Diseased seedlings?

[Giles]

I might be lumping together 2 unconnected problems here, but I would be grateful for your thoughts!
I've grown some Daphnes from seed, and have bought in 'a few' plants.
The seed has come from a variety of sources both commercial and via exchanges.
PART 1
I'll start with the seed:
I've some helathy looking D.koreana seedlings (Chiltern Seeds)
I've D.retusa from Piatek, which look a bit distorted.
I've D.longilobata from SRGC seed exchange- with slight streaking.

[Giles]

PART 2
In another greenhouse, some of the leaves on a D.genkwa have similar streaking. This appeared suddenly over the course of 2 days, about a month after
the seeds had germinated. Only some leaves have it. The leaf shape difference you see is due to the leaves being of different ages. Only the new leaves
on some of the shoots have been affected.

[Giles]

Apart from the time of sowing the seeds have not been handled in anyway. And as I stated they are in a different greenhouse from the more mature plants, and I have had no insect problems in either greenhouse. The Daphne genkwa I've had for about 7 months, and looked fine up 'til about a week ago.
I'm puzzled, because, although virus can be transmitted by seed and pollen it seems odd that seed from different sources should be similarly affected,
and even if it was, how it could be transmitted. I spoke with the man who supplied the D.genkwa, and his stock plants remain healthy, and mine was fine
until recently.
I don't know if I'm worrying un-necessarily, the plants are being quarantined until I'm sure that the call of the dustbin is inevitable.

[Paul T]

Giles,

The Dodgy genkwa reminds me a lot of mite damage in the early stages, even though you've said you have no insect problems.  A lot of normal insecticides don't kill mites.

Hopefully it is just an environmental problem like change in weather or something, but can't help more than that from over here.

[Giles]

Thanks Paul for that.
I sprayed with both an appropriate insect/acaricide and fungicide, and it is sitting in my outside loo, until I'm clear in my mind what's going on.
I half-hoped that subsequent new growth may come through looking healthy.

[Paul T]

Is there any signs of fine webbing on the leaf undersurface?  That minuscule webbing is another sign of the mites, but I don't think that all mites actually produce it.

[Giles]

No.
I sprayed them as a cover-all measure last week when I spotted the problem and moved them out of the greenhouse.(Without thinking of anything
in particular as the cause).
After your comment I had a good look at them under a low power microscope, but couldn't see anything at all.
I took cuttings from non affected shoots, and took a few root cuttings too, and I guess it's  now a case of wait and see.

[Paul T]

Glad to hear it Giles.  Hopefully it IS just environmental.

Maybe someone else has some ideas?

[Diane Clement]

I agree it looks like mite damage - have you looked on the underside of the leaves with microscope, Giles?  I had a problem with a batch of Cyclamen purpurascens a couple of years ago, I sent a leaf to Wisley for diagnosis and it was Bryobia sp mite.  I was advised to use Provado Ultimate Bug killer or something containing Bifenthrin.  The spray needs to be applied top and bottom of the leaves.  It took a couple of years of spraying to completely clear it.

[Giles]

All of this is very encouraging.
Yes I looked on both sides of the leaf surface - but had sprayed earlier, so guess the little blighters could have dropped off.
The parent plant continues to grow well, and the cuttings I took look fine too.
I'll spray regularly and keep you informed!

[Giles]

The Daphne genkwa is showing signs of improvement already - it is growing very rapidly at the moment (about 3 inches a week).
On the left, the older dodgy leaf, on the right, one of the new leaves produced this week.
I guess it will take longer to see what the seedlings are going to do, as they are growing alot slower.