[NAFEX] Fire blight on dwarf apple espalier

dmnorton at royaloakfarmorchard.com dmnorton at royaloakfarmorchard.com
Thu May 31 09:36:36 EDT 2007


The general thinking among the major university plant pathologists is that 
pruning out the blighted shoots and burning them is the preferred attack for 
shoot blight with regularly timed sprays.  In Michigan in 2000 there was a 
statewide shoot blight epidemic.  As a result some great research was done 
and the info can be found at http://web1.msue.msu.edu/vanburen/fblinks.htm. 
Mark Longstroth compiled most of the data and he also refers to Alan Biggs 
from West Virginia University and Timothy Smith from Wenatchee in Washington 
State who developed the Cougar Blight predictive model that we use here at 
Royal Oak Farm.  Longstrith gives many examples of how orchard keepers 
approached the epidemic with varying results.  If you read through his 
reports, you should get a good idea of how to handle your specific 
situation.  Biggs and Smith have developed the best management programs I 
have found.

Blight typically starts with the blooms, spreads to the shoots, then to the 
trunk and finally to the rootstock.    I have not seen blight in rootstock 
without at least one shoot being infected first.  You might want to take a 
sample from one of your pear tree's rootstock and have it tested before 
removing the pear trees to make sure it is blight.  If the foliage is 
healthy, it may not be blight.  NC State has a good plant clinic  and  the 
information you need to submit a sample is at 
http://www.ces.ncsu.edu/depts/ent/clinic/.  I just removed 5 two year old 
Honeycrisp trees yesterday with rootstock blight (Bud 9 ), but each had one 
shoot that was blighted with a larege canker at the stem/trunk crotch and it 
was the last shoot before the rootstock.  All six trees were beside each 
other in the same east/west row.  Each of the trees to the east and west of 
the blighted trees were very healthy.

NC State has a good plant clinic  and  the information you need to submit a 
sample is at http://www.ces.ncsu.edu/depts/ent/clinic/.  Hope this helps!

Dennis Norton
Royal Oak Farm Orchard
----- Original Message ----- 
From: <Hilborn.E at epamail.epa.gov>
To: <dmnorton at royaloakfarmorchard.com>; "North American Fruit Explorers" 
<nafex at lists.ibiblio.org>
Sent: Wednesday, May 30, 2007 8:36 AM
Subject: Re: [NAFEX] Fire blight on dwarf apple espalier

> Thanks to Doug, Dennis and Jim for the quick response.
> I have been examining all of the trees daily and removing affected
> shoots (but probably not cutting enough!). I sanitize my pruners with
> high concentration isopropyl alcohol between cuts. I remove and throw
> away (in the trash) all cuttings and dropped leaves.  I have good weed
> control around the trees.
> I have never seen the bacterial ooze, but just the shepherd's crook
> appearance on the new growth (shoot blight).  My apples are from Lee
> Calhoun and all (I believe) are on M.9 rootstock.
> Something I have observed but did not know what to make of it is that
> all of my dwarf pears (blight resistant varieties from Stark Bros) have
> what I believe to be signs of blight on the rootstock up to the graft.
> Now, I do not know for sure what they use, but my understanding is that
> quince is typically used to dwarf pears. I don't know of any blight free
> quince.  My pears look great in general. The foliage is healthy, so I am
> hesitant to remove them upon a suspicion....
> I guess my plan is to spray all immediately, remove the Am. Golden
> Russet.  If I can figure out if I have trunk or rootstock blight can I
> keep things in check with regular sprays here in the humid south, or am
> I better off removing all affected plants?
> Thanks again for all of the help!
> Betsy  Hilborn
> NC 7a

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