Infections initiated in blossoms and shoots can continue to expand both up and down larger branches and limbs. Numerous diseased shoots give a tree a burnt, blighted appearance, hence the disease name ( Figure 4). Leaves on diseased shoots often show blackening along the midrib and veins before becoming fully necrotic. Tips of shoots may wilt rapidly to form a 'shepherd's crook' ( Figures 1 and 3). Shoot symptoms are similar to those in blossoms but develop faster. Ooze droplets are initially creamy white, becoming amber-tinted as they age. During periods of high humidity, small droplets of bacterial ooze form on water-soaked and discolored tissues ( see example on fruit, Figure 7). Similar symptoms often develop in the base of the blossom cluster and young fruitlets as the infection spreads internally ( Figure 2).

Later these tissues shrivel and turn brown to black. The floral receptacle, ovary, and peduncles become water soaked and dull, grayish green in appearance. Blossom clusters and young shootsīlossom symptoms are first observed 1-2 weeks after petal fall. Generally, symptoms of fire blight are easy to recognize and distinguishable from other diseases. Symptoms of fire blight can be observed on all above ground tissues including blossoms, fruits, shoots, branches and limbs, and in the rootstock near the graft union on the lower trunk. Today, fire blight is an important disease of apples and pears in many parts of the world. It was the first bacterium proven to be a pathogen of plants. HOSTS: Apple, pear, several rosaceous ornamentalsĮrwinia amylovora is a native pathogen of wild, rosaceous hosts in eastern North America.

Apple tree fire blight