[yvesans]

My Sago palm has suddenly developed a lot of yellowish spots on all the leaves, topside only, I have looked at most of the pests and it does not fit the description of scale infestation, seems more possible to be a mineral deficiency, I wonder if anyone has any experience of this?

[David Bracey]

Any pics?

[Alisdair]

Yes, a photo would help!
In our UK garden we have a king sago (Cycas revoluta) which most years has a sparse scattering of tiny yellow spots on at least a few of its leaves. Leaf spots are notoriously difficult to diagnose, and I have in the past assumed that ours - really not noticeable enough to worry about - were originally thrips puncture marks, as in the winter we have moved the potted plant into a cool greenhouse where other plants do get attacked by thrips. However, such spots can also be caused by cultural problems, or even spray damage. Prompted by your question I've just had a closer look at our plant and noticed that this year's scattering of tiny spots mostly seem to be on one side of the fronds, which would square up with a reaction to spray drift - even a fungal attack following just plain water spray.
Cyprus has had some dire storms this year, so I suppose another possibility for you to keep in mind is hail damage.

[John J]

Do your spots look anything like the ones in the photo?

[yvesans]

Thanks all, here is a photo I took this morning, all leaves are much the same now,

[yvesans]

Yes looks the same John

[John J]

I have no idea what they are caused by either but Alisdair's explanations sound plausible. They don't appear to be having an adverse effect on the plant's health so I'm not too worried about them at this stage.

[MikeHardman]

"The beginning stages of manganese deficiency are yellow-brown spots or streaks resembling a pathogenic disease"

That would be my first choice for an explanation.
But see also the other issues discussed in this paper -
http://cfextension.ifas.ufl.edu/documents/Sago.pdf