Fireblight

This pathogen impacts the Rosacea family of ornamental trees and shrubs. While it is not native to the US it was first reported in New York in the 1700’s and is prevelent across the United States. Fireblight is most common on apple, crabapple, pear, cotoneaster, quince, serviceberry and many other trees and shrubs. Infection by the pathogen typically occurs in the spring by infecting the flowers and the diesease spread into the shoot and the leaves of the impacted branch. The infected leaves and shoots turn dark brown or black and the shoot tip starts to curl downward into a characteristic “shepherds crook” as seen in the photo to the right. The disease can also cause cankers on the trunk and larger branches. The bark on the cankered stem is dark, may be sunken or cracked and when the disease is active there may be a bacterial ooze emitting from the area. This disease is most severe during moderately warm temperatures ranging from 70-81 degrees with rainfall. Bacteria are spread by wind, rain and insects that spread the pathogen from blooming flowers. The bacteria can also colonize open wounds caused by wind or storm damage, pruning or other wounding activities. If not treated, fireblight can kill an entire tree over a period of time. While there are some treatments available for fireblight, the best control is to prune any infected branches out 12 to 18” below any visible symptoms. Conduct the pruning during dry weather and disinfect your pruners in between each cut using bleach or rubbing alcohol. If a tree has a history of fireblight you can apply copper products prior to bud break in the spring to prevent the inoculation of the flowers. Other treatments must be applied prior to any infection of fireblight.

Have questions? Contact our office where our Horticulture Extension Agent will assist you with questions.

Phone: (316) 321-9660

Email: callae@ksu.edu