It’s delightful when caterpillars eat the plants enthusiasts grow for them. We watch them grow, pupate, and emerge as beautiful adults. We release them into our yards and other areas. BUT …
… before long, while using the same plants once they grow new leaves, there are caterpillar disease issues. We didn’t treat the plant with insecticides. We can’t figure out why they are dying.

If we have used living plants and reuse the same plants, what about the disease pathogens they may leave on the plant, pot, and soil? Some butterfly diseases are so slight that they aren’t noticed at first. After a while, the pathogens build up and young caterpillars, the next generation or two, eat the pathogens after the plant has grown new leaves.
If only there was a way to protect the pot and soil! Oh, wait … there IS!
Simply take a plastic bag and cover the pot. This is a great use for plastic grocery bags. Tie it tight around the stem.

Once caterpillars have eaten the leaves, cut off the bag and dispose of it. Cut the plant back to only a few inches tall. In a few weeks, it will bush out and be ready for more caterpillars.

If you water the plant well before tying the bag shut, you won’t need to water it again until you take it out of the popup habitat. The plastic bag usually keeps the soil moist for a week or more.