Could be lots of different things nibbling the leaves, personally I wouldn't worry too much about unless the leaves are being eaten completely. I'm sure you already know but you can't pull any stalks of rhubarb this year and only a few next.

it could also be hail stone damage. mine have been badly damaged this week.

Moongrower, why do you say we can't pull any stalks of rhubarb this year? It's not something I've heard of.

In order for the crown to establish during the first year after planting in needs all the nourishment from the leaves and stalks going back down into it, pull the stalks for eating and you are depriving the crown of this.

Thank you for the comments. I will keep an eye on it. Yes I know I can't pull it this year.

When I planted small beetroot plants last year I noticed small birds dive-bombing the plants and pecking off small bits of leaves. I covered them until they were bigger. Maybe the birds like young rhubarb leaves too!

It's unlikely to be birds, are you sure that last year they weren't pecking off insects?

Well, I suppose they could have been but it stopped when I covered the plants and then they grew bigger and once they were a decent size I was able to uncover them without anything happening to them from them on.

On another note I have bad slug damage to my hostas. I have tried everything. Are nematodes the way to go?

We see hostas as a way of keeping slugs off our other plants... they decimate them every year.

Ah, I see. It's only for the first year. Thank you for clarifying, Moongrower.

Yes and no Arbuthnot, even in the 2nd year you should rally only pull a few stalks not crop the whole plant.

It doesn't really matter because ours on the allotment is a very well established clump. It's just that I didn't know about not pulling in the first year. You learn something every day, don't you:)