The action of probenazole (Oryzemate^®), 3-allyloxy-1, 2-benzisothiazole-1, 1-dioxide), a rice blast controlling agent, on several stages of the life cycle of blast fungus was investigated. Anti-microbial activities against twenty-six species of plant pathogens including the blast fungus in vitro were weak. In contrast, when the inside of the rice leaf sheath was inoculated with conidia suspended in 10ppm of probenazole solution, a high inhibitory effect against the penetration was observed. Also a high inhibitory effect against the appressorial formation and penetration was observed in vitro employing cellophane membrane. Inhibitory effect against the growth of mycelia in a lesion and sporulation were observed more evidently in the experimental system in vivo than in vitro. Therefore, it was quite plausible that the strong controlling effect of probenazole against blast disease by the submerged application is the integrated effect of these inhibitory actions including the strong inhibitory effect against the penetration. The inhibitory actions of the transformed products of probenazole was generally weaker.

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The compound-eye tissues containing corneal lens and crystalline cone of the Bombay locust, Patanga succincta Johansson, transmitted visible and near ultraviolet light (UV) longer than 280nm, while the vertebrate (bovine) eye transmitted only visible light of 380nm or longer wavelengths. From this, the near UV ranging from 280nm to 380nm could be considered to have a vital significance to the insect vision and no significance to the vertebrate vision. The photosensitivity and dark reactions of retinyl-thiazolidine-4-carboxylic acid, an insect UV receptor model, indicated that the chemicals such as L-cysteine and hydroxylamine could be considered as the model compounds disturbing the normal function of near UV in the insect eye under dark condition and photosensitive chemicals such as the complexes formed from retinal and L-cysteine or hydroxylamine could be considered as the model compounds giving selective damages to the structure and function of the insect eye upon absorbing near UV. This selectivity was suggested to be utilized as new possible action mechanism of insect-controlling chemicals.

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For radiation disinfestation of harmful insects in imported timbers, the radiosensitivities of ambrosia beetles, such as Xyleborus perforans, Xyleborus atratus, and Xyleborus semiopacus, which have been frequently found in timbers from Southeast Asia were studied. These three species of ambrosia beetles were reared by an artificial medium composed of lauan sawdust, starch, dried yeast powder, sucrose, and distilled water with a small amount of streptomycin. Lethal doses on 3 to 4-day-old female adults were determined on the 12th day after gamma irradiation. The LD₅₀ and LD₉₉ of X. perforans were 57krad and 90krad, respectively. Dose required for inhibition of adult emergence from pupae of X. perforans was more than 8krad. The sterilizing dose to pupae of X. perforans was 3-5krad. When male adults which had emerged from irradiated pupae were mated with unirradiated female, only male adults emerged in the following generation. This observation suggests that the dose enough to inactivate the sperm of this parthenogenetic insect is 3-5krad. The sterilizing doses to mated female adults of X. perforans, X. atratus, and X. semiopacus were 4krad, 4krad, and 2krad, respectively. Irradiation of female adults of X. perforans with 5-10krad produced only male adults in the following generation. In cases of irradiation of both female pupae and mated female adults, propagation of ambrosia fungus was retarded with increasing doses.

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To improve Ames' chemical carcinogen screening test system, several species of animals including rats, mice, guinea pigs, hamsters and rabbits were pre-treated with polychlorinated biphenyl (PCB), 3-methylchoranthrene (MC) and phenobarbital (PB), and hepatic S-9 fraction obtained therefrom was tested as to the effects on the increase of revertant colonies of S. typhimurium TA98 and TA100. Among 12 strains of the 5 mammalian species, S-9 fraction from PCB-treated Hartley guinea pig proved to be more effective than that from PCB-treated SD rat in detecting three different types of mutagens, Benzo (a) pyrene, 2-acetylaminofluorene and dimethylnitrosamine. The methylcholanthrene-pretreated guinea pig (Hartley) liver S-9 was equally effective to the rat preparation and PCB-treated hamster S-9 fractions were effective to DMN mutagenesis, whereas Wistar and Fisher rats, ICR and dd mice and rabbits were generally no better than SD rat.

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A gas chromatographic method for the selective determination of a guanidino fungicide, guazatine (DF-125; 1, 17-diguanidino-9-azaheptadecane acetate), in the rice grain was developed. The compound was extracted from the rice grain with 0.5N NaOH/MeOH partitioned into chloroform, and treated with hexafluoroacetylacetone (HFAA), to give bis [3, 5-bis (trifluoromethyl) pyrimidyl-1-amino]-8, 8′-dioctylamine. The pyrimidine analogue of guazatine thus obtained was determined by FTD gas chromatography. The lower limit of detection of this method was 1ng, corresponding to 0.05ppm in 5g of sample. Overall average recovery from the rice grain was ca. 90%.

