Phytophthora Root and Crown Rot

    Phytophthora spp.


    Wilt from Phytophthora infection (Daren Mueller, Iowa State University,


    Discoloration and crown rot (Ontario Ministry of Agriculture, Food and Rural Affairs, Queen's Printer for Ontario)


    Root rot caused by Phytophthora (William M. Brown Jr.,


    Hosts, Symptoms & Signs

    • many deciduous trees and shrubs; some conifers
    • tree or shrub starts wilting, then dies
    • rotten roots
    • lower stem areas can be discolored and rotten
    • motile spores can swim in a film of water to spread

    Disease Cycle

    • soilborne pathogen; it can live in decaying matter until a suitable host is planted
    • spores will swim to the roots, often being attracted by root exudates
    • spores enter the root and colonize it; in the process they kill the roots and feed on the dead tissue
    • spores formed in the dead roots are released as the roots decompose

    IPM Recommendations

    • Avoid introduction of pathogens into the garden by cleaning tools and planting healthy, disease-free plants.
    • Plant trees and shrubs in well-drained soils.
    • Plant Phytophthora-resistant plant species if the disease is present in the soil or where a plant has previously died from Phytophthora infection.
    • Infected plants should be removed with as much of the roots as possible and disposed of in the trash.