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nafex - Re: [NAFEX] Fire blight on dwarf apple espalier

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  • From: <dmnorton@royaloakfarmorchard.com>
  • To: "North American Fruit Explorers" <nafex@lists.ibiblio.org>
  • Subject: Re: [NAFEX] Fire blight on dwarf apple espalier
  • Date: Thu, 31 May 2007 08:36:36 -0500

Betsy,

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
http://www.royaloakfarmorchard.com
http://www.theorchardkeeper.blogspot.com
http://www.revivalhymn.com
----- Original Message ----- From: <Hilborn.E@epamail.epa.gov>
To: <dmnorton@royaloakfarmorchard.com>; "North American Fruit Explorers" <nafex@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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