Noticed any branches of your pear or apple trees that look like they’ve been torched or scorched? Might be a case of fire blight, a nasty bacterial disease. It most frequently affects pome fruit trees (apples and pears) and related plants – crabapple, ornamental pear, pyracantha, and quince.
Infections may appear scattered throughout the crown of the plant and exhibit a sudden wilting, shriveling, and blackening of shoots, flowers, and fruit, giving them the telltale “scorched” look. It’s usually seen first on the plants blossoms and stems, turning them brown or black (dependent on the type of plant) and possibly distorting their form. Infected spurs and twigs display a darker, water-soaked appearance; they turn brown to black, then wilt and die. A watery, light tan ooze can exude from branches, twigs, or trunk cankers, leaving dark streaks on branches or trunks. Pink to orange-red streaks may be found underneath the bark in newly infected wood. The disease can spread from the point of entry (blooms, stems and branches, limbs, trunk, or roots) and may severely disfigure or kill individual limbs or entire susceptible varieties.
Mild temperatures (65 – 85°F) with some intermittent rain provide perfect conditions for the disease to develop. As trees resume growth in the spring, the bacteria become active. It’s spread by insects – aphids, flies, leafhoppers, and honeybees, pruning tools, wind and splashing rains. As long as the warm, wet conditions exist, the bacterium can continue to spread and infect new sites
The most effective means of managing the disease is to plant varieties that are not susceptible. Keep the plant vigorous and healthy through good cultural care. Minimize excess nitrogen fertilizer and heavy pruning, and if possible, don’t irrigate during the blooming season.
Watch plants throughout the year and promptly remove and destroy any portions that appear infected. Prune out diseased branches, cutting at least 8 to 12 inches away from the visible injury or canker, or until you see healthy tissue. The wood in an infected trunk or major limb may be saved by scraping off the bark down to the cambium layers. Removing cankers is best done during the dormant season (to reduce stimulating new growth) or after the weather turns hot and dry. Disinfect any tools, between each cut, to prevent spreading the pathogen.