Management of Phytophthora capsici and potential human foodborne pathogens in irrigation water
M. L. LEWIS IVEY (1), S. A. Miller (1)
(1) Ohio State University, Wooster, OH, U.S.A.
Phytopathology 101:S100

Contamination of surface water with plant pathogens and harmful human pathogens has the potential to reduce crop yield and lower the microbial quality of produce, respectively. In cooperation with local growers, the efficacy of commercial chlorine gas (Cl₂) and chlorine dioxide (ClO₂) irrigation water injection systems in killing human pathogens and Phytophthora capsici was evaluated. Using predefined parameters, irrigation water treated with Cl₂ was effective at reducing populations of coliforms and generic Escherichia coli to below EPA standards for recreational water at all sampling points in 2009, but only at the most distal emitter in 2010. The efficacy of ClO₂ in both years was variable with coliform levels never dropping below EPA standards. However, in 2010, generic E. coli populations were at acceptable EPA levels at the most distal emitter. Using baiting techniques in combination with P. capsici-specific PCR, P. capsici was detected in all the local irrigation water sources sampled but not on cucumbers collected from Cl₂ or ClO₂ treated or non-treated treated water in 2009. Many environmental factors contribute to the efficacy of Cl-based chemicals, including water temperature and pH and organic matter load. Finding ways to reduce the impact of these factors on the effectiveness of these treatments will be critical if such management strategies are to be both reliable and sustainable.