Journal of Pesticide Science

The improved version of the pesticide paddy field model (PADDY) was evaluated for the prediction of pesticide concentrations in water and soil considering water balance on the water management. Field studies under the two different conditions on the water management practices, continuous irrigation and drainage, and water holding management that regulate drainage during the experimental periods, were performed to validate the improved model using molinate and simetryne. For both pesticides, concentrations in paddy water were the same level during the first day after the application on both fields. After second day, pesticide concentrations on the field for continuous irrigation and drainage were lower than those on the field of water holding management. Good fits between model predictions and field observations were obtained for the two pesticides by considering the water management and hydrological condition.

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A simazine resistant biotype of Poa annua L. was found in a golf course in Shizuoka prefecture, Japan. The biotype was highly resistant to s-triazines, almost equally susceptible to the phenylurea, diuron, and more susceptible to the phenol, dinoseb, than the susceptible biotype both at whole plant and at isolated thylakoid levels. The molecular basis of resistance to s-triazine herbicides in the resistant biotype was identified as a mutation in psb A gene giving rise to the replacement of serine 264 by glycine in the D1 protein of photosystem II (PS II). The resistant biotype showed a reduced capacity of photosynthesis when grown under full-sunlight conditions. However, no differences were observed in photosynthetic performance of susceptible and resistant biotypes when grown under shaded conditions. The resistant biotype also showed increased sensitivity to photoinhibition both at whole plant and at isolated PS II membrane levels, indicating that the increased susceptibility in the resistant biotype to the photoinhibition is due to the substitution of serine 264 to glycine in the D1 protein.

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The effect of pH, water hardness and temperature in water on release profile of time-controlled release granule (TCRG) was investigated. The release profile of metominostrobin from TCRG did not change regardless of changing pH from 4 to 10 and water hardness from 3 to 100. However, as the temperature increased, the lag time was shortened and the release rate became faster. When the logarithmic cumulative temperature was plotted as abscissa and release percentage as ordinate, the release profiles measured at fixed temperatures (15, 20, 25, 30°C) and changing temperatures from 15 to 30°C periodically were superposed. Therefore, the released percentage could be predicted from cumulative temperature. Thus, it was thought that the difference in water permeation through PVC membrane by temperature caused different release profiles.

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The various efficacy of acetamiprid granule against the cotton aphid on cucumber plants according to several different applications such as planting hole and soil-surface applications was investigated. In planting hole application, the uncontrolled-release granule showed excellent efficacy when treated at the center of hole dug in soil as well as when treated uniformly in the hole. In case of soil-surface application, the efficacy of the granule exhibited higher activity against the aphid as the distance between the treated point and the foot of the transplanted seedling became shorter within the distance of 5, 10 and 20cm from the foot of the seedling. The relationship between the efficacy and distance of treated points was the same as in the uncontrolled-release granule. Besides, the influence of the watering volume on the activity was examined. With planting hole application, the activity with lower watering-volume plots was higher than that with higher watering one within the watering volume designed. On the other hand, with soil-surface application the activity against the aphids was inferior to that with planting hole application. Moreover, the effect of watering volume and kind of soil on the activity of the controlled-release granule with planting hole application was examined. It was indicated that a relation between the efficacy and watering volume varied by the kind of soil.

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