The relationship between the photolysis rate of naproanilide and irradiation wavelengths was investigated. The photolysis rate (conversion per unit energy) was higher under 340nm ultraviolet irradiation than under the wavelengths longer than 35nm, when measured by conversion per unit energy (cal/cm²). The molar absorptivity was high (about 1000) at 310-330nm and low (less than 30) at 350nm, showing the photolysis rate is related to the absorptivity. When the photolysis rate was measured by time, the relationship between the photolysis rate and irradiation wavelengths was not clear. The process of naproanilide photolysis was fitted to a pseudo first-order kinetic at an energy (cal/cm²) of 300-340nm with a xenon lamp. The difference in the reaction rate between at 10°C and 30°C was very small. The photolysis rate of the granule formulation was lower than that of the active ingredient in water, indicating that the photolysis in a paddy field takes place when naproanilide is relased from a granule.

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The photodegradation of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (2, 3, 7, 8-TCDD), 1, 3, 6, 8-TCDD and 1, 2, 3, 4-TCDD in 1, 4-dioxane solutions was studied under xenon lamp irradiation. Only reductive dechlorination reaction was observed in the photodegradation of TCDDs. 2, 3, 7-Trichlorodibenzo-p-dioxin (2, 3, 7-TrCDD), 2, 7-dichlorodibenzo-p-dioxin (2, 7-DCDD), 2, 8-DCDD, 2-monochlorodibenzo-p-dioxin (2-MCDD) and dibenzo-p-dioxin (DD) were identified as the photodegradation products by GC-MS in the photodegradation of 2, 3, 7, 8-TCDD. 1, 3, 6-TrCDD, 1, 3-DCDD, 1, 6-DCDD, 1-MCDD, 2-MCDD and DD were identified in the photodegradation of 1, 3, 6, 8-TCDD, while 1, 2, 3-TrCDD, 1, 2, 4-TrCDD, 1, 2-DCDD, 1, 3-DCDD, 1, 4-DCDD, 2, 3-DCDD, 1-MCDD, 2-MCDD and DD in the photodegradation of 1, 2, 3, 4-TCDD. In the Photodegradation reaction, chlorine atoms in the 2, 3, 7 and/or 8-positions were dechlorinated more rapidly than those in the 1, 4, 6 and/or 9-positions.

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The photodegradation of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (2, 3, 7, 8-TCDD), 1, 3, 6, 8-TCDD and 1, 2, 3, 4-TCDD in 1, 4-dioxane solutions was investigated under xenon lamp irradiation. In a wavelength range of 199.8nm to 397.9nm, each of the TCDDs showed two maximal photodegradation peaks after 200-min irradiation. In the 2, 3, 7, 8-TCDD solution, one of the maximal photodegradation peaks was observed at 252.6nm, and the other in a wavelength range of 292.1nm to 332.0nm. In both 1, 3, 6, 8-TCDD and 1, 2, 3, 4-TCDD solutions, one of the maximal photodegradation peaks was at 252.6nm, and the other at 305.6nm. Since the energy spectrum of xenon arc is close to that of sunlight, it is likely that sunlight energy intensity affects the photodegradation of 2, 3, 7, 8-TCDD, 1, 3, 6, 8-TCDD and 1, 2, 3, 4-TCDD in the environment to a large extent at 313.6, 305.6 and 305.6nm, respectively.

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In our random screening program we have happened to find a family of pyrimidinylhydrazones that are toxic to fungi and may be able to be potent fungicides. Further investigation on their relatives in our chemical bank and the derivatives synthesized in this study will pave the way to develop new fungicides for agricultural use. Our studies have made it clear that 2-pyrimidinylhydrazones with sterical congestion in the vicinity of the hydrazone bond and alkyl substituent (s) on the pyrimidine ring have fungicidal activity high enough to be developed for practical use.

