Microbial Degradation of Herbicide Pentoxaxone in Soils
The degradation of pentoxazone, 3-(4-chloro-5-cyclopentyloxy-2-fluorophenyl)-5-isopropylidene-1,3-oxazolidine-2,4-dione, was investigated in two types of paddy field soils under flooded conditions using the compounds labeled 14C at the phenyl ring. Pentoxazone was moderately metabolized to various degradation products and finally mineralized to CO2. The amount of evolved 14CO2 ranged from 8% to 23% of dosed radioactivity. When soils were sterilized, the degradation rates of pentoxazone were apparently slower than those without sterilization and no 14CO2 evolution was observed. This indicates that most of the degradation and successive mineralization have been performed by soil microorganisms. Major degradation pathways in flooded soils were proposed to include: hydrogenation of the isopropylidene moiety to 3-(4-chloro-5-cyclopentyloxy-2-fluorophenyl-5-isopropyl-1,3-oxazolidine-2,4-dione (A-0089), hydrolysis of the oxazolidine ring to N-(4-chloro-5-cyclopentyloxy-2-fluoro-phenyl)-3-methyl-2-oxobutanamide (A-0505) and its successive reduction to N-(4-chloro-5-cyclopentyloxy-2-fluo-rophenyl)-2-hydroxy-3-methylbutanamide (A-1374) and oxidative decyclopentylation to 3-(4-chloro-2-fluoro-5-hydroxyphenyl)-5-isopropylidene-1,3-oxazolidine-2,4-dione (A-1347). Additional investiga-tions demonstrated faster degradation of pentoxazone and more extensive evolution of 14CO2 under up-land condition. The major metabolites were A-1347 and further methylation product, 3-(4-chloro-2-fluoro-5-methoxyphenyl)-5-isopropylidene-1,3-oxazolidine-2,4-dione (A-1292). These results suggest that aerobes play an important role in the mineralization of pentoxazone in paddy field soils.
Key words: soil microorganisms, pentoxazone, degradation, mineralization, adsorption.
Measurement of Pesticides Leaching by Using Pan Lysimeter Method on a Sandy Upland Field (in Japanese)
Extent of pesticides leaching was measured by using the pan lysimeter method on a sandy upland field in Chiba Prefecture, Japan. A collecting pan (30×30 cm) in the lysimeter was installed into the soil profile horizontally at 50 cm below the soil surface. Total volume of leachate and its ratio to the total rainfall during the monitoring period (125 days) was 608.2 mm and 65%, respectively. Daily average volume of leachate was increased by two heavy rains. Test chemicals were dimethoate, simazine, metolachlor, diazinon, chlorotharonil, and Cl- as a tracer. Among five pesticides, only dimethoate and simazine were detected in the leachate. Maximum concentrations of dimethoate and simazine were 18.4 ppb and 1.0 ppb, respectively. The dimethoate concentration in leachate reached maximum when Cl- concentration in leachate began to rise. The simazine concentrations in leachate were lower with delayed detection periods and a broader elution profile when compared with those of dimethoate. During the monitoring period, the total mass of pesticide leaching and its ratio to the application rate for dimethoate were 2.99 mg/m2 and 3.5%, respectively. The corresponding values for simazine were 0.33 mg/m2 and 0.4%, respectively. Daily average amount of dimethoate leaching was significantly increased by the first heavy rain.
Key words: pesticides leaching, sandy upland field, pan lysimeter method, dimethoate, simazine, Cl-.
Adsorption and Desorption of Herbicide Imazosulfuron in Soils
Adsorption and desorption of imazosulfuron in soils were investigated using the compound labeled 14C at pyrimidine ring. Batch soil adsorption study of imazosulfuron was conducted using five kinds of soils in Japan, and the adsorption equilibrium time was found to be 2 hr. Freundlich adsorption coefficients of imazosulfuron showed range from 0.96 to 5.27. Desorption constants of imazosulfuron in two kinds of soils were determined 0, 7, 30 and 60 days after treatment, and were 0.98 and 15.7 on day 0, and increased with time up to 35.8 and 37.0 on day 60. From these findings, it was suggested that imazosulfuron was found to be hardly desorbed from the soils with time.
Key words: imazosulfuron, labeled compound, soil adsorption, soil desorption, herbicide.
