Have no idea but you can try spraying with pyrethrum - I use that to rid all nasty critters. I do check for benefial insects first, though; no need to knock them out, too.
Cait

I get moth caterpillars on several of my salvias this time of year, mainly on the S. greggii/S. microphylla cultivars and S. puberala, although I noticed a few on S. melissodora last week. Bt (Bacillus thuringiensis) works well. If I spray once when I notice the first damage I find that I don't have any more trouble the rest of the season.

I had huge Noctuid caterpillars snarfing my prized Salvia praeclara I had nurtured from a seed, I picked them off and gave them the old Virginia Tech bug stompers treatment. Grrr.

Joseph