Anyone know what this is on Rhubarb leaves?

[JohnD]

If it's a fungal infection, a systemic fungicide will, at least, slow its spread.

It it worse on the top of the leaf, or the underside?

 

[Kaymo]

If it's a fungal infection, a systemic fungicide will, at least, slow its spread.

It it worse on the top of the leaf, or the underside?

Looks similar, maybe a bit worse on the top.

 

[Kaymo]

Thanks for all the replies folks.

I'm not going to spray anything on it. I would have to go out and buy something and if I was going to do that I would be as well to just buy a new plant and put it in another part of the garden.

I will try feeding it as I need to feed a few other plants in the same part of the garden this year, and maybe put down some mulch. It already seems to be getting worse since my OP, so I am not holding out too much hope for it!