When dechlorination microbes in the diluted suspension of a soil activated for dechlorination of benthiocarb (thiobencarb, S-4-chlorobenzyl N, N-diethylthiocarbamate) were inoculated to several media, benthiocarb was rapidly dechlorinated after a lag period in an extract solution of reactive soil adjusted to pH 7 with phosphate buffer and in a mineral salt medium added with yeast extract or Bacto Casamino acid. Dechlorination, however, did not occur in usual bacterial media such as bouillon-peptone, V. L. basal and mineral salt medium. The concentration of minerals and organic nutrients in media greatly affected the lag period and the dechlorination rate. The dechlorination activity of soil extracts varied according to their components. The activity of extracts corresponded well to the activity of the original soils. Nitrogen concentration in media greatly affected the activity. Ferrous content in the soil extract was an essential factor for the growth of microbes. The concentration of organic nutrients and mineral salts and the ratio between them in media were also of great importance for the proliferation of dechlorination microbes.

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When the dechlorination-reactive soil was incubated with benthiocarb (thiobencarb, S-4-chlorobenzyl N, N-diethylthiocarbamate), a population of dechlorinating microbes, which was counted by the M. P. N. method, increased rapidly after a lag period of 15 days. Addition of starch into the soil resulted in great increase of the population. The population reached 30-fold the initial number after 44 days of incubation with benthiocarb in soil. Repeated applications of benthiocarb increased the population, but without benthiocarb it decreased rapidly. In soils with no dechlorination activity, no microbes were counted even after incubation with benthiocarb. Methoxyphenone and BNA-80, especially BNA-80 even at low concentration, inhibited the proliferation of the dechlorinating microbes for a long time, but not sterilized. The population of dechlorinating microbes always corresponded with the dechlorination activity of the soils.

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Interaction between organophosphates (OP) and housefly acetylcholinesterases (AChE) from the susceptible SRS strain and OP-resistant Daisan Yumenoshima (3-Y) strain was investigated. The ratios (3-Y/SRS) in half inhibitory concentration (I₅₀) of fenitroxon and salioxon were 46.2 and 4.6, respectively. This difference is the main reason of salithion's effectiveness against OP-resistant houseflies; the R/S ratios in the half lethal doses (LD₅₀) of fenitrothion and salithion were 259 and 8.2, respectively. The affinity of fenitroxon (1/K_d=0.77mM^-1) for 3-Y AChE was much lower than that of salioxon (1/K_d=3.55mM^-1). Fenitrothion took longer to kill OP-resistant flies and to inhibit their AChE in vivo than salithion. Fenitroxon-inhibited AChE's of both strains were reactivated more than 10% in vivo with an oxime-type reactivator, whereas salioxon-inhibited AChE's less than 5%.

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A way of action of the fenitrothion microcapsule as a residual spray formulation against cockroaches was studied. The microcapsule was prepared using polyurethane as a wall material (mass median diameter: 50μm, wall thickness: 0.14μm). The microcapsule was applied on a petri dish and the amount of fenitrothion outside the microcapsule was determined before and after cockroaches contacted with it. The results indicate that the spontaneous release of fenitrothion by diffusion through the capsule wall is not a main way of action, and that the microcapsule does not act as a stomach poison but as a contact poison. A main way of action of the microcapsule is trampling by cockroaches, which releases enough fenitrothion to kill tramplers.

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Flutolanil (α, α, α-trifluoro-3′-isopropoxy-o-toluanilide, Moncut^®) is a new fungicide primarily developed for control of rice sheath blight caused by Rhizoctonia solani. In green-house studies, it was remarkably effective against sheath blight by both protective and curative foliar spray at more than 25μg/ml with highly residual effects. The disease was effectively controlled by 80% at a concentration of 1.6-3.2μg/g. In addition, it exhibited acropetal movement in rice plants by both foliar spray and application to paddy water. In field studies, its foliar spray and dusting provided effective, long-term control over sheath blight.

