North American Fruit Explorers mailing list at ibiblio

["Dennis Norton" <dmnorton@royaloakfarmorchard.com>]

Nathan,

 

The leaf in the photo is probably apple scab and from the description you gave of the weather, the temps were right for an infection period during the 90+ temps over Memorial Day.  Our scab software models here at Royal Oak Farm also showed an infection period for the same time, which is our third infection period in the last 2 weeks.  Nova or Captan is the necessary spray, but the timing is critical.  If you only have a few trees, Bonide Fruit Tree Spray contains Captan (needs to be sprayed within 72 hours of an infection period to really work), or go to http://www.planetnatural.com/site/xdpy/kb/apple-scab.html.  Refer to http://www.extension.iastate.edu/Publications/PM1282.pdf for the use of any sprays.  Hope this helps

 

Dennis Norton
Royal Oak Farm Orchard
http://www.royaloakfarmorchard.com
http://www.theorchardkeeper.blogspot.com

----- Original Message -----

From: Nathan Torgerson

To: North American Fruit Explorers

Sent: Tuesday, May 30, 2006 10:25 PM

Subject: [NAFEX] Necrotic leaf blotch?

Looking at my Zestar tree, I noticed yellowing leaves with brown spots on 5% of the tree. This took place in about 24 hours. 

Picture: http://www.nafex.org/uploads/is%20this%20necrotic%20leaf%20blotch%20on%20zestar%20apple.jpg 55K...next time I'll use underscores to eliminate the "%20" between each word...sorry about that.

 

It appears to fit the description of nectrotic leaf blotch, as the Twin Cities had one cool overcast week in the 60's followed by 3 hot and humid days (90+ degrees) over the Memorial Day Weekend. I'm not sure if Zestar is a Golden Delicious relative (Official cross is State Fair x MN 1691), which seems to be a prereq for this type of leaf blotch .  Anyone else seen this on Zestars?

 

I'm tempted to just leave the tree alone...I have never sprayed my trees for anything and really don't want to start if possible.  Has anyone dealt with this problem before? Will I lose my crop/tree if I ignore it?

 

Thanks,

Nate Torgerson

Andover, MN zone 4a

 

Description courtesy of Tennessee Extension services (there is also a picture on the site):

http://web.utk.edu/~extepp/fpn/fpn061504.htm

 

Necrotic leaf blotch is actually not a disease, but a physiological disorder. It occurs on Golden Delicious and its sports. The affliction often occurs in waves during the summer. It tends to be more severe when hot, sunny weather follows several days of mild, cloudy weather. Large, irregular-shaped, necrotic (brown) spots appear suddenly on green leaves. Most affected leaves soon turn yellow and fall from the tree. Defoliation can be significant. Although necrotic leaf blotch is not caused by a fungus, severity is decreased by a regular fungicide program.

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