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(249) Evaluation of methods to reduce the toxicity of storm runoff from California orchards. Werner, Inge1, Zalom, F.1, Oliver, M.1, Deanovic, L.1, Henderson, J.1, Oliveira, G.1, Angermann, T.1, Krueger, W.1, Hinton, D.1, Wilson, B.1, Wallender, W.1, 1 ABSTRACT- Organophosphorus (OP) insecticides, especially diazinon and chlorpyrifos, have been routinely detected in surface waters of the Sacramento and San Joaquin River watersheds in California, USA, coincident with storm events following their application to dormant orchards during the winter months. Risk assessment of environmental impacts of agricultural practices such as dormant pesticide sprays depend on the value of available toxicity and exposure data vis-à-vis the environmental practices studied. With this in mind, a team of integrated pest management and extension specialists together with hydrologists, chemists and toxicologists are quantitatively evaluating methods to reduce off site movement and toxicity of dormant sprays. Best management practices (BMPs) have been identified to mitigate the use of O Ps specifically. Use of BMPs mights also help prevent off site movement of other conventional pesticides. This study focuses on comparing the widely used, relatively water soluble OP, diazinon, and the increasingly applied, more hydrophobic pyrethroid pesticide, esfenvalerate ('Asana'). BMP scenarios include planting vegetation strips along waterways, creating berms to contain water on site, and maintaining orchard floor vegetation cover. Data on pest control efficacy, hydrological field modelling, runoff exposure levels and runoff toxicity to standard test species, fathead minnow (Pimephales promelas) and water flea (Ceriodaphnia dubia), and a native species, Sacramento splittail (Pogonichthys macrolepidotus), will be presented. Key words: pesticides, agricultural storm runoff, aquatic toxicity, best managament practices |