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In an attempt to determine the absolute configuration of 4-methyl-1-nonanol, a sex attractant of the yellow mealworm, Tenebrio molitor L., both enantiomers were synthesized. The enantiomers and the natural attractant were converted to diastereomeric derivatives. The pheromonal activity of both enantiomers and the retention times of the derivatives on HPLC were compared with those of the natural attractant and its derivatives. The natural attractant was found (R)-(+)-4-methyl-1-nonanol.

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Two fenvalerate-selected strains (KAR₈₄-FR and OKR₈₄-FR) of the diamondback moth, Plutella xylostella (L.) resistant to fenvalerate (racemic) >500-fold showed resistance to fenvalerate A (S-isomer) and fenvalerate B (R-isomer) as well. Studies on cross resistance revealed that the KAR₈₄-FR strain was low in cross resistance to phenthoate, prothiophos, cyanophos and methomyl, and that the OKR₈₄-FR strain was particularly low in cross resistance to these insecticides. Both fenvalerate-resistant strains showed a slight tolerance to acephate and dichlorvos but no cross resistance to cartap. Synergism of piperonyl butoxide (PB) and triphenyl phosphate (TPP) with fenvalerate A was high against both resistant strains at synergist ratios (SR) of LD₅₀>17. Higher synergisms of TPP with fenvalerate A at LD₅₀ levels were observed in the susceptible strains (KAR₈₄ and OKR₈₄) than in the resistant strains, while higher synergisms at LD₉₅ levels were shown in the resistant strains than in the susceptible strains. On the other hand, synergisms of sesamin, sesamol, episesamin and S-421 with fenvalerate A were low in the KAR₈₄-FR strain, while apparently high in the OKR₈₄-FR strain.

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A research program leading to the discovery of an agricultural fungicide, ferimzone (common name proposed to 8b), was initiated when an interesting fungicidal activity was observed in pyrimidinylhydrazone 1a in our random fungicidal screening. Ferimzone, (Z)-2′-methylacetophenone 4, 6-dimethyl-2-pyrimidinylhydrazone (8b), is a new fungicide with curative activity, which is effective against rice blast, leaf brown spot, stem-rot, and sheath blight by foliar treatment. The synthesis of a host of analogs and their fungicidal properties are described.

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Two minor components of host-selective pathotoxins, ACTG-toxins G and H, and a novel sesquiterpene, Compound A, were isolated from the culture broth of Alternaria citri, a fungus that produces brown spot disease of Dancy tangerine (Citrus tangerina Hort. ex Tan.) and other mandarin cultivars (Citrus reticulata). Structures of ACTG-toxins G and H were determined to be anhydro-ACTG-toxins A and F, respectively. Structure of Compound A, including its absolute configuration, was determined to be dihydrosporogen AO-1.

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A variety of benzanilides with a dihydrofuran, tetrahydronaphthalene or indane ring were synthesized, and their fungicidal activities against rice sheath blight were studied. Of the compounds tested, N-(1, 1-dimethyl-4-indanyl)-2-(trifluoromethyl) benzamide was the most effective, showing the importance of substituents at the 1-position of the indanyl systems. The examination on its preventive and curative effects revealed that N-(1, 1-dimethyl-4-indanyl)-2-(trifluoromethyl) benzamide was a promising fungicide whose activity was higher than mepronil and flutolanil.

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The influence of formulation factors of fenvalerate microcapsules, particle size and wall thickness on insecticidal efficacy against Plutella xylostella and Spodoptera litura and fish toxicity to Olyzias latipes was studied. The insecticidal efficacy of the microcapsules was affected by parameter D/T, the ratio of mass median diameter (D) to wall thickness (T), which was considered to be related to the strength of microcapsules. The fish toxicity of the microcapsules was affected by parameter D·T, the multiplication of D and T, which was considered to be related to the release rate of fenvalerate encapsulated in microcapsules. These results suggest that a very important factor to prepare excellent microcapsules for agricultural use with high insecticidal efficacy and low fish toxicity is to control parameters D/T and D·T.

