The spores produced by the tubular structures complete the cycle by infecting the juniper host, which, in Nebraska, is usually eastern redcedar. Other juniper species, such as Rocky Mountain juniper, are also susceptible. Fire Blight Figure 2. Fire blight is the oldest, most serious bacterial disease of crabapple, pear and apple trees. The disease is indigenous to North America and probably occurred on native American plants and then spread to susceptible cultivated apples, pears and woody ornamentals planted by early settlers.
Fire blight has a wide host range.
In Nebraska, hosts include apple, crabapple, pear, cotoneaster, hawthorn, firethorn and mountain ash. Infected blossoms wilt, shrivel and turn brown. Succulent shoots of new growth and water sprouts are also susceptible. The infection advances from twigs to older branches and limbs causing localized cankers, which appear sunken, dark and wrinkled. Cankers on large scaffold limbs and the trunk eventually become cracked or creviced.