Uhoh. Root mealybugs.

Thanks for the id rhizo_1, i had not heard of them before.

I'd much rather incinerate the affected area than drench my herb garden with pesticides. Are there any less drastic measures to get rid of them?

These insects are very difficult to get rid of, more so than most. I am with you on the course of action, no question about that. I might consider applying a layer of horticultural grade diatomaceous earth before planting other plants anytime soon.

You know what might be cool to try? Soil solarization. Pull out the plants and cover the ground with sheets of black plastic for a couple of the hottest months of the year. It just might get hot enough to finish them off. (From what I understand, they don't go more than a couple cm below the soil surface.)

Solarization can only be accomplished with clear plastic. But you are right....this might be an instance where proper solarization would solve the problem!

If you think you might be interested, let me know and I'll lead you to some appropriate informational sites. What is the climate like in your part of the world right now, by the way?