Problem with rhododendron buds

[Maggi Young]

An old friend from Glasgow writes :
"...... I am writing to  report a problem which concerns me in order to alert members to watch for it.
 
 Some of my Rhododendrons have buds which look good during the Winter but prove to be blind or dead, possibly diseased.
 
 My solution so far has been removal of affected plants which is helping somewhat.    I cannot say which types are most susceptible but the Lapponicum subsection seems healthy as do the "Yak" hybrids.
 
Whatever, I would welcome comments and hope that other members are not greatly troubled.
 
Sincerely
 
 Brian Knights "

This is a problem which  has affected certain plants here in our Aberdeen garden from time to time - but never as a widespread "attack" being only on one or two plants.  I  haven't been aware of any being affected this year-  what do others think the problem might be?
I have never been sure if "bud blast", which is a fungal disease is really the cause?

[johnw]

Maggi - If it is true bud blast you should see tiny black bristles on the bud itself.  R. wardii itself and possibly its hybrids are said to be particulary prone to bud blast.  We had a bout of blown buds on wardii here for a couple of years but it was not classic bud blast bud summer drought inflicted.

johnw - plant sale weary....

[Maggi Young]

I haven't seen the fungal bristles here, John. Brian made no mention of bristles in his note.

Here the problems have been on R. tsariense and  sometimes on oreonastes.

[birck j c]

Here what it looks like
and the culprit  -  but havenot seen any connection


birck
copenhagen
z6

[Maggi Young]

From Brian Knights:

" Thanks Maggi I have no black bristles but the buds are brown inside and dry
 with no sign of mycelium.    It may be too early for fruiting bodies on the
 outside but I incline to your view - that it is not bud blast.
 
 Rh. calostrotum (or saluenense) shows the problem but is more resistant  and
 carries a fair amount of flower.   'Nancy Evans' has had troubles in the past
 but is flowering like billyo this year.     Perhaps the comment about
 drought may apply not withstanding the weather last Summer - a short dry
 spell at the wrong moment perhaps?
 
Best wishes

 Brian"

[Maggi Young]

Odd, isn't it? I must  have a good look to see what is happening this year with those which have previously been affected.
We have been delighted with how well some rhodos are flowering this year, though some are clearly taking a year of and only making growth buds.

Can't say I've ever seen the problem on calostrotum types. I haven't seen it on any of the named hybrid rhodos either.
We were expecting  a poor flowering season  this year after last summer - but  for the most part it has not been at all as we feared.

There is just such a lot we do not know or understand, isn't there?

[Roma]

My Rhododendron calostrotum 'Gigha' aborted most of its buds this year and the flowers which did open got frosted the next day.  I'm not sure if the developing buds got frosted as we have had very little frost recently but I suppose a light frost after a couple of weeks of night temperature well above freezing could do more damage than consistently low temperatures.

[johnw]

Rhodos in dry spots will sometimes abort pips or the entire bud during or after a dry summer here.   With the latter I presume when the autumn rains arrive they start to move and then get zapped by a good hard frost. 

The same events can spark a good flowering with the lepidotes if your lucky, one year the Lapponicas flowered in May, late June and again in the autumn.  What is truly amazing is that they managed to set buds and flower normally the following Spring.  I've also seen a rash of full flowering on deciduous azaleas the past two years - Golden Lights and Lemon Lights and for that reason I'd avoid them like the plague as no others have that habit which coukld be a tissue culture problem.

Jens have you seen this phenomenom?

johnw - tsariense in flower......