North American Fruit Explorers mailing list at ibiblio

[<dmnorton@royaloakfarmorchard.com>]

Alan,

 

We have had fire blight infections in some form or another over the past two seasons.  We had no blossom blight either year.  it has either been shoot blight, stem blight, or root blight.  Last season we removed about 12 trees that had severe stem blight (if more than two scaffolds are blighted it is best to remove the tree from the orchard). If not dealt with, fire blight will keep coming back, and worse the following season.  Once the infection is in the orchard, it is very difficult to get rid of.  There is no cure for fire blight, but its spread can be limited. Prune cankers preferentially during the dormant season at a time when branches are dry. Prune out blighted branches as soon as you see them.  When removing diseased dormant branches, prune 6 to 8 inches below tissue showing visible symptoms. If pruning is required during the growing season, prune at least 12 inches below the diseased area.  Always, disinfect pruning tools by dipping them for at least 30 seconds in 10% bleach or alcohol after each cut (spray disinfectants that contain at least 70% alcohol can also be used). Burn or bury diseased branches. 

 

Along with our usual Strep spray with Regulaid at bloom, I will be using an Apogee program this season to manage shoot growth.  After terminal growth stops, fire blight cannot infect new shoots and blight cankers do not enlarge. 

 

I have a copy of Dave Rosenberger's "Fire Blight Management Program for Apples" from Cornell that I would be happy to e-mail to you if you would like.  (Or anyone else who would like a copy.)  I attended his clinic on fire blight a year ago at our Specialty Growers Conference.  He gave us a 7 Step program that has been trialed very thoroughly at the NY State Agricultural Experiment Station in Geneva (same place the Geneva rootstocks are from).  There is also a good article from three top pathologists at Michigan State, Cornell, and the USDA Experimental Station in Kearneysville, WV that is found at http://apsjournals.apsnet.org/doi/pdf/10.1094/PDIS.2003.87.7.756?cookieSet=1.  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: Alan Haigh

To: nafex@lists.ibiblio.org

Sent: Saturday, April 05, 2008 7:20 PM

Subject: [NAFEX] vectors for shoot blight

In the last two years I've been seeing quite a bit of "shoot blight" at a couple of sites I manage- that is fire blight that doesn't seem to start with an infection of the blossoms.  The only visible signs are blighted water sprouts, mostly in the interior of the trees.  In one site where it is apples that are infected there are a lot of cankers on big scaffolds that started from these infected water sprouts.  The trees are mostly Empire, Macoun and Northern Spy with the first two having most of the strikes.  The trees are on seedling rootstock and are about 20 years old.

 

When I asked the key Cornell commercial fruit-grower advisor about it he insisted (after a brief consultation with their pathologist) that the infections must have started on the blossoms then moved on to the water sprouts leaving no visible damage at the infections origin.  He was confident of this because there were no serious hail storms coinciding with damage and so bees must have been the vector.

 

I'm curious if others out there have seen similar infections where symptoms don't appear for about a month after pedal-fall and no damage is visible around fruiting shoots.  If so, did the blight keep coming back?  So far the damage isn't life threatening but I'm wondering where it's going.  I have so many orchards to manage so spread out that this is a very difficult disease for me to deal with.  I'm also seeking a second (third or fourth hopefully) on the diagnosis I received.