I read somewhere that cabbage white butterflies would not lay their eggs on leaves that had been watered with water that had had rhubarb leaves soaking in it for a few weeks. My question is, as rhubarb leaves are poisonous to humans, doesn't this action render the brassica plants dangerous to eat? Thanks for any advice.
I just net them.
But it has to be really fine net. Last year, the Bl**dy things wriggled their way through sa called 'butterfly netting', an did their worst. They often couldn't get out again!!!
This year i've had the plants under cloches made from old net curtains, which are fine, but we're now making larger ones and using very very fine insect netting 9expensive!!) from Harrod horticultural.
So fingers crossed.
as for spraying with rhubarb water - don't know.
Wash your leaves before you do anything else with them, and you'll get rid of any rhubarb liquor or anything else you've put on them, along with the caterpillar poo. I very much boubt whether you'd get enough oxalic acid that way to do you the slightest harm, as you're a great deal bigger than a butterfly!
http://cgi.ebay.co.uk/Insect-Fly-Bed-Canopy-Protection-Netting-Mosquito-Net-/270733323163?pt=UK_TravelTickets_Accessories_RL&hash=item3f08f6ab9b
What do you all think of something like this? I happen to have a roll of mosquito netting bought in a very insect-ridden Polish summer, and wondered what more might cost. It would be a very agile butterfly to squeeze through that.