Someone used diatomaceous earth in the past for similar things. Not exactly sure if it was Hornworms though.

Bacillus thuringiensis is an organic biopesticide containing Bt, such as Monterey Bt Liquid. naturally occurring bacterium paralyzes the caterpillar’s digestive system without harming beneficial birds or bees. Or/and companion planting your crops with marigolds or basil. The strong aromas of these...

Go out at night with a headlamp, much easier to spot and remove. Also look into electroculture coils- I've trialed some in my various gardens around town and pest pressure in general goes way down