphate (DIP) and diisopropyl phosphorothioate (DIPT). When the test fungus was cultured in the presence of phenobarbital, it strongly induced the formation of DIP, however the induction of DIPT formation by phenobarbital was weak in this experiment with a cell-free system. The cleavage reactions of P-S and S-C bonds require NADPH and oxygen for activity. Reduced microsomal preparations, when treated with carbon monoxide, showed maxima at 450 and 420nm. The inhibitors of mixed function oxidase, SKF-525A, piperonyl butoxide and carbon monoxide, and electron acceptors, cytochrome c and 2, 6-dichloroindophenol, suppressed the formation of DIP and DIPT. These results revealed the participation of mixed function oxidase in the cleavage of P-S and S-C bonds in IBP by mycelial cells of P. oryzae.

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Effect of several anti-blast chemicals on melanin biosynthesis in Pyricularia oryzae and influence on the pathogen of some metabolites related to the melanin pathway were studied. The results were: (1) 4, 5, 6, 7-Tetrachlorophthalide and PCBA (pentachlorobenzyl alcohol) influenced mycelial melanization as well as tricyclazole [5-methyl-1, 2, 4-triazolo(3, 4-b)benzothiazole] and CGA 49104 [1, 2, 4, 6-tetrahydro-4H-pyrrolo (3, 2, 1-i, j)quinolin-4-one], leading to enhanced accumulation of (+)-scytalone and 2-hydroxyjuglone in common. (2) Melanization in the appressoria of P. oryzae was also sensitive to these chemicals and appressorial penetration was impeded simultaneously. (3) 2-Hydroxyjuglone and scytalone interfered with appressorial penetration into the cellophane film at 10^-4 and 10^-3M, respectively. From the results described above and since appressorial invasion by P. oryzae into rice plant is at the most sensitive stage to those non-fungicidal chemicals, it is presumed that they act by a similar mechanism in the protection against fungal infection. The chemicals selectively inhibit appressorial penetration not only into rice sheath cells but also into artificial cellulose film, so that the present results suggest that the primary action of the protectants is on the pathogen and not on the host plant. Inhibition of melanization by the chemicals is supposed to be closely related to immaturity of the appressoria and to interference of the infection by P. oryzae. In addition, the abnormal accumulation of toxic metabolites such as 2-hydroxyjuglone and/or scytalone would offer an auxiliary explanation for the efficacy of the protectants.

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Application of derivative spectrophotometry to residue analysis of copper 8-quinolinolate in crops was investigated. The result showed that the derivative spectrophotometry was more suitable than colorimetry, atomic absorption spectrometry and high performance liquid chromatography which were already published. Copper 8-quinolinolate was extracted with acidic methanol from crops. After addition of 1% sodium chloride solution to the methanol extract, the mixture was washed with n-hexane. After neutralizing, the aqueous methanol solution was extracted with dichloromethane. Finally, the pesticide in the dichloromethane solution was re-extracted with 1N hydrochloric acid. Fourth derivative spectrum of the acidic solution was recorded by a Hitachi spectrophotometer type 330. The amount of copper 8-quinolinolate was proportional to the difference absorbance (ΔA=A₂₅₂-A₂₆₁) within the range of 0-0.3ppm. The detectable limit of copper 8-quinolinolate was 0.04ppm when 50g of sample was used. Average recovery was about 95%.

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[in Japanese]

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