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identifying fire blight

Posted by Robbie Anderman 
identifying fire blight
May 07, 2015 03:57AM
I'm confused as to exactly how to identify fire blight on an apple tree. I thought it was by looking at the branch tips and seeing a shepherd's crook and black. On my Red Haralson, there is absolutely no shepherd's crook. Only black on a 4 inch thick branch that even has what looks like white sea shells growing out of it. Definitely a dead spot about a foot long... yet most of the branches beyond that point are still alive and budding out. I am tempted to cut the whole branch off, yet it's a big one. Is it fire blight? Or something else? What's the best route to pursue?

thanks so much,

Edited 1 time(s). Last edit at 05/07/2015 02:23PM by Michael Phillips.
Re: whey probiotics for fire blight
May 07, 2015 04:50AM
Without a picture it is very hard to tell. However, a very similar looking disease - nectria twig blight - is also known as coral spot because of the seashell looking fungal growths that infected tissue develops. I grew Haralson for many years commercially and don't ecall it being even the slightest bit susceptible to fireblight. However, because of how nectria twib blight infections can occur (at the base of poorly healed pruning wounds, winter damage, base of pedicels of harvested fruit -- in essence wounds), it wouldnt seem totally out of the question that it is in fact NTB and not FB. But without a picture.....I can't really tell. Nectria Twig Blight

Mike Biltonen, Know Your Roots
Zone 5b in New York
Re: whey probiotics for fire blight
May 12, 2016 09:51PM
well, they sure don't have those coral looking growths..... and now its on another tree, quite severely, two to three inch branches with only bits of surviving thriving buds.... dry black bark, some shrivelled
I will burn the cut off portions, asap.
Re: identifying fire blight
March 01, 2018 03:45AM
]This year we're looking over the results of the past year... and it seems quite discouraging...
At the same time, we're left wondering.... autumn was so warm and so long that leaves stayed on the Trees until suddenly the Cold descended BOOM!
So we have small branches still holding dead leaves... small branches that may have died from sudden cold... especially considering that we kept cutting branches when we saw signs on FB.... and thus spurred new growth.
Confusion reigns.....

this will be a challenging pruning season.....

Morninglory Farm
Zone 3b* in Ontario
Re: identifying fire blight
March 01, 2018 03:47PM
Three things, Robbie, to further deepen the confusion!.

We had that same cold hand descend in November, essentially "locking" leaves on late varieties where abscission was not as far along because of the warm fall. I am curious why that happens. Anyhow, I'm not getting the sense in pruning now that the buds for this year and the wood tissue in shoot tips died back as a result. Brown leaves are still on some of these trees (along with a handful of very soft, brown apples) though most leaves blew off through the course of the winter.

The maxim "everything is everywhere" applies to fire blight yet regardless conditions have to be right. High temps and moisture during bloom (and that month following) enable bacterium to be on the move anew. I saw no fire blight strikes here in northern New Hampshire this past season. You would be seeing sunken bark where vascular damage has occurred. Cut along the length of a small branch where cankering is obvious. Does healthy cambium transition to brown decay? Type in the words fire blight canker into Google Images and you will see tons of examples. Active cankers will be oozing as the weather truly warms, disseminating a first round of bacteria. (That's the justification for applying dormant copper, in order to throw "blue pianos" into bark crevices and bud scales to crush any waiting bacterium before it can strike later.) Trees are capable of compartmentalizing damaged zones, in which case the canker zone dries up and vascular infection goes no further. If the sunken section does not fully extend around the entire branch circumference, then yes, buds on some of the branch structure beyond could still show life.

Which brings us to black rot. The "mother of all cankers" that you described at the start of all this is very likely a stretch along a branch where black rot fungi (Botryosphaeria obtusa) claimed a damaged niche, be it a fire blight strike or nectria or an uncallused pruning cut or cold injury or sun damage or a hail strike. The resulting vector is dead wood. These cankers tend to grow more quickly along the length of the branch, compared to going around the branch. Fresh cankers have an orangish streaking aspect along with shriveled-looking bark, first adhering tightly to the wood but then seeming to peel and flake off. Several posts in this forum touch on the conundrum of black rot. This is definitely relevant to apples but not so sure to what extent it manifests on pears.

Lost Nation Orchard
Zone 4b in New Hampshire

Edited 1 time(s). Last edit at 03/01/2018 11:00PM by Michael Phillips.
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