I mentioned I'd write something on manually removing pests from the garden. I do this regularly for snails and slugs, although they seem to have become quite rare in this late summer season.
It seems to be cabbage moths that are the problem.
(It being early March 2014 when this was typed; after a year, they are still around, but the garden is so abundant they dont have much of a chance).
I have problems seeing the cabbage moths on the leaves, because they are almost identical in colour. So here are some ways I am experimenting with to find them so as to kill them.
First identify vulnerable plants being eaten. Some things like chillis, curcurbits, faux-spinach, solanums, and some mustards etc just dont get touched at all. Brassicas are the most vulnerable, and of those, toscana kale.
(A nocturnal spider web)
The easiest is to brush off the undersides of leaves to get the little yelllowish eggs, a plant or two a day. At night, put a small torch on the other side of your plant-leaves (of the vulnerable species) and look at the light through the leaves - a caterpillar (if more than 0.5mm long) will be immediately obvious on either side of the leaf. Then you can quickly see them. See photos of how this looks, forgiving my poor photography skills.
This sort of works, but is time consuming to get the angles of the torch right. So I tried another idea - using a UV torch light on (not under) the plants. This sort-of-works, for plant faces, but it takes the eyes some time to adjust to see things and see insects against the background.