Horticultural oils and insecticidal soaps can be particularly effective at this stage if you get good coverage. Bt will have no effect whatsoever on sawflies. With snow on the ground here in Maine it's amazing to think that people are getting into gardening elsewhere.

Monterey Garden Insect Spray works great. Neem, insecticidal soaps, or other insecticides will not work. Montery has a special compound (spinosad) that controls rose slugs. No other spray I know of has spinosad. I suffered from rose slugs last year and as soon as I found out about this spray and starting using it, the rose slug problem got under control and disappeared completely.

Where can you buy the Monterey Spray? I've never heard of it...

I was wondering, too, so I found this site. Hope this helps us.

Here is a link that might be useful: Monterey Garden Products

I'll reiterate the response I put in one thread. Beneficial nematodes specific to sawfly larvae. My thrip and rose slug problem disappeared never to come back again when I used it 2 years in a row.