Isothymol, thymol and eugenol in the essential oil of Alpinia speciosa possess strong antifungal activity against plant pathogenic fungi. Although these active constituents are volatile in the natural environment, they can be changed into nonvolatile phosphorothionates by reaction with thiophosphoric agents using triethylamine or aq. NaOH as a base. Twenty-eight kinds of thiophosphorus esters were synthesized. During volatile testing, phenethyl alcohol and isothymol were almost volatilized in 9 and 14 days, respectively and eugenol was volatilized 89.2% in 14 days. Dimethyl isothymyl phosphorothionate (17), dimethyl eugenyl phosphorothionate (19), dimethyl phenethyl phosphorothionate (20), and diethyl phenethyl phosphorothionate (25) derived from each essential oil were scarcely volatilized and the volatility of 17, 19, 20, and 25 were 4.0, 2.3, 12.6, and 7.6% in 14 days, respectively. Among the synthesized compounds, 20 showed the strongest antifungal activity, 39.6 and 56.6% inhibition at 10ppm against Pythium sp. and Corticium rolfsii, respectively. Compound 20 had activity as potent as Iprobenfos.

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Sampling method was developed for analysis of various pesticides in the atmosphere using silica gel column (SEP-PAK™ cartridge) as adsorbent. Thirty eight pesticides were measured for the recoveries after fortification to silica gel, stability on silica gel under air passing, storage stabilities on silica gel and collection efficiencies of gaseous pesticides. The recoveries of pesticides fortified to silica gel column were over 96%. Fenthion and disulfoton on silica gel under air passing were unstable and it was presumed that they were decomposed by oxidation during the air passing. Edifenphos, simetryne, dimethylvinfos, tetrachlorvinfos and EPN were unstable in silica gel column at 25°C, then silica gel column was necessary to be kept under -15°C until extraction after collection of the air. The collection efficiencies of butamifos, dimethoate, piperofos and phosmet were not satisfactory, i. e. 45-60%. However, the other 32 pesticides have useful efficiency.

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Effects of buprofezin (Applaud^®) on the oviposition and the life span of Nilaparvata lugens were examined at sub-lethal doses. The reference compound, deltamethrin, enhanced the number of ovarioles, eggs laid and the life span of female adults, when insects were exposured to sub-lethal doses (0.4-0.00064ppm) of the chemical from 5th instar stage. On the other hand, buprofezin hardly increased or somewhat decreased the oviposition and the life span of female adults at sub-lethal doses (below 0.4ppm) in the same exposure-treatment as above. These properties of buprofezin probably play important roles in the prevention of the resurgence of N. lugens along with a little adverce effects on the natural enemies and non-target species.

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Pencycuron shows a specific inhibitory activity on the mycelial growth of Rhizoctonia solani. Even in the same anastomosis groups (AGs), e. g. AG4, there are both isolates sensitive and less sensitive (inherently resistant) to pencycuron. The regeneration of colonies from protoplasts of R-C (pencycuron-sensitive isolate in AG4) significantly decreased by the osmotic shock in the presence of pencycuron, while such effect was cancelled by washing off the chemical prior to the osmotic shock. However, in Rh-131 (a less sensitive isolate in AG4), the application of the chemical appeared to stimulate the regeneration from protoplasts. Further the measurement of optical density of protoplasts suspensions was performed to elucidate the effect of pencycuron on the osmotic stability of protoplasts in a short period. The optical density of suspensions of R-C protoplasts rapidly declined in a short period of incubation by the osmotic shock in the presence of pencycuron, but the effect on Rh-131 protoplasts was not statistically significant regardless of the presence or the absence of the chemical. These results suggest that the cell membrane of the pencycuron-sensitive isolate (R-C) is specifically affected by pencycuron.

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Wild oat (Avena fatua L.) is one of the most troublesome weeds in wheat (Triticum aestivum L.) and difficult to control because of its adaptability and competitiveness to wheat. Diclofop-methyl has been extensively used to control postemergence wild oat. The herbicidal activity of diclofop-methyl is less than the recent aryloxyphenoxypropionate herbicides. Some newly synthesized derivatives of 2-[4-(3, 5-dichloro-2-pyridyloxy)phenoxy]propionamidoxyacetic acid showed selectivity between wheat and wild oat. In these compounds, N-ethyl-2-[4-(3, 5-dichloro-2-pyridyloxy) phenoxy]propionamidoxyacetamide (23) showed higher herbicidal activity against wild oat than diclofop-methyl and a comparable selectivity between wheat and wild oat.