Development of a Small-Scaled
Model Test System for Simulation of Pesticide Runoff
A new indoor runoff test system with controlled rain conditions was developed to better understand the field surface runoff mechanism. Containers (0.7 m2) packed with soil of plow layer were used as test plots and placed under a rain-making machine (10‐80 mm/hr) at a 5° slope. When rain conditions of a field (840 m2) in runoff were simulated to the test plot after pesticide application (a mixture of chlorothalonil, diazinon and dimethoate), not only amounts of runoff water (l/m2) but also concentrations of runoff pesticides were very similar to those of the field runoff. When the water runoff in the field was predicted by the occurrence conditions in the indoor runoff test system, amounts of predicted runoff water were larger than the collected ones. Some model tests were performed with 30 mm/hr of rainfall and 1 l of runoff water collection. When individual test plots were aged for several periods (1‐21 days) after pesticide application, the concentrations of pesticides in water samples decreased with the lapse of time after aging. Furthermore, when concentrations and ratios of runoff pesticides from each test plot with and without plants were compared, the small difference was observed between the test plots with and without plants.
Key words: rainfall, rain-making machine, pesticide runoff, model test.
Spray Ununiformity Observed in Nozzle Motion Spraying Pesticide on Eggplants (in Japanese)
A pesticide was sprayed in a field of V-shaped training eggplants (height: 2.2 m) by a grower with the conventional method such that the motion of a nozzle drew a wavy curve, and the distribution of pesticide adhesions on leaves was investigated. Also, the level of pesticide adhesion during a wavy motion (wavelength: 2 m, wave height: 1 m) of the nozzle was studied under the condition in which a pesticide was sprayed onto a side of a row of eggplants. The maximum quantity of pesticide adhered on the underside of leaves which were located on the line of spray during the upward motion of the nozzle (Location A). On leaves located on the line of spray during the downward motion (Location B), the mean quantity of pesticide was less than 10% of that on the leaves in Location A. In other locations which were located aside from the line of spray, the quantity of pesticide was below the detectable level. The maximum quantity of pesticide adhesion on the topside of leaves occurred on the leaves in Location B. There was a reasonable level of pesticide adhesion on the leaves in Location A and in Location D which was surrounded with the upward and downward line drawn by the motion of the nozzle. The minimum quantity of pesticide adhesion occurred on the leaves in Location C which was surrounded with the downward and upward line. The number of western flower thrips on the underside of leaves depended on the quantity of pesticide adhesion. Pesticide spraying to both sides of the plants did not change the above results. When the colouring solution was sprayed, it was obvious that the direct adhesion was 40 cm wide along the line of spray, but it almost didn't in the other area. These results show that spray ununiformity occurs during the upward and the downward motion of the nozzle, as well as among leaves which are located on or aside from the line of spray.
Key words: eggplant, spray ununiformity, motion of nozzle, line of spray, pesticide adhesion.
Effect of Cyromazine Fed to Adults on Reproduction and Offspring Development in Housefly
The effect of cyromazine on reproduction, egg hatch and subsequent larval development in the housefly was studied by administering cyromazine in concentrations up to 1000 ppm in adult drinking water. Larval survival was completely inhibited by the continuous feeding of 500 or 1000 ppm cyromazine to newly emerged adults and the effect was exerted predominantly through female. When the cyromazine feeding was limited to the first four days after emergence, the inhibitory effect on larval development was observed only at the first gonotrophic cycle. In any combinations of the cyromazine treatment, the egg production, egg hatch, pupa formation and adult emergence were not affected.
Key words: insect growth regulator, IGR, cyromazine, housefly, Musca domestica, effect on reproduction and development.
Adsorption Rate Equation of Herbicides in Paddy Soils
It is vital not to under evaluate the adsorption rates of paddy herbicides, which influence their movement in the soil and water for environmental safety and agricultural practice. The adsorption rates of four herbicides, esprocarb, thiobencarb, pretilachlor and simetryn, in three kinds of paddy soil whose properties varied widely were investigated. It was found that the herbicides were absorbed in the soils in two steps characterized by fast and slow phases. The ratios of the fast adsorption α were independent of the initial concentration for each tested system of herbicide and soil. Then an adsorption rate equation was introduced from α and the approximated Boyd equation and its applicability was confirmed. The rate parameters of the slow adsorption Dｉ′/r2 were obtained in the range of 3.4×10-7 to 7.3×10-7/s by the proposed equation. The differences among the herbicides and the soils were small.
