Fire Blight

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.