[carlrmj]

I used debris netting to protect my brassicas last year and this year

Last year no damage at all by caterpillars

This year the cabbage whites got in through the eyelet gaps by folding their wings
 
They ruined my cabbages ,sprouts and kale(which they never touched last year,even when some wasn't netted)

It was a nightmare trying to pick off the caterpilars and keep on replacing the netting

[Kristen]

No, non-organic commercial growers have an arsenal of chemicals instead

And, in my case, that's a key reason for growing them(all veg in fact) rather than buying produce in the Supermarket

[Kristen]

This year the cabbage whites got in through the eyelet gaps by folding their wings

I hope the evolved types don't migrate here!

I have known of people showing up the eyelets.  Dunno how hard, or otherwise, that is though.

[goodtogrow]

Or strong tape over the eyelets?  And making sure where netting meets soil there's a perfect seal?

It's all a bit of faff, but while we're faffing we could lay weed membrane as well and plant through that, so there's no maintenance.  You could even water through the netting if you wanted to.

I think we must all value the crop when we can get it, so I hope the op will persevere.  By chewing the cud we seem to come up with solutions to any problem.  That, I think, is the power of this forum.

Best wishes

Tom

[bravemurphy]

You will never stop them completely I don't think because I caught some commando catterpilers crawling across the floor and going under the netting

[Gardener and Rabbit]

The only brassica we grow is kale (Starbor) because it recovers after the caterpillars have finished, and we get our crop then. 

Late September/early October I go over the plants, stripping-off all the eaten leaves and any caterpillars, and throw them away, to leave just the stalk and 2 or 3 of the very smallest new leaves at the top. I give the plants a bit of liquid feed at this stage to encourage them, and find they grow back quickly with nice undamaged leaves.

[RJR_38]

This year the cabbage whites got in through the eyelet gaps by folding their wings

I hope the evolved types don't migrate here!

I have known of people showing up the eyelets.  Dunno how hard, or otherwise, that is though.

I just get some thick twine/string and weave it through the eyelets all the way along. It is very easy to do even on my 6m long tunnels. I find this is a good compromise between sewing them up which is a faff when you don't have a machine and leaving them empty. Having the twine running through means the gap (although still slightly bigger than the netting holes) is much smaller and cuts down the risk hugely. I have only lost one cabbage to caterpillars and I think the eggs probably got laid on the day I opened the tunnel to weed and the whites were flying everywhere...

[gobs]

This year the cabbage whites got in through the eyelet gaps by folding their wings

I hope the evolved types don't migrate here!

You hope! Lol! Just like that they get in, I watched them, many a time. Wings flats, squeezing, no flying involved.

Indeed, they are evolving to cope, I have been thinking on many occasions.

And then, if nothing else, they start laying on chards and such...

[Kristen]

You hope! Lol! Just like that they get in, I watched them, many a time.

Well, like I said, not here, not yet. Been using debris netting for 6 years or so and not had a problem yet.  Plenty of cabbage whites flying around during the summer ...

... unless there are different types of debris netting, as someone else proposed earlier in the thread.