I have been growing calibrachoa hybrids (Million Bells) in flower pots for years with no problems whatsoever. I had twelve pots full of the most lush, beautiful blooms this year until budworms! I went to war on them but to no avail and am furious. I want to replant but first need to arm myself properly to fend off these pests. I assume it is necessary to replace all the potting soil but what is the most effective weapon as far as a pesticide, etc?
This article should help, though it's directed to roses it would still apply to your situation as well: https://www.gardeningknowhow.com/ornamental/flowers/roses/budworms-roses.htm
Yes replace the soil. You may even want to sterilize it. This article will help with that: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/sterilizing-soil.htm
Since they like to overwinter in pots, one of the best ways to prevent these little buggers is by replacing and repotting the soil BEFORE overwintering your plants. This way if there are any pupa in the soil, you will be getting rid of them and your plants will then be growing in good, clean pest-free soil.