North American Fruit Explorers mailing list at ibiblio

[Michael Dossett <phainopepla@yahoo.com>]

I'm having problems with my email so apologies if a partial message just got 
sent...

"Winterkill" is a problem with black raspberries wherever they are grown.  
There are three main theories about what causes it:

1. Cold winter temperatures and lack of cold hardiness
2. Variable winter temperatures
3. Diseases

Here in Oregon, for many years people chalked it up to 1 and 2 which didn't 
make a whole lot of sense because it doesn't get particularly cold here and 
growers seem to not have much problem until the 2nd year a field is in and 
then it seems to get worse every year after that.  Commercial black raspberry 
fields here only last about 3 seasons (4 if you're lucky) before the plants 
become so unproductive that growers rip them out and replace them.  Currently 
our working theory is that if cold temperatures are not the problem (which 
they may be in some parts of the country) then it is probably disease.  
Anthracnose, Verticillium, and different viruses can all cause this.  The new 
canes coming out in the spring seem to be healthy and vigorous and then they 
invariable die the next winter.  Fortunately we've seen some promising new 
germplasm in our breeding program that we hope will extend the life of 
plantings here, but that is a few years out.

I wouldn't be surprised if your plants might be diseased but it is entirely 
possible that water could be an issue, though it would make more sense if it 
was correlated to water conditions last summer and fall stressing the plants 
going into the winter.  I'd be curious to hear if you have the same problem 
next year.  If you do, it might be time to replace your plants and get new 
ones.

For a little more information on the problem here in Oregon and what we're 
currently working on check out the following articles: 

http://www.ars.usda.gov/is/AR/archive/jun06/berry0606.htm
http://www.ars.usda.gov/is/AR/archive/jan08/raspberry0108.htm

In some of our wild populations, reistance to the winterkill problem seems to 
sometimes be independant of whether or not plants are aphid resistant so 
there are other pieces to this complex puzzle still left to be uncovered.

Michael

Michael Dossett
Corvallis, Oregon
www.Mdossettphoto.com
phainopepla@yahoo.com


--- On Fri, 5/22/09, William C. Garthright <billg@inebraska.com> wrote:

> From: William C. Garthright <billg@inebraska.com>
> Subject: [NAFEX] Raspberry winter kill
> To: "NAFEX List" <nafex@lists.ibiblio.org>
> Date: Friday, May 22, 2009, 8:44 AM
> Most of my black raspberry canes died
> over the past winter, or at least 
> the tops of them did. The roots are all fine, and many of
> the canes 
> sprouted out from the bottom two feet, or so, but only a
> very few leafed 
> out all the way. I've been growing them for close to ten
> years, I think, 
> and this has never happened before. This will be easily the
> worst year 
> I've ever had (although, admittedly, last year was one of
> the best).
> 
> I asked the county extension office if other people here
> were 
> experiencing winter-kill in their raspberries, but they
> didn't know of 
> any. They just said they'd heard of "some" winter-kill of
> other plants 
> (which, I suspect, is pretty much what they'd say every
> year). Well, 
> they've never seemed to know much about fruit, anyway.
> 
> But I was wondering...  One difference this year is
> how dry it's been, 
> even for Nebraska. We've only received 2.72 inches of
> precipitation YTD, 
> which is six inches below normal. I usually spend all
> summer watering 
> like crazy, but I don't normally worry about it in the
> spring (since I'm 
> always exceptionally busy then, anyway), unless I've just
> planted 
> something. So I'm wondering if that's why the old canes
> died. Do you 
> think it might just have been too dry for them? The roots
> are still 
> sprouting out new canes like crazy, though.
> 
> I can't think of any other possible reason for this. It
> didn't get 
> exceptionally cold over the winter (down to -12 F. once,
> which is close 
> enough to normal). The temperature dropped to 23 degrees F.
> in April, 
> when they were just starting to leaf out, but that's a lot
> better than 
> some years, and the cold really didn't seem to bother any
> canes that 
> were still alive. I can't see any insect problems (I've
> never seen any 
> evidence of borers), and I've never had disease problems
> (the canes have 
> always been covered with spots that I suspect is
> anthracnose, but it's 
> never seemed to make any difference).
> 
> Just thought I'd see what people here thought. After all, I
> can't learn 
> from my mistakes if I don't know what they were. :-)
> 
> Bill
> Lincoln, NE (zone 5)
> 
> -- 
>  From the perspective of my hunter-gatherer forebears in
> the Pleistocene 
> Era, everything in the room I write in - the ceramic cup
> and the 
> carpentered chair no less than the electric light and the
> computer - was 
> as imaginary, as unreal, as fantastic as Narnia or
> Hogwarts. - Alison 
> Gopnik
> 
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