[Alice]

Can anybody - Mike or other insect expert - identify these eggs seen on an almond tree? Do I take action or leave to their own devices?

[Pia]

I am sorry to tell you that two weeks ago we visited our neighbour in Argolis and her two beautiful almond trees was a disaster. All over the trees were ribbed for foliage and there were hundreds of huge green larvae all over the trees. They have long hair! She had (despite of alwais not using chemicls) sprayed with some chemical 5 days before. they disappeared, but 3 days after spraying there were as many again. And eggs looking like yours.
I am sorry for the quality og my picture.
Hope the best for you and your almonds.

[MikeHardman]

How about...

Saturnia pyri, the giant peacock moth -
http://tpittaway.tripod.com/silk/s_pyr.htm
Scroll down that page and you'll see eggs and caterpillars.

Also http://en.wikipedia.org/wiki/Saturnia_pyri.

Mike

[Alice]

Thanks for your replies, Pia and Mike.
Mike, the eggs do look like those of Saturnia pyri but are on the stems, not the leaves.
I removed the ones I could see but have now discovered that the tree is covered in black scale insects, which seem to be farmed by ants. Do you think the white eggs (?) might be related to the scale insect?
Alisdair, I think this thread should now be moved to "Pests and Diseases".

[David Bracey]

I doubt that the eggs are associated with the scale.  I have never knowingly seen scale Eggs but I think they are microscopic. 

[Alice]

Thank you, David.
I have so far seen no caterpillars, having emerged from the eggs.
I am removing the scale insects by hand (fortunately it is not a big tree). They are really dark and stain my fingers. I will probably also spray with a soap solution.