Here is a homemade recipe for hornworm food I found in a pdf document:
1 cup (100 g) of non-toasted wheat germ
1/3 cup (25 g) of non-fat dry milk
4 tablespoons of agar
1 teaspoon pure raw linseed oil (non-boiled)
1/2 tablespoon nutritional flake yeast
1 vitamin C tablet (1000 mg)
2 vitamin B tablets
2 multivitamin tablets
1 tablespoon of table sugar
2 1/2 cups water
1. Place vitamin tablets in blender and reduce to a powder. To this powder, add the wheat germ,
powdered milk, and sugar and blend until the dry components are well-mixed.
2. Remove the dry mix from the blender and add 2.5 cups of boiling water. While mixing at low
speed, add the agar. Be careful to replace the lid on the blender before turning it on. Blend for
one minute and then add the dry mix and continue to mix.
3. Add the linseed oil and increase blender speed. You may need to manually blend the diet
while the blender is running. The diet gets rather viscous at this point.
4. After blending for about 5 minutes, add the nutritional yeast flakes and continue blending for
another minute. Components in the yeast are heat labile, thus, yeast is added as late as possible.
5. Once the diet is thoroughly mixed, pour it into a plastic tray that has an airtight lid. The
diet will solidify and remain usable for about 7 to 10 days if kept refrigerated.
The hornworms will ultimately die on anything you feed them unless it is their chow or of their prey plants (pepper, tomato, or tobacco). Unfortunately, all of the plants that they consume in nature are toxic for herps.
Hornworms will eat mulberry chow that is meant for silkworms, but they won'y be able to pupate properly on it. You can try feeding oak leaves or mulberry leaves if you can find some that you are certain have no been sprayed and they will likely eat them to survive. You can also try certain leafy greens, and I've have flaky success with butternut squash and other harder veggies like grated carrots... these foods will keep the worms alive with something in their gut but they will not "thrive" on it very well so try to feed them off as quickly as possible on this diet.
Once they are big and run out of food you can refrigerate them, not many suppliers will tell you this because they want you to re-buy more but I'd rather give out all the info that i can to people then a sale. This is what you do for next time..HOW TO TAKE CARE ON THEM
Once they grow to adult size you can put them in the refrigerator(take them out of the cup place in a brown paper bag with some newspaper in it to double insulate) they will go dormant for up to 2 weeks. When your ready to feed them bring them to room temp.