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[in Japanese]

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Pesticides are required to satisfy the following conditions at present: (1) a high safety standard, (2) high efficacy, (3) low prices. Screening probability of new pesticides has decreased and it has become extremely difficult to develop new ideal pesticides. In such a situation, improvement in formulations and application technologies weigh a lot in order to satisfy the above conditions. Labor-saving on spraying is also desired. As a means to meet such demands, various studies have been done on new pesticide formulations. Developments of new pesticide formulations and new application fields for existing pesticides would be comparable to inventions of new pesticides. Besides, the cost and time required for such developments would be less than those for the developments of new pesticides. From the viewpoint of economization the evaluation of new formulations for existing pesticides will be more favorable. With this understanding, we have been working to develop various kinds of new pesticide formulations. Fenitrothion microcapsule (MC) has been developed for control of cockroaches, termites and insects that attack plywoods. The main way of action of fenitrothion MC against cockroaches was trampling. When trampled by cockroaches, fenitrothion was released burstly to kill them just like a land mine destroys a tank. Also an eating mechanism was involved to some extent. The contact efficacy depended on the strength of the MC and the diameter/thickness (D/T) ratio. To termites, the main way of action was biting and sticking to appendages, followed by self- and mutual-grooming. When used for plywood panels, fenitrothion was stabilized in alkaline phenol resin to give longer residual efficacy. Pyrethroid MC was applied to agricultural uses, in which the biological efficacy depended on D/T, phytotoxicity and rain fastness on T, fish toxicity and acute toxicity on D×T. Fenvalerate and fenitrothion concentrated emulsions were developed by using suitable water-soluble polymers as dispersing agents. Main characteristics of the formulation was the decrease in toxicity and irritation, and the decrease in drift phenomena. Procymidon dry flowable was formulated by the spray drying method. This formulation was less phytotoxic, and physicochemical properties were favorable. Solid EC was formulated by using hydrolized starch. Flo-dust was shown to be usable as wettable powder as well. Calcined synthetic hydrated silicone dioxide improved the residual efficacy of fenitrothion wettable powder for residual spray application. When polyethyleneglycol or polypropyleneglycol was used in the EC formulation without any emulsifiers, acute toxicity and irritation reduced. Thermal decomposition mechanisms of organophosphorous insecticides and pyrethroids were clarified and stabilization methods were proposed. In the near future, research on pesticide delivery systems and the developments of various kinds of functional formulations will become important in order to meet recently growing demands for a higher safety standard, higher efficacy, lower prices, more labor-saving, better formulation properties and the development of new application fields.

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Etofenprox is a new synthetic insecticide discovered and developed by Mitsui Toatsu Chemicals, Inc. In 1979 we began searching for a compound with insecticidal activity, comparable to existing pyrethroids, but with low toxicity to fish as to be used in paddy fields. While examining a new active substance after repeatedly testing a number of hypotheses and ideas, we found a lead skeleton that has ether linkage within the molecule, not ester linkage as in the case of existing pyrethroids. Then we tried to optimize the insecticidal activity around the lead skeleton, and as a result, 2-(4-ethoxyphenyl)-2-methylpropyl 3-phenoxybenzyl ether (etofenprox) was selected as a candidate for development. It is now registered for agricultural use in Japan and some countries in Southeast Asia. Etofenprox is a compound composed of carbon, hydrogen and oxygen only, and effective as a contact and stomach poison against many kinds of insect pests in crops, animals and public health fields. Etofenprox has several favourable properties compared with conventional insecticides: It is low in acute mammalia toxicity and fish toxicity, high in compatibility with other pesticides, causes no skin and eye irritation, has a small impact on natural enemies, no phytotoxicity, no cross-resistance to carbamates and organophosphorous insecticides, no BPH resurgence.

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[in Japanese]

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