![]() Once a shoot is infected, the fire blight bacteria multiply rapidly and droplets of ooze can be seen within three days. Shoot infections can also occur through wounds created by sucking insects (aphids, leafhoppers or tarnished plant bugs), freeze or frost damage, wind whipping, wind-driven rain, or hail. These bacteria multiply rapidly in the blossom nectar, and spread to the spurs (blossom-bearing twigs), new shoots and branches, resulting in secondary infections. Relatively few overwintering cankers become active and produce bacteria in the spring, but a single active canker may produce millions of bacteria, enough to infect an entire orchard. Primary infections (Figure 2) are initiated during bloom when bacteria are carried from the cankers to open flowers by splashing rain, pollinating insects (i.e., bees, pollen wasps, flies, ants) or during production practices such as pruning. Precise environmental conditions are needed for infection to occur and as a result disease incidence varies considerably from year to year.įire blight bacteria overwinter as cankers in living tissue on the trunk and main branches and on mummified fruit. Rain, heavy dews and high humidity favor infection. List of commonly grown plants in Ohio that are susceptible to fire blightįire blight first appears in the spring when temperatures get above 65 degrees F. While young trees can be killed in a single season, older trees can survive several years, even with continuous dieback.įigure 1. On apples and pears, the disease can kill blossoms, fruit, shoots, twigs, branches and entire trees. The disease is caused by the bacterium Erwinia amylovora, which can infect and cause severe damage to many plants in the rose (Rosaceae) family (Table 1). ![]() ![]() Fire blight is a common and very destructive bacterial disease of apples and pears (Figure 1).
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