stopping caterpillars destroying purple sprouting broccoli

Best non chemical protection is envirofleece , but you may need more than one to cover them as they grow tall., you have been visited by cabbage white butterflies, look underneath the leaves and rub off any eggs and pick off caterpillars, they will sprout again if you leave them, long growth period.The butterflies also like nasturtium, next year plant under fleece and if you plant some nasturtium they will be attracted to those instead. A pond would encourage predators like frogs.

Thanks very much! I have noticed a few cabbage whites around.

I have found loads on my Broccolli this year and for the first time found them also on my nasturtiums.
Cabbage whites seem to be every where along with other butterflies. I thought these were all in decline?
It seems they are living in my garden.

This has been my first year at growing veg. I planted Cabbage, Broccolli and Coliflower . The cabbage were the first to go then the broc, now I've just noticed catapillars on my colis. Next year I'm going for a microfleece cage. Microfleese is very cheep, but watch the cats they love to tear it. I'll have to reinforce it with some netting.

you can get netting which is butterfly proof , i made a wooden cage and fixed the netting to this so there were no holes anywhere, seems to have worked...so far