PARENT SESSION
66 - Pesticide Ecotoxicology
2:10 PM to 5:20 PM, Wednesday, 15 May 2002
Session Chair: Nagel, Roland ¹, Zok, Sabine ², ^{1 2} .
Lehar A

(66-01) Mitigation of pesticide-associated runoff in vegetated agricultural drainage ditch systems.

Bennett, Erin^*,1, Moore, Matt², Charles, Cooper², Smith, Sammie², Farris, Jerry³, Milam, Cristi³, Schulz, Ralf⁴, Letcher, Robert¹, ¹ Great Lakes Institute for Environmental Research, Windsor, Ontario² USDA-ARS, Oxford, MS³ Ecotoxicology Research Facility, Jonesboro, AK⁴ Technical University, Braunschweig, Germany

ABSTRACT- Vegetated agricultural drainage ditches have been proposed as a new best management practice to mitigate potential effects of agricultural contaminants associated with storm runoff. Annual studies conducted since 1998 have indicated the importance of ditch vegetation as a medium for the transfer of pesticides out of the aqueous phase, thereby mitigating potential risks to downstream aquatic receiving systems. Two ditches within the Mississippi Delta Management Systems Evaluation Area (MDMSEA) have been utilized for simulated storm events examining the fate and toxicity of various types of pesticides associated with runoff. Ditch vegetation had greater initial success (3 h post simulated event) in transferring aqueous pyrethroid and organophosphate insecticides as opposed to triazine herbicides (i.e. 94-99 percent and 61 percent, respectively). For the herbicide, 86 percent was associated with plants 28 d following the simulated event. In addition to fate data, toxicity evaluations were conducted to track movement of pesticides down the ditches during simulated events. These evaluations have provided data indicating remediation of contaminated ditch water and sediment following simulated storm events. Simple regression analyses of environmental data indicated that ditches can effectively mitigate pesticides within reasonable ditch lengths (50 to 400 m), depending upon contributing drainage area and assumed rainfall and runoff percentages. These data provide further information on the importance of vegetated agricultural ditches as an inexpensive mitigation tool for the reduction of potential non-point source threats to downstream aquatic receiving systems. Pesticide fate and toxicity research is ongoing on these vegetated ditch systems in Mississippi, USA and will be further applied in an agricultural region in southern Ontario, Canada.

Key words: agricultural ditches, insecticides, herbicides, mitigation