Pythium Root Rot

    Pythium spp.


    Roots infected with Pythium (Donald Groth, Louisiana State University AgCenter,


    Overwatered plants infected with Pythium (Paul Bachi, University of Kentucky Research and Education Center,


    Pythium root and stem rot symptoms (Howard F. Schwartz, Colorado State University,

    Hosts, Symptoms & Signs

    • affects annual and perennial bedding plants
    • wilting plants
    • roots are brown or black and look rotten

    Disease Cycle

    • Pythium is common in many soils and only some species are pathogenic to plants under wet conditions
    • Pythium spores are able to swim in a film of water toward a root
    • Pythium spores enter the root, kill and feed upon it

    IPM Recommendations

    • Plant disease-free plants to prevent Pythium introduction.
    • Clean tools to prevent moving Pythium from one part of the garden to another.
    • Prevent excessive soil moisture or standing water as Pythium infects plants under those conditions.
    • Remove diseased plants.