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Re: rododendran's (carnt spell)

Lara,

Unfortunately, Rhododendrons are subject to a number of fungal and other
diseases.  What you are describing could be lesions caused by Phomopisis
fungus.  This will cause die back of the leaves and stems and the lesions
have a gray center with browning on the outside, more or less circular in
form, starting at the leaf edge.  

It could also be Leaf blight or dieback caused by Botryosphaeria dothidea,
but if this is the culprit, you should also see some indication of the
infection in the stems, which can turn black or just have many little spots
or depressions where the bark lesions are occurring.

It could also be any number of other fungal problems.  

If all the leaves on a particular branch are affected, the only thing to do
is remove the branch.  With these fungal diseases, it is important to
sterilize your cutters between cuts by dipping them in chlorox or alcohol. 
Also, clean up any fallen, diseased leaves and dispose of them in the trash
-- not the compost heap.

I have no verification that using a fungicide would help stop the disease
progress, but it probably wouldn't hurt.  Follow directions for application
that come with the product you choose.

Most of the time, these diseases attack Rhodies that are already vulnerable
from any number of causes, such as winter injury, pruning cuts, soil
getting too dry, soil not draining properly, lack of air circulation, too
much wind and other growing conditions that they aren't happy about. 

Depending on the age of your plant and the extent of the damage, making
certain that you have them sited properly and planted in the right kind of
soil (highly organic, fast draining, continually moist) and light (light
shade -- dappled shade -- morning sun) is the best cure for the problem. 
Rhodies are easy to grow providing you give them exactly the kinds of
conditions they want.  If you don't, they sure let you know by getting sick
and dying on you.

Good luck with your plant!

Marge Talt, zone 7 Maryland
mtalt@clark.net
Editor:  Gardening in Shade
http://www.suite101.com/frontpage/frontpage.cfm?topicID=222
Gardening Topic Index for Suite101:
http://www.suite101.com/userfiles/79/gardening.html


----------
> From: Craig & Lara Hawkes <networks@clear.net.nz>
> To: perennials@mallorn.com
> Subject: rododendran's (carnt spell)
> Date: Thursday, December 12, 1996 12:40 AM
> 
> Can anybody help me with my lovely red rodo's
> They seem to have a disease as follows:
> - browning off from the outside of the leaf into the
> middle of the stem in blotches
> - slivery white mouldy looking stuff then comes onto
> the brown die back
> - top leaves of the plant stand turgid but underneath
> growth hanging down looking very sick (these are 
> afflicked ones but not the top ones)
> 
> Hope some one can help as dont want to lose them
> Thanks lara
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