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Effects of 3, 3′-dimethyl-4-methoxybenzophenone (NK-049) on the biosynthesis of photosynthetic pigments in higher plant leaves were studied under different light conditions and the following results were obtained: 1) NK-049 completely inhibited the accumulation of both chlorophylls and carotenoids under strong light to yield white seedlings, while an appreciable amount of chlorophylls and carotenoids were accumulated under weak light, which were decomposed rapidly on exposure of the pale green leaves to strong light. 2) Accumulation of protochlorophyllide and its photoconversion to chlorophyllide α in etiolated leaves were not influenced by NK-049, whereas the carotenoid accumulation was strongly inhibited in darkness as well as in the light. 3) Some intermediates involved in the biosynthesis of β-carotene were accumulated in the dark-grown or dim light-grown seedlings. 4) It was concluded that NK-049 specifically inhibits the dehydrogenation process in carotene biosynthesis, which leads to the photodecomposition of chlorophylls under strong light to result in chlorosis.

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Some biological characteristics of a new chemical class of selective miticides, cycloprate (ZARDEX^®, ZR-0856, hexadecyl cyclopropanecarboxylate) against the citrus red mite, Panonychus citri (McGregor), were investigated. High ovicidal activity of the compound was observed against eggs of all stages; most embryos died at the pharate larval stage. Delayed ovicidal effects resulted in larval death soon after hatching. Insecticidal activity was most pronounced in the larval stage and decreased in further developmental stages. The death of nymphs occurred mostly during molting. A sterilizing activity against female adults was shown from both egg hatch and the survival of hatched larvae, but this was only a transient effect. These facts suggest that the mode of action of cycloprate might be quite different from that of other miticides in current use.

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A method of residual analysis of a new herbicide, naproanilide, α-(2-naphthoxy) propionanilide, and its degradation product, naphthoxypropionic acid (NPA) was established. Both compounds in rice grain or rice straw were extracted with acetone and the solvent was distilled off under vacuum. The residues were dissolvent in n-hexane and extracted with acetonitrile. The solution was diluted with basic water and propanilide was extracted with ether. NPA was extracted with dichloromethane after the aqueous solution was acidified with hydrochloric acid. Then the residues were cleaned up by column chromatography as follows. Compound naproanilide was applied to a Florisil column and eluted with n-hexane containing 30% of ether. NPA was applied to a silica gel column and eluted with a mixture of n-hexane, ether and acetic acid (100:100:0.5). When rice straw was used as the sample, further cleanup process by column chromatography using silica gel as adsorbent was required. The determinations of both compounds were performed on a high speed liquid chromatograph fitted with a glass column (3mm×50cm) packed with Hitachi-gel #3010. Methanol and methanol containing 0.25% of acetic acid were used as eluting solvents for naproanilide and NPA, respectively, at a flow rate of 1.5ml/min. A fluorophotometer with a flow cell (2×20mm) was used as the detector. Wave length for excitation was 280nm and that for emission was 340nm. Any interfering peak was not found in chromatograms obtained in analyses of rice grain and rice straw. The lower limits of detection of each compound were 0.004ppm (grain) and 0.008ppm (straw), so this method was as sensitive as ECD-gaschromatography. The recovery ranged between 74 and 99%.

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Diazinon is effective for control of soil insects such as scarabs larvae. However, sometimes it does not give an expected effect. This study deals with the difference in insecticidal activity of different formulations. Equal amount of the active ingredient was used in every formulation. To compare the penetrable activity of diazinon formulations, these were applied to turf, and the activity was tested by a new laboratory test method designed by us. This method does not destroy soil structure. Emulsifiable concentrate was the most active formulation. Wettable powder was less active than emulsibiable concentrate. Granule was found to have no penetrable activity, even when the soil was irrigated every day for a month. Field tests also led to the same result. These experiment proved that different formulations had different insecticidal activities against insects in deeper soil. The results suggest that the selection of suitable pesticide. formulation is of importance, and that the suitable screening method is required for the selection.

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From extracts of fresh leaves of Leucothoe catesbaei, grayanotoxin I (1) and III (2) and poriolide (3) and isoporiolide (4) were isolated as insecticidal and antimicrobial constituents, respectively. This is the first report to show the presence of these compounds in the plant.

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Effects of several fungicides, active against rice blast, on the penetration by Pyricularia oryzae were studied in vitro by using cellophane film as a model of plant cell walls. The fungus penetrated the film by infection pegs emerging from appressoria (appressorial penetration) and partly by hyphal tips (hyphal penetration). Some fungicides known to be nontoxic against spore germination, appressorium formation, and mycelial growth affected selectively the appressorial penetration but not hyphal one. Effects of fungicides on appressorial penetration seem to be useful to explain the disease-control activity of fungicides.

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[in Japanese]

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[in Japanese]

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