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Degradation of imazosulfuron, 1-(2-chloroimidazo[1, 2-a]pyridin-3-ylsulfonyl)-3-(4, 6-dimethoxypyrimidin-2-yl)urea, in the flooded soils was studied under laboratory conditions using the compounds labeled with ¹⁴C at imidazopyridine and pyrimidine rings. Imazosulfuron showed significant difference in degradation rates between aerobic and anaerobic conditions, and disappeared from the soils with half-lives of approximately 60 and 3 days, respectively. Imazosulfuron was subjected to the cleavage of sulfonylurea bond and monodemethylation to give 2-amino-4, 6-dimethoxypyrimidine (ADPM), 2-chloroimidazo[1, 2-a]pyridine-3-sulfonamide (IPSN) and 1-(2-chloroimidazo[1, 2-a]pyridin-3-ylsulfonyl)-3-(4-hydroxy-6-methoxypyrimidin-2-yl)urea (HMS) as the major degradation products. ¹⁴C-carbon dioxide gradually increased with time accounting for 11.0-48.3% and 1.6-4.4% under aerobic and anaerobic conditions, respectively, for the period of 360 days. In the sterilized soils under aerobic and anaerobic conditions 30 days after the treatment, the degradation rate of imazosulfuron and amounts of degradation products except for HMS were similar to those observed in nonsterilized soils under aerobic conditions 30 days after the treatment. Imazosulfuron in the soils under aerobic conditions gradually disappeared with time by the hydrolysis of the sulfonylurea bond to give ADPM and IPSN, and finally mineralized to carbon dioxide. On the other hand, imazosulfuron under anaerobic conditions was degraded by soil microorganisms, followed by conversion to soil organic matters.

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An ester of the acid moiety of kadethrin, one of pyrethroid insecticides, with a photoreactive alcohol containing a diazirine group was synthesized as a probe for elucidating the target site of pyrethroids. Its insecticidal potency against American cockroaches agreed well with the value predicted from a correlation equation that was previously established by quantitative structure-activity analysis for a set of esters of the acid with meta-substituted benzyl alcohols. The compound modified the membrane potentials of crayfish and cockroach giant axons, inducing depolarizing afterpotentials as well as depolarizing the resting membranes. The inward sodium currents in the crayfish giant axon and rat pituitary tumor cells, GH₃, were also modified by the compound. Decay of the current was slowed to induce a residual current, associated with enhancement and prolongation of the tail current.

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The influence of 1, 2-alkylene-1, 2, 4-triazolidines and 3, 4-alkylene-1, 3, 4-thiadiazolidines on peroxidizing phytotoxicities was investigated using corn etioplast protoporphyrinogen-IX oxidase (Protox), autotrophic Scenedesmus acutus cells and Echinochloa utilis. Both types of compounds inhibited Protox, caused ethane formation, decreased chlorophyll content and inhibited growth of Scenedesmus and root-growth of Echinochloa, like peroxidizing herbicides such as p-nitrodiphenyl ethers and cyclic imides. All compounds were identified as peroxidizing herbicides. Among the 1, 2-alkylene-1, 2, 4-triazolidines, tetramethylene-triazolidines exhibited the strongest peroxidizing phytotoxicity, trimethylene-triazolidines and pentamethylene-triazolidines were found to be less active peroxidizers. The tetramethylene moiety of the triazolidine-type compounds appears to be essential for producing active peroxidizing compounds. Phytotoxicities by triazolidin-one-thiones and triazolidine-dithiones were more than 10 times stronger than those of triazolidine-diones. Replacing carbonyl groups in the five-membered moiety by at least one thiocarbonyl group produces stronger peroxidizing phytotoxities. Although the Protox inhibition of triazolidine-peroxidizers was 10-70 times stronger than that of the corresponding thiadiazolidine-peroxidizers, the level of other phytotoxic activities was quite similar with both types of peroxidizers. This fact may be caused by isomerization of thiadiazolidines to triazolidines.

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Twenty-nine N-[5-(substituted phenyl)-1, 3, 4-thiadiazol-2-yl] benzamides with various substituents on both benzene rings were synthesized. Most of them inhibited the incorporation of N-acetyl-[1-¹⁴C]-glucosamine into cultured rice stem borer (Chilo suppresssalis WALKER) integument in the presence and absence of a metabolic inhibitor for oxidative degradation, piperonyl butoxide. Variations in the activity under each experimental condition were quantitatively analyzed with physicochemical substituent parameters and regression analyses. After the separation of the hydrophobic effect, para substituents on the benzene ring at the 5-position of the thiadiazole ring showed peculiar electronic and steric effects on the inhibitory activity. The greater the inductive component of the electron-withdrawing property and the molecular hydrophobicity, the higher the activity. Introduction of electron-donating groups such as OMe and Me at the ortho position of the benzoyl moiety seemed to be favorable to the activity. A limited number of compounds showed larvicidal activity against the insects via topical application.

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The activity of the four elicitors, a N-acetylchitopentaose [(GLNAc)₅], a chitopentaose [(GLN)₅], Ag⁺ ion and victorin, which induce phytoalexins in oats were compared using the following assays: i) electrolyte leakage, ii) effects of Ca²⁺ on the induction of phytoalexin and iii) difference in induced-metabolite profiles. The results suggest that at least two distinct mechanisms are involved in phytoalexin induction in oats. Among the tested elicitors, (GLNAc)₅ appears to induce phytoalexin directly by binding to its putative receptor, while induction by other elicitors may be a secondary effect, presumably due to the damage of the plasma membrane caused by the elicitors.

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[in Japanese]

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[in Japanese]

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