Effective Concentration of Hydrogen Peroxide to Inhibit Phytophthora Zoospores During Irrigation Water Recycling

Abstract Reuse of excess irrigation water in horticulture is advisable for economic and environmental reasons. To combat spreading of phytopathogens during water recycling disinfection is common practice, one of the techniques is water treatment with hydrogen peroxide. Although the risk of spreading Phytophthora diseases by their water-motile zoospores is particularly high, the minimal inhibitory concentration of hydrogen peroxide against infection by Phytophthora zoospores has not been reported so far. By the means of an established sensitive bait test with Rhododendron leaves, virulence of hydrogen peroxide treated Phytophthora cactorum zoospores was tested. 150 ppm (4.41 mM) hydrogen peroxide was found as minimal inhibitory concentration of infection. It is concluded that this concentration is also valid for irrigation water to inhibit the virulence of Phytophthora zoospores towards potential host plants.