I'm thinking about growing borage for the first time as well. The suggestions I've read says to eat the smaller new growth.
Last year, I had a huge success with deterring hornworm, but I'm not sure what did it. Here's the situation. I took over my brother and sister-in-law's garden, where they'd planted some tomatoes but not much else. Of course, I want to grow everything, so I planted something like 15 different herbs, several different vegetables, and a few different flowers. My sister-in-law kept saying, "Watch out for the nasty worms. I don't see them yet, but we always get them on the tomatoes." And when she described them to me, I knew that she was talking about hornworms.
The thing is - they never showed up! No hornworms!
I planted basil with the tomatoes, and onions nearby, and some other herbs not too far from that, and flowers and cucumbers and pumpkin . . . lots of stuff packed into less than 300 square feet. I saw lots of different kinds of wasps, so I'm thinking that maybe some of them carried off the hornworms while they were still small, before I ever even noticed them.
Or - and this is my primary theory - I suspect that birds perching on the playhouse/teepee I made from scrub trees cut out of the fenceline swooped down and ate them. You can see in the picture that my tomatoes are supported with bamboo, but I didn't often see birds perching on them. More often, they were on the taller structure with cucumbers and other stuff growing on it.
I think I'll do a similar structure this year to make sure that the birds have a place to perch so that they can eat all the bugs they want.
