Total Hg in rice and total, soluble and organic Hg in soil were determined by atomic absorption spectroscopy. An Hg trap was devised for the rice digestion. Soluble Hg was extracted with 0.3% thiomalic acid solution, and determined under alkaline conditions after breaking down the thiomalic acid with H₂O₂. The extract with 0.3% thiomalic acid solution was acidified with HNO₃, reduced with SnCl₂ and aerated for removing inorganic Hg followed by the determination of organic Hg under the alkaline condition. Paddy soils sprayed fungicides containing mercury in a usual way contained about 1.5 times Hg than those never sprayed the fungicides. After nine years from the application of phenylmercuric acetate (PMA) equivalent to the amount to be used for 100 years, the paddy soil contained 7.2ppm of total Hg, 0.21ppm of soluble Hg, and 0.033ppm of organic Hg and rice contained 0.062ppm of total Hg. Total, soluble and organic Hg in soil and total Hg in rice in the paddy soil where PMA was not applied, were 0.37ppm, 0.020ppm, <0.004ppm and 0.011ppm respectively. A linear relationship exists between the soluble Hg in soil and the total Hg in rice from the paddy field mixed with PMA. Amounts of organic Hg in the soils tested were within the range of <0.004ppm to 0.055ppm irrespective of Hg application.

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Thiosemicarbazides were examined for control effect against bacterial leaf blight of rice caused by Xanthomonas oryzae as a root application. The 1-lower alkyl thiosemicarbazides were found to be fairly effective against the disease. Significant disease control activity in this series was found only for 1-methylthiosemicarbazide. 1-Methylthiosemicarbazide was able to control the disease as a root application at extremely low dosage whether it was applied preventively or curatively and its duration of effect was fairly long. Any phytotoxicity was not observed on rice plant when the chemical was applied at high dosage twenty times as much as enough dosage to control the disease. It was able to use mixing with other insecticide, fungicide and herbicides as a paddy water application. However, 1-methylthiosemicarbazide showed no control effect as a foliar spray and exhibited no antibacterial activity against Xanthomonas oryzae on agar medium.

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N-p-Fluorophenyl-2, 3-dichloromaleimide (MK-23) is effective against rice blast, cucumber anthracnose, tomato late blight, citrus melanose, and citrus scab. Experiments were conducted to investigate the fungicidal activity of this compound on each stage of the fungal life cycle of Pyricularia oryzae, i. e. spore germination, appressorial formation, hyphal growth, and sporulation. And the inhibitory effects on several types of metabolism, i. e. O₂ uptake, protein synthesis, RNA, DNA synthesis, lipid synthesis, and cell wall synthesis were investigated. The inhibitory activity of MK-23 to spore germination or appressorial formation was extremely high, although that to hyphal growth or sporulation was poor. The ED₅₀ for spore germination and appressorial formation were 0.011 and 0.012mM, respectively. Sulfhydryl compounds such as glutathione and dithiothreitol reduced the inhibitory activity of MK-23 against spore germination and the incorporation into the spore of substrates such as ¹⁴C-amino acids, ¹⁴C-thymidine, ¹⁴C-uracil, ¹⁴C-glucose, ¹⁴C-glucosamine, and ¹⁴C-sodium acetate. It is assumed that MK-23 reacts with cellular sulfhydryl compounds and specificially inhibits spore germination.

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Three structurally related pigments, rugulosin (Rug) and skyrin (Sky) which are products of Endothia parasitica, and luteoskyrin (Lut) which is a well-known mycotoxin produced by Penicillium islandicum, were tested for their inhibitory effects on rice dwarf virus (RDV) RNA transcription and E. coli DNA-dependent RNA polymerase activities, using in vitro assay systems for both enzymes. Lut inhibits only E. coli RNA polymerise but has no effect on RDV-RNA transcriptase. Rug strongly inhibits E. coli RNA polymerase but weakly RDV-RNA transcriptase. Conversely, Sky inhibits RDV-RNA transcriptase without inhibiting E. coli RNA polymerise. The Mg²⁺-mediated complex formation of Lut and Rug with DNA and that of Rug with RDV-RNA may account for their inhibitory effects on both enzymes, however this is not true with Sky on DNA and Sky on RDV-RNA. Sky forms complex with Mg²⁺ because its absorption spectrum shifts to longer wave lengths with increasing amounts of Mg²⁺ added but the complex does not form floccules which can be seen in Lut-Mg²⁺ and Rug-Mg²⁺ mixtures. Sky-Mg-DNA and Sky-Mg-RDV-RNA mixtures do not form such a complex which can be precipitated by centrifugation at 59, 000×g for 20min. Sephadex G-25 column chromatography of the mixtures indicates that nucleic acids are completely separated from Sky-Mg complex. When RDV-virions are pretreated with Sky and Mg²⁺, pelleted by centrifugation, then added to the reaction mixture, RDV-RNA transcriptase is not inhibited at all, whereas inhibited strongly by the addition of the supernatant which contains Sky. These results suggest that Sky inhibits RDV-RNA transcriptase not by its direct action to RDV-RNA present in virions but by its contact with virions at the site of transcription.

