61005thumbBunches of blackened leaves hanging from blackened stems in otherwise healthy pear trees really are as serious as they look. They probably appeared as new growth was developing in spring, and are still as dead now as they were then. As surrounding foliage colors and falls, the blackened foliage will remain until it gets knocked out by rain and wind in winter, or until it gets pruned out.

Because these dead bits seem to have been scorched by fire, the bacterial infection that causes them is known as ‘fireblight’. Pear, flowering pear and evergreen pear are most susceptible to it. Apple, flowering crabapple, quince, flowering quince, hawthorn, loquat, cotoneaster, pyracantha and photinia are also very susceptible. Some cultivars are more resistant to fireblight than others. Few other members of the ‘rose family’ are rarely infected.

At the base of each dead bit (or toward the supporting limb from dead bits that do not stand upright) is a lesion where the bacteria that cause fireblight infected the stem. These infections not only obstruct vascular activity and kill the distal (outward) portion of the infected stems, but they also spread proximally (inward) to more important limbs, branch unions and even main trunks and roots.

Fireblight is transmitted mostly by bees, and also by other insects, birds, rain and wind, while trees are blooming in spring. It most often infects through flowers, and can also infect where infected debris, particularly falling flower parts, get caught in branch unions. If it infects root suckers, it can infect the roots right away, and kill an entire tree. Root suckers should be pruned away anyway.

There is no remedy for fireblight. Because it is very contagious, all infection should be pruned out. Because infection extends inward from obvious lesions, infected stems should be pruned back at least a foot and a half below (inward from) obvious infection. Sadly, this often disfigures infected trees, sometimes severely. Pruning scraps should be removed from around susceptible trees.

Some say that fireblight should be pruned out in summer. Others say that winter is best. Really though, the only bad time is spring, while weather is warm but still damp, and the trees that are so susceptible to fireblight are active and blooming. The reason for pruning it out in winter is that the disease is inactive while cold. However, it does not get cold enough here to slow it down much.

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4 thoughts on “Fireblight Kills Pears And Apples

  1. Informative post, Tony. There are a few apple and pear growers here that have suffered from fireblight. I don’t think it is as common in the northeast as in some other warmer climates, although your article did inspire me to look up some more info. The lower New England states are infected with outbreaks of this bacteria a bit more than us here in the north. I found this article to be interesting…https://www.ct.gov/caes/lib/caes/documents/publications/fact_sheets/plant_pathology_and_ecology/fire_blight.pdf
    As our weather warms here and we experience more humid conditions, many blights and pathogens are becoming more common.

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    1. Fireblight was a horrible disease that I heard about when I was a kid, but never actually saw. It made a resurgence in the 1980s, although I do not remember it much. I did not see much of it for a long time, and then it made another resurgence in the past few years. It seems to come and go in phases like that. I am nor sure how accurate that is, but that is my observation.

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  2. I noticed this on our pear trees a couple of years ago, and I pruned back the branches affected. I haven’t noticed any recurrences, but the pruning did make the trees look lopsided. Alas, even the disfigured live here and the young trees finally produced a few fruits this year – which amazingly, the squirrel and deer did not get to before I did!

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