On 02/08/2012 17:51, David in Normandy wrote:
Cabbage white butterflies have found my brassicas hidden amongst the
marigolds and they are heaving with caterpillars. Are there any natural
remedies other than wearing rubber gloves and squishing them all?

Pyrethrum or rotenone both natural and fairly deadly to caterpilars.
Nicotine is deadly to humans as well as pests (and a vector for TMV).

Unless you intend to sell it are Organic(TM) produce I'd be inclined to
use one of the specific short lived knock down pesticides that is OK for
use on produce. Don't leave it too long or you will be left with bare
ribs of brassicas and no leaves at all. Happened to me last year while I
was away - 1 week and came back to skeletal plants.

Amazingly the purple sprouting broccoli came back to crop eventually but
the rest did not.

--
Regards,
Martin Brown