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Many S, S′-disubstituted and S, S′-cyclic substituted derivatives of bis (alkoxycarbonyl) ketene dithioacetal were prepared and their rice blast controlling activities were investigated. Though some of the S, S′-disubstituted derivatives showed good activities, they did not possess systemic fungicidal activity. In the S, S′-cyclic substituted derivatives, only 1, 3-dithiolane derivatives showed excellent activities. In the systematic changes of ester moieties in the dithiolane derivatives, diisopropyl 1, 3-dithiolan-2-ylidenemalonate was found as the most desirable compound which showed excellent activities as well as strong systemic action.

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A new method, low volume application by fine dust formulations in green houses has been developed. The formulations whose mean diameters were under 5μ were applied at the rate of 300-500g/10a from the entrance of green house by knapsack-type power applicator. Fine dust applied had good floating ability and was deposited a large amount even on the back of plant leaves. The application showed flat diffusion of dust in green house having an areas of 200m² and 1, 000m². Polyvinyl chloride film as covering material was contaminated only slightly. Application time per 10a was about 5 minutes. Application of diazinon fine dust formulation (a. i. 20%) at 500g/10a gave 100% mortality against Myzus persica of egg-plant in large green house. Application of chlorothalonil fine dust formulation (a. i. 30%) at 500g/10a has resulted as good control effect as application of chlorothalonil wettable powder in Celletotrichum lagenarium of cucumber in large green house.

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Carbon-14 Sumithion, fenitrothion or O, O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioate labeled at m-methyl group of the phenol moiety was added at 10ppm to 2 kinds (Utsunomiya and Moriyama) of silty loam, Katano sandy loam and Muko sandy soil, and kept at 25°C in the dark under upland and submerged conditions. Under upland condition fenitrothion is decomposed with half lives of 12 to 28 days depending on the kind of soil. 3-Methyl-4-nitrophenol and radioactive carbon dioxide are major decomposition products. 3-Methyl-4-nitrophenol formed during early period of incubation amounts to 10-20% of the total radioactivity, while the amount of carbon dioxide reaches approximately 40% after incubation for 60 days in Utsunomiya and Muko soils. Under submerged condition decomposition of fenitrothion is even more rapid, and aminofenitrothion, major product, is produced quite rapidly; in Moriyama and Katano soil 50-70% of fenitrothion is converted to aminofenitrothion is 10 days. 3-Methyl-4-nitrophenol and carbon dioxide are minor products.
Both fungi (Fusarium sp.) and bacteria (Bacillus sp.) isolated from Utsunomiya or Moriyama soil rapidly metabolize fenitrothion, majorly to aminofenitrothion, and as minor products are identified 3-methyl-4-nitrophenol, desmethylfenitrothion, 3-methyl-4-aminophenol, formylaminofenitrothion and acetylaminofenitrothion.
Fenitrothion and its radioactive decomposition products are hardly eluted with water from the application site in the above 3 loamy soils, while in Muko soil with low organic matter and low clay content the radiocarbons are loosely bound to the soil and migrate easily with moving water.

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Antimicrobial spectrum of N-(3′, 5′-dichlorophenyl)-1, 2-dimethylcyclopropane-1, 2-dicarboximide (S-7131) was studied in vitro. Although S-7131 was quite innocuous to yeast, bacteria and fungi belonging to Phycomycetes, the fungicide was found to be remarkably effective against some species in Ascomycetes and a few in Deuteromycetes. S-7131 was remarkably effective, both protectively and curatively, against cucumber gray mould and bean Sclerotinia rot diseases in pot tests. In addition, the fungicide exhibited high persistency in fungitoxicity and considerable systemic activity both in foliar and root applications. Absorption of the fungicide through the roots of cucumber seedlings and its translocation into the cotyledons was quantitatively determined by utilizing a bioautographic technique. The fungicide was translocated into cotyledons rapidly after a lag period of a few hours.

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[in Japanese]

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