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Title: Utilization of common ditch vegetation in the reduction of fipronil and its sulfone metabolite

item Moore, Matthew

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2008
Publication Date: 11/5/2008
Citation: Kroger, R., Moore, M.T. 2008. Utilization of common ditch vegetation in the reduction of fipronil and its sulfone metabolite. Pest Management Science. 64:1212-1217.

Interpretive Summary: Pesticides leaving agricultural fields can contaminate aquatic receiving systems such as rivers, lakes, or streams, causing harm to fish and other animals. Experiments were conducted to determine if various aquatic plants can sorb certain pesticides commonly associated with runoff and remove the pesticides from the water column. Four different types of aquatic plants were exposed to fipronil, an insecticide used in cotton and rice. After dosing the plants with fipronil-contaminated water for 4 hours, no difference in pesticide removal was noticed between any of the four plants and the non-vegetated control system. Additional experiments will examine potential mitigation using lower initial pesticide concentrations, increasing the amount of contact time the pesticide has with the plant, and the use of different aquatic plant species.

Technical Abstract: Fipronil, a phenylpyrazole insecticide and its oxidative sulfone metabolite are two potential nonpoint source pollutants from treated rice and cotton production. A consequence of these pollutants occurring in surface runoff is degradation of downstream aquatic ecosystems. Utilization of primary intercept drainage ditches as management practices to reduce fipronil concentrations and loads has not been examined. This study used ditch mesocosms planted with monospecific stands of common emergent wetland vegetation to determine if certain plant species were more proficient in fipronil mitigation. Three replicates of four plant species were compared against a non-vegetated control to determine any differences in water column outflow concentrations and loads. There were no significant differences between vegetated and control treatments in outflow concentrations (F4,8 = 0.35, p = 0.836) and loads (F4,8 = 0.35, p = 0.836). The range of fipronil reduction was 28-45% for both concentration and load. Unlike fipronil, fipronil sulfone concentrations and load increased by 96 – 328%. The increase in fipronil sulfone was a direct consequence of fipronil oxidizing in the mesocosm. The type of ditch vegetation had no effect on fipronil reduction. Future research needs to examine initial concentrations and hydraulic retention times to examine potential changes in reduction capacities.