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When regular dust (RD) and less-drifting dust (DL) of BPMC were applied to paddy fields by four kinds of boom-type blow heads, a large amount of the dusts discharged from a DL30A blow head deposited at the base zone of the pipe and a small amount at the end zone, a large amount of deposits from DMH30A and DLH30A remained at the end zone and a small amount at the base, and a large amount of deposit from Blow-in Green at the middle zone. The deposit distributions on the vertical surface showed a similar tendency to that on the horizontal surface, whereas coefficients of variation (CVs) were smaller. The horizontal deposit and vertical deposit were correlated and the slope of the regression line of RD was steeper than that of DL. Mortality of the brown rice planthopper was related with BPMC deposits. Higher correlation coefficients were observed in the relationship between the vertical deposit of BPMC and the insect mortality. The slope of dosage-response curves was steeper in RD than in DL. The average insect mortality was 81.6-84.3% for RD and 71.7-73.1% for DL. The amount of the insecticide floating in the air was two to three times larger by RD application than by DL application. The insecticide characteristics mentioned above suggest that RD is more effective than DL for control of the brown rice planthopper which lives at the foot of rice plants.

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The relationship between the formulation factors of microcapsule, particle size and wall thickness, and the residual contact efficacy against German cockroaches was studied using several kinds of polyurethane-walled microcapsules. All kinds of microcapsules were trampled by the contact with cockroaches, although the degrees of the trampling were different. Moreover the residual efficacy depended on the mass median diameter and the wall thickness. The D/T ratio (the ratio of mass median diameter (D) to wall thickness (T)) was proposed as a parameter of the strength of microcapsule; the higher the D/T ratio, the more the trampled microcapsule. The result led to a conclusion that the D/T ratio was closely related to the residual efficacy. The D/T ratio to optimize the initial and residual efficacy of microcapsule was around 150.

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The capacity of Pyricularia oryzae appressoria to penetrate onion epidermal walls was lost in an albino mutant or in wild type strains treated with melanin biosynthesis inhibitors, cerulenin, fthalide and tricyclazole. Melanization and penetration ability of cerulenin treated wild type or untreated albino mutant appressoria were restored with scytalone or 1, 8-dihydroxynaphthalene (1, 8-DHN). Fthalide or tricyclazole nullified the restoration by scytalone, but not by 1, 8-DHN. Penetration ability of wild type appressoria treated with 0.1μg/ml of fthalide or tricyclazole was restored by 1, 8-DHN, but was not well restored in appressoria treated with 1 or 10μg/ml of these inhibitors unless cerulenin was also present. This investigation indicates that blocking of the melanin biosynthesis pathway by fthalide or tricyclazole leads to two mechanisms of antipenetrant action (1) interference with melanin synthesis (2) accumulation of inhibitory metabolites. The latter mechanism, which may operate concomitantly with former, is nullified in the presence of cerulenin.

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Cytological effects of isoprothiolane (diisopropyl 1, 3-dithiolan-2-ylidenemalonate: IPT) on Pyricularia oryzae CAV, were investigated by applying it to protoplasts isolated from hyphae of IPT-sensitive (P2) and-tolerant (PI13) isolates. When protoplasts of the respective isolates were incubated in the presence of IPT at various concentrations, the number of P2 protoplasts decreased with time after the onset of incubation, while that of PI13 protoplasts was not affected, suggesting that the difference between P2 and PI13 in terms of tolerance to IPT might be associated with the difference between their symplasts. IPT concentration had no effect on the frequency of cell wall regeneration of both isolates, although it might interfere with the quality of the cell wall formed in the presence or absence of IPT. The most prominent effects of IPT on P2 were the suppression of reversion of hyphae at 10-25ppm and the complete inhibition of colony development at 5ppm. PI13 was not prominently influenced at either concentration. The results indicating the suppression of reversion are consistent with an earlier finding that IPT retards or inhibits mycelial growth. The present study demonstrated that the protoplast system could be used for cytological tests of fungicide effects.

