[Amilo]

This year I have no Brassica but noticed a cabbage white on the Nasturtium, on close inspection the little b...er had been laying eggs under the Nasturtium leaves

Would the larvae feed on Nasturtium?

[vanessa.xx]

Yes I used to have them in my back garden and they would be crawling but nothing seems to hold nasturtiums back

[bravemurphy]

They are great for taking the whites away from the brassicas I don't mind them laying on the nastursums.

[compostqueen]

I plant nasturtiums for that very purpose. Rather the flowers than your brassicas 

[Amilo]

This is good news, now I can have some brassica next year.

[pdblake]

I've put some in this year too but, while I've found caterpillars on the odd brassica, there's none on the nasturtiums

[seaside]

I have recently discovered one other way to attract the cabbage white away from the crop that matters is to let the odd older brassicas or two go to seed. The vibrant yellow flowers attract the butterflies for the nectar, and then they lazily lay their eggs on the those plants. My nasturtiums tend to grow too late to be effective... they are only just starting to flower and are quite small. I will be trying the duff cabbage thing next year  for the Summer crop with an the old kale and PSB. I have noticed in the past that old flowering kale has attracted mealy aphids as well.

[JayG]

I've never been in favour of types of companion planting which in effect set up a thriving breeding colony of the pest you are trying to control.

That's not to say that some companion planting doesn't work - Tagetes to repel whitefly; yes, alliums to confuse carrot fly; possibly (to some extent), and no doubt some others, but relying on a competitor target plant to solve your bug problem seems too risky to me, especially in the case of the cabbage white which can be so damaging if it doesn't work, or only partially works.

[seaside]

Interesting. If one was growing alone, than maybe I might have initially agreed with that, but given that virtually every utilised plot on our 120+ site grows brassicas and sports less than effective netting, I don't think the cabbage white is going anywhere soon in our neighbourhood.

Moreover, when the sacrificial lamb ( or should that be mutton  ) lures it's prey with the smell of food, I'm more liable to spot the eggs and caterpillars and deal with them because I won't have the fiff faff of removing netting which inhibits proper inspections to once a week. I'm thinking it will mean less, not more, cabbage whites. Many of nature's cures work this way. The only free cheese is in a mouse trap.

[JayG]

Since many of your fellow plot-holders seem to have accidentally set up their own breeding colonies of cabbage whites anyway, surely the easiest and safest course of action is to forget the nasturtiums and make sure your netting is 100% effective?

[seaside]

I was actually talking about the odd gone to seed brassica, not nasturtiums.
As for 100% effective netting ... do me a favour. We do have to get in there to weed, to feed and deal with various issues over a season. I don't know anyone who treats brassicas like carrots and carrot fly. Some people go for a massive walk-in brassica cage. Well, that isn't the easy option either, let alone it's oppressive nature and the need to move it every season.

I have used enviromesh this season, properly pegged down. I don't know what more I could have done, and the blighters still got in and affected a few plants, just like they do with stitched debris netting. The leaves only have to touch the sides on occasion and they're doing their thing through the net.  That mesh has in my opinion also been too hot for them in the last couple of weeks so I have now gone back to ordinary small netting that tends to allow better rain, light and temperature transmission. Will save the enviromesh for carrots.

So, I'm thinking a little companion planting of an old worn out brassica wearing her yellow earrings outside whatever netting I use is an excellent supplementary idea to try.

[compostqueen]

I love the nasturtium but it's not the only tool in the box   

[RichardA]

yes nasturtium decoys work but you still need 100% netting and make sure the brassicas never grow so far as to touch the netting as the little dears can lay through the netting. Keep it well above top and away from side  leaves.