Any idea what these yellow dots on my cucumber leaves?

[WeetabixLorry]

I bought these starter plants from the garden centre a few days ago as my own ones didn't germinate. I haven't planted them outside yet but I've just noticed these yellow dots on the larger leaves. Any idea of the cause?

It looks like damage rather than virus/disease, I'd say. If they're in a greenhouse, could it be damage from water splash on the leaves when the sun is strong? Assume you've checked for aphids etc?

I've got them in a sunny window. Been spraying plants next to them, could it be the water spray making it burn in the sun?

Thanks!

I am not a cucumber expert! But at a guess, from what you have said about spraying near them, it could be the onset of powdery mildew. Keep them watered as drought might be making them more vulnerable, space them out a bit, and maybe keep the air humidity down, i.e. don't spray.

The other possibility is something like pseudomonas syringae - fortunately, this is also helped on by lack of air circulation and humidity, so the same set of precautions may help.