Key words: paddy herbicides, paddy soils, adsorption, rate equation.
Synthesis and Fungicidal Activities of (α-Methoxybenzyl)isoxazoles
A series of (α-methoxybenzyl)isoxazole derivatives (I) were synthesized and their fungicidal activities were assessed. Studies of the structure-activity relationship revealed the strongest fungicidal activity when the isoxazole moiety was comprised of a 3-methyl-5-isoxazolyl group. When position-2 of the phenyl ring in the benzyl moiety was substituted with a 4-phenyl-2,3-diaza-1,3-pentadienyl group, good fungicidal activity was achieved. When the benzene ring in the 4-phenyl-2,3-diaza-1,3-pentadienyl moiety was substituted with a 4-bromo, 4-trifluoromethoxy or 3,4-dichloro group, good fungicidal activity was obtained. Among the 29 compounds examined, 5-[2-{4-(4-bromophenyl)-2,3-diaza-1,3-pentadienyl}-α-methoxybenzyl]-3-methylisoxazole (23) showed potent activities against cucumber powdery mildew and cucumber downy mildew.
Key words: (α-Methoxybenzyl)isoxazole, alkoxyiminoacetamide, strobilurin, fungicidal activity, powdery mildew, downy mildew.
Repellent Effect of Garlic against Stored Product Pests
Intact garlic clove, grated garlic and its volatile extract applied on brown rice showed a repellent effect but no insecticidal activity against two stored product pests, i.e. the maize weevil and the red flour beetle. Neither repellency nor insecticidal activity was observed with garlic or its extract against two agricultural pests, diamondback moth larvae and green peach aphids. In comparative tests, hot pepper and "wasabi" mustard demonstrated only weak repellency, if any, although volatile components of "wasabi" mustard showed insecticidal activity against these insects. Volatile components of garlic were trapped and subjected to GC-MS analysis. Four major peaks resolved were sulfide compounds produced by the rapid degradation of allicin and a cyclic compound produced by dehydration. It remains to be determined whether allicin itself, the degradation products, or the mixture of these are responsible for the repellent effect.
Key words: garlic, stored-product pests, repellency, volatile compounds.
Synthesis and Precocious Metamorphosis-Inducing Activity of 3-(1-Alkenyl)pyridines
A series of 3-pyridine derivatives with an 1-alkenyl group was synthesized and evaluated against 4th instar (penultimate) larvae of the silkworm, Bombyx mori, for their activity to induce precocious metamorphosis. Of the compounds tested, 3-(2-methyl-1-phenyl-1-propenyl)pyridine (18) was the most active, indicating that both a phenyl substituent at the 1 position and a short alkyl chain at the 2 position in the ethenyl moiety were significant for activity. Precocious pupation induced by 18 was accompanied by the prolongation of the larval period and the increase of body weights. Both 20-hydroxyecdysone and methoprene, a juvenile hormone agonist, could fully counteract precocious metamorphosis induced by 18. When applied to newly molted 4th instar larvae, 18 suppressed the increase of hemolymph ecdysteroid titers leading to larval ecdysis to 5th instar. These results indicated that 18 acted as an anti-ecdysteroid agent and temporarily depressed the ecdysteroid titer in the hemolymph to induce precocious metamorphosis.
Key words: precocious metamorphosis, 3-pyridines, ecdysteroids, Bombyx mori.
Synthesis and Fungitoxic Activity of N-Cinnamoyl-α-Amino Acid Esters
Key words: N-cinnamoyl-α-amino acid ester, cinnamic acid, fungitoxic activity, Pythium sp., Corticium rolfsii.
Fungitoxic and Phytotoxic Activities of Cinnamic Acid Esters and Amides
Key words: hcinnamate, cinnamamide, fungitoxic activity, phytotoxic activity, Pythium sp., Corticium rolfsii.
Effects of Enantiomerism on Fungicidal and Insecticidal Activities of (α-Methoxybenzyl)isoxazoles
Key words: (α-Methoxybenzyl)isoxazole, enantiomerism, fungicidal activity, insecticidal activity.
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