found this link online when I googled pea moth - makes sense to me although I didn't suffer last year, I'm glad to say.
http://www.gardenaction.co.uk/techniques/pests/pea-moth.htm

I'd cover the plants with fleece, or better the very fine netting you can now buy. It's a lot of fiddle but worth the effort when you can eat delicious sweet peas that aren't full of maggots. You can grow a lot of peas in a very small area with the latest dwarf varieties, so doesn't cost that much to create a protected area.
I must admit that we grow an early crop in the polytunnel just to avoid this nasty pest as we can harvest them before the tomatoes and peppers go in.
Don't use sprays, they harm other insects and who wants to eat peas which are contaminated with nasty chemicals.

hi,thanks every one