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Past Articles Library | Plant Diseases & Control | Fire Blight

FIRE BLIGHT DESCRIPTION
(Erwinia amylovora)

Fire blight is a bacterial disease that causes a sudden wilting, shriveling, and blackening or browning of shoots, blossoms, and fruit. Infection first occurs during bloom. Infected blossoms appear water-soaked and turn brown or black. The infections may then spread through the blossom-bearing stem, turning it black, and into the spur or main branch to form a canker. Rapid infection of extensive portions of the plant gives it a "scorched by fire" appearance with dead leaves remaining attached to twigs. Branch tips curl, giving them a "shepherd's crook" appearance. Cankers can form on twigs and branches, which may die back.

LIFE CYCLE

Fire blight bacteria over-winter in cankers on twigs, branches, or trunks of host trees. In the spring when the weather is warm and moist, and trees start actively growing, bacteria multiply in diseased tissues and ooze from branch or twig surfaces in a light tan liquid. The bacteria can be transmitted to nearby flowers or succulent growth by splashing rain or insects, especially honeybees. Open wounds on trees are easily invaded by Fire Blight bacteria.

Ideal conditions for infections and spread are rainy or humid weather and warm temperatures. Once bacteria enter the flowers, they may cause only a localized infection and eventually die or move into twigs and branches. Once the bacteria is established, the distance it moves is in direct relationship to the rate of tree growth.

PLANTS MOST AFFECTED

A bacterial disease that damages only plants in the pome tribe of the rose family including apple, evergreen pear, hawthorn, loquat, pear, pyracantha, and toyon.

MEANS OF CONTROL

There are several control methods:

• Plant varieties that are less susceptible to fire blight
  
  
• When tree is dormant, spray with neem oil, copper sulfate or bordeaux mix
  
  
• Eliminate fire blight by pruning diseased branches back at least 6 inches (cm) into tissue that looks healthy and removing diseased wood. To prevent spreading pathogens on infected tools, dip your pruning shears or saw in a diluted bleach solution (mix 1 part bleach to 5 parts water) after every cut. When you are finished, thoroughly disinfectant your tools in the bleach solution for several minutes.