Fire Blight of Ornamental Pears

EPLP-029 4/17

Sheila McBride, Extension Program Specialist David Appel, Professor, Plant Pathology and Microbiology*

Fireblight causes vascular wilt in many varieties of • also spreads by rain, which splashes onto the bacte- pome trees (apples, pears, and ornamental pears) and rial ooze and causes new infections; and members of the Rosaceae family (a wide range of trees, • infects new, tender, succulent twigs and leaves. shrubs, herbs, and ornamental plants such as roses, straw- berries, figs, and mulberries). With vascular wilt diseases, Control pathogens block the water-carrying (vascular) system • During winter dormancy, use sanitation pruning to of the plant, causing the leaves, stems, and branches to remove infected wood: wither, weaken, and die. – Cut an infected branch 4 to 6 inches below the One of the most destructive diseases of commercial visible injury or canker. apples and pears, fire blight is also a serious disease of the popular ornamental Bradford pears used in many Texas landscapes (Fig. 1). Other common Texas woody orna- mentals affected by fire blight are loquat, cotoneaster, and pyracantha. Symptoms • Infected flowers become water-soaked (translucent and wilted), shrivel, and turn brown. • Leaves progressively turn brown, develop black blotches, curl, and eventually shrivel. • Twigs wilt from the tip downward, turning black and curling in a “shepherd’s crook,” giving them a burnt appearance (Fig. 2). • Branches develop dark, sunken cankers that enlarge and girdle the branches. Eventually, the branch dies (Fig. 3). Cause and Environmental Factors The bacterium, Erwinia amylovora, causes fire blight. The pathogen • over-winters in cankers, budscars, and branches; • forms an ooze that attracts insects, including bees, that then spread the bacteria via the nectarthodes (openings at the base of flowers);

* Texas A&M AgriLife Extension Service, The Texas A&M University Figure 1. Typical signs of fire blight on a Bradford pear tree.Source: System Sheila McBride

1 – To avoid spreading bacteria during pruning, • Reduce new infections by spraying an antibiotic such sanitize the pruning tool before each cut, using as streptomycin sulfate (Ferti-lome® Fire Blight Spray) a 10-percent bleach solution (one part bleach to on flowers or shoots before the bacteria infect them. nine parts water). A copper sulfate fungicide (Bonide® Copper Fungi- – To prevent rust, dry and oil tools after using cide) is also an option when applied several times them. while the blossoms are open. (Neither option will • Reduce excessive succulence by avoiding extreme eliminate all new infections or those already existing fertilization and watering. in the wood.) • Plant moderately resistant varieties. Refer to product labels for proper rates and use.

Figure 2. Shepherd’s crook symptom of fire blight in young twigs. Figure 3. Burnt appearance of Bradford pear twigs. Source: Sheila Source: Sheila McBride McBride

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