Nathan,
Copper tends to burn up leaves in summer(higher
temps) as well as russet the fruit. Since we have over 10,000
trees, bagging is not a practice that would be practical for us. Bagging
is OK for some things, but when it comes to the diseases, it is of little
practical use. Since there are more organic approved sprays available
today, I would try an organic approach to diseases rather than
bagging.
----- Original Message -----
Sent: Thursday, June 01, 2006 12:01
PM
Subject: [NAFEX] Spraying for apple scab
with bagged apples
Dennis,
I have no experience with copper sprays, but from the little that
I've read, copper applications aren't used after silver tip because it causes
the fruit to russet if it's done later. I was guessing the russeting is
caused because the copper is applied on the apples, but maybe that's a bad
assumption, Do you know if there other reasons not to use
copper applications throughout the summer?
When trees are being sprayed that have the apples bagged
in plastic, the available use of certain sprays may increase since the spray
won't touch the fruit. (Or maybe when you spray before bagging, you need to be
careful because the chemicals will stay inside the bag all season). Since
bagging is fairly new, I haven't seen any discussion on how it might impact
the use of some sprays. Right now I am trying to stay with organic
measures on an as-needed basis to prevent major desease damage to the tree,
assuming that the fruit will be fine in the bags.
Nate T.
Dennis Norton <dmnorton@royaloakfarmorchard.com>
wrote:
Nathan,
----- Original Message -----
Sent: Thursday, June 01, 2006 12:53
AM
Subject: Re: [NAFEX] Necrotic leaf
blotch? - now apple scab
Dennis,
I agree with your assessment...just typical apple
scab, nothing as unconventional as Necrotic leaf blotch. I didn't
know that scab could cause yellowing of the leaves, but now I
know.
All the apples on the tree were bagged in plastic
one week before the scab symptoms appeared, so it will be a good test to
see if the bags successfully stopped the apples from getting
damaged.
I am trying to stay organic on my trees, so I'll
try micronized sulfur for control. I guess I could use copper as well,
since I would guess the bagging should prevent the russeting that can
occur with the application of copper sulfate.
Thanks for your help!
Nate
Dennis Norton
<dmnorton@royaloakfarmorchard.com> wrote:
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
----- Original Message -----
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.
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):
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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