I am ruining a small family business for herbal tea in Armenia. We especially focus on production of mint. We used to keep dried mint in cupboