You need to make a complete cage over them with either hoops or small canes, allowing for some growth over the next few months until the CW's disappear. I use netting which isn't that expensive and keeps from year to year, any gaps and the little monsters will get in.

Hi Lizziebee..... I have made a cage for mine from enviromesh....do you know when it will be safe to remove it?

Environmesh is on my list to buy in the winter months.

With tongue firmly in cheek, may I suggest that fighting nature can be a frustrating and expensive battle!
Try your local greengrocer - you know it makes sense.

P.S. Awaits indignant comments!

This also happened to me in my pollytunnel that was very expensive it came with a smaller tunnel with netting I now am left with just stalks I have sprayed now and was left with loads of green caterpillars on the soil will they grow back?