holes in the Pak Choi

I'm not sure enviromesh would work, as I think they may already be in the soil?

Happy to be corrected if I'm wrong 

I had a row of mixed green, red and white pak choy growing on the allotment and the flea beetle was attacking the leaves. I covered them with fleece and the new leaves that grew after that did not get any holes. I would definately advise this, although it did keep the rain off to a degree and pak choy needs lots of water so you will need to water regularly, otherwise they may bolt early. Mine did, although the red pak choy didn't bolt.