Sounds like cabbage loopers to me... they tore up my broccoli this year.
They were my "sacrificial" plants, and the rest of the garden did fine.
Organic Gardening has this write up
on possible solutions
http://www.organicgardening.com/feat...-9-266,00.html

heres another link that may be of some help
http://www.ghorganics.com/page14.html

good luck
tim


"I & H Prees" wrote in message
k.net...
Pardon if this has been asked before but I'm a newbie (both to vegetable
gardening and this newsgroup). I planted brussel sprouts for the first
time
in my Massachusetts garden this year. The seedlings I started inside
didn't
transplant well nor did many of the seeds I sowed directly take hold in
the
garden. I only have about three plants growing. And now the leaves are
covered with holes and I'm finding inch-long smooth green worms on them.
They don't seem to be on any of my other vegetables or herbs. I try not to
use any pesticides on my small garden but I'd like to have my kids see at
least one impressive brussel sprout stalk grow to maturity...any
suggestions
for non-chemical/pesticide deterrents for these pests?
Also advice on getting brussel sprouts to grow in the first place

Thanks
-Holly