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MA1 Methods in Risk Analysis
(007) Fate and effects of trifloxystrobin in drain channels of a banana plantation after aerial application.
Heimbach, Fred1, Pluecken, Udo2, 1 Bayer CropScience, Monheim, Germany2 Syngenta Crop Protection, Basle, Switzerland
ABSTRACT- In laboratory trials trifloxystrobin showed a high intrinsic toxicity to aquatic organisms, particularly to fish. Since laboratory results cannot be directly transferred to overspray field conditions, a study was performed under in-situ conditions in a banana plantation in Honduras, in order to evaluate the fate of trifloxystrobin and its metabolite trifloxystrobin-mono acid in the water and its effects on the aquatic community of drain channels. A wide strip of the plantation covering several primary and secondary channels was aerial oversprayed. Water samples were collected at representative points to determine the water concentration of trifloxystrobin and its metabolite over time. Additionally, observation of fish behaviour and survival after application and during the following days were performed. The study was carried out after the end of the second rainy season, when the water level in the channels was low, thus considering worst-case exposure conditions. The channels were 3 to 5 m wide with an open water surface of 0.2 to 4 m and a maximum water depth of 0.3 to 1.0 m. Channels were partly overgrown and the water flow within the channels differed according to the width of the water body. Several emerse plant species formed a dense vegetation at both sides of the channels. Submerse plants were noted in the open water, the water surface was partly covered with duckweed. Numerous distribution processes between water, plants and soil interfaces caused some delayin the release of trifloxystrobin and the metabolite to the water phase. Rain caused run-off from plants and soil, resulting in a secondary discharge into the water system. Trifloxystrobin was rapidly degraded: In stagnant water the half-life was 28 hours. In flowing water the dissipation was even more rapid due to additional dilution effects. Although at some sampling points the concentration of trifloxystrobin exceeded concentrations, which caused mortality under laboratory conditions, no effects on aquatic organisms, especially fish, were observed.
Key words: trifloxystrobin, banana plantation, degradation, aquatic organisms
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