Fire blight of apple extension12/28/2023 In late summer (after bacterial oozing no longer occurs), prune all diseased wood at least 6 to 8 inches below the infection, surface sterilizing tools between cuts. To manage the disease, improve plant vigor, but avoid heavy spring fertilization that would promote succulent growth. As the disease advances, cankers form at the base of infected branches, and highly susceptible plants may die.Ĭonditions optimal for fireblight development are extended periods of warm (greater than 65 to 75 F), wet weather during spring. Twigs and branches infected with the pathogen die rapidly and appear scorched, hence the name “fireblight.” Tender shoots tend to droop and bend as they die, developing a symptom commonly associated with the disease called a shepherd’s crook. Erwinia bacteria penetrate tissue through wounds and natural openings such as stomates and nectaries. Insects are especially attracted to this sweet, sticky, bacterial ooze bees and other pollinating insects commonly pick up bacteria while visiting the cankers and subsequently deposit the cells on developing flowers. These cells are spread to susceptible flowers, leaves, fruit, and stems by insects, wind, splashing rain, or pruning equipment. Some common hosts include apple, crabapple, cotoneaster, hawthorn, mountain ash, pyracantha, and pear.ĭevelopment of fireblight usually begins in the spring as bacterial cells ooze in a yellow-amber liquid from existing cankers on infected plants. Fireblight is caused by Erwinia amylovora, a bacterium that only affects plants in the rose family (Rosaceae). ![]() ![]() Recent reports bring to mind that warm and wet spring weather is perfect for development of the bacterial disease known as fireblight in susceptible hosts.
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