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N-(2, 6-Dialkylphenyl)-4 (or 3)-carboxyphthalimides and the related compounds were prepared and their preventive activity against clubroot of Chinese cabbage caused by Plasmodiophora brassicae was examined. Among them, N-(2, 6-diisopropylphenyl)-and N-(2-s-butyl-6-ethylphenyl)-4-carboxyphthalimides were the most active. The preventive activity of the corresponding esters and amides varied significantly with variation of the alcohol and amine moieties. Relationships between the chemical structure and the preventive activity are described.

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The quantitative response of femur motor nerve preparations of two Japanese colonies, Mashiko and Mashiko-res 10, of pyrethroid-resistant houseflies was electrophysiologically compared with that of kdr, super-kdr and susceptible CSMA strains by applying several pyrethroids and DDT to the exposed thoracic ganglia of the flies. The ganglia of the Japanese strains were far less sensitive to both DDT and all Types I and II pyrethroids tested than those of the susceptible strain. Nerve response of the Mashiko-res 10 strain was similar to that of kdr or super-kdr strains. A quantitative difference was observed among the resistant strains in response to pyrethroids, but not to DDT. Pretreatment with the oxidase inhibitor piperonyl butoxide or the DDT-dehydrochlorinase inhibitor DMC did not alter the latency of appearance of symptoms and the firing frequency in motor nerve of the Mashiko-res 10 strain. It is concluded that nerve insensitivity plays a significant role in resistance to both pyrethroids and DDT in this Japanese strain of the housefly, although a possible involvement of other factor(s) can not be excluded.

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The fungicidal activity against rice blast, Piricularia oryzae, of 54 N-benzylacylamides having various substituents at the acid and amine moieties was determined in pot tests. The 1-(4-substituted phenyl) ethyl group on the nitrogen atom was necessary for the high activity. The variation in the activity of N-(1-phenylethyl)-2-bromo-3, 3-dimethylbutanamides having various benzene ring substituents at the 4-position was shown by the Hansch-Fujita method to be correlated with the variation in the hydrophobicity and electronic property of the 4-substituents. Both hydrophobicity and steric bulkiness of the substituents in the acyl moiety of N-[1-(4-chlorophenyl) ethyl] acylamides were also shown to be important in determining the variation in the activity. The R-configuration at both acid and amine moieties of N-[1-(4-chlorophenyl) ethyl]-2-bromo-3, 3-dimethylbutanamide was favorable to the activity.

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The study on the cuticular penetration of [methoxy-¹⁴C]phenthoate in the diamondback moth showed lower rates of Cuticular penetration, lower amounts of radioactivity in the insect body and higher excretion rates of phenthoate in the phenthoate-resistant strains (OSS-R and OKR-R) than in the susceptible strains (OSS and OKR). An in vivo metabolism study using [methoxy-¹⁴C] phenthoate revealed no apparent difference between resistant and susceptible strains in overall rates of metabolism of [methoxy-¹⁴C] phenthoate. The ¹⁴CO₂ produced by treated insects was too small in amounts to be considered as a major product of phenthoate metabolism. Such results of the study indicated that reduced Cuticular penetration of phenthoate is one of the important resistance mechanisms in the diamondback moth, Plutella xylostella L.

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The oxidative desulfurization of 2-methoxy-4H-1, 3, 2-benzodioxaphosphorin 2-sulfide (salithion) by m-chloroperbenzoic acid (MCPBA) produced an isomerized product 2-methoxy-4H-1, 3, 2-benzoxathiophosphorin 2-oxide (S-benzyl salithion) as well as the expected 2-methoxy-4H-1, 3, 2-benzodioxaphosphorin 2-oxide (salioxon). The isomerization was affected by reaction solvents; it proceeded easily in chloroform but was restrained by benzene and ether. Two derivatives of salithion, 6-chloro-2-methoxy-4-methyl-1, 3, 2-benzodioxaphosphorin 2-sulfide (CMMBS) and 2-ethoxy homolog (CEMBS), were also transformed into the respective S-benzyl isomers in different degrees by MCPBA. This type of isomerization was supposed to occur through a phosphorus oxythionate intermediate generally proposed for the MCPBA oxidation of P=S compounds. When incubated with a rat liver microsomal preparation, however, salithion did not yield any S-benzyl isomer.

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[in Japanese]

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[in Japanese]

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