Fire Blight

    Fire Blight

    Erwinia amylovora

    fire blight

    Fire blight-killed branch (William Jacobi, Colorado State University, Bugwood.org)

    fire blight

    Bacterial ooze from fire blight (Marion Murray, Utah State University Extension)

    fire blight

    Fire blight stem canker (Marion Murray, Utah State University Extension)

    Hosts, Symptoms & Signs

    • Rosaceae (rose family)
    • spring: flowers turn brown and die
    • spring: shoots/leaves will start to die back from the tip; the tip is sometimes bent forming a “shepherd’s crook”
    • older infections develop cankers on large branches or the main trunk
    • cankers look wet when bacteria are oozing from them

    Disease Cycle

    • overwinters within infected tissues at canker margins
    • disease growth begins in spring when the tree breaks dormancy
    • bacterial ooze from cankers can be splashed by water or transmitted by bees and flies during pollination
    • the bacteria is spread during bloom to blossoms and anytime to shoots through natural openings or damage
    • trees remain susceptible to infection until new growth stops; succulent growth (e.g., root sprouts) can be infected anytime

    IPM Recommendations

    • Manage trees to improve or maintain overall health.
    • Prune infected shoots 12 inches below the symptomatic area to remove the bacteria that have moved beyond the symptomatic part of the shoot.
    • Disinfect pruning tools between cuts using a 10% bleach or 70% alcohol solution or disinfecting wipes. If tools are not disinfected, fire blight could be spread to healthy plants during pruning.
    • Apply copper products during the dormant season on cankers.
    • Apply antibiotics in spring to prevent blossom infections.
    • Visit climate.usurf.usu.edu/traps to view the fire blight risk forecasting system to assess risk for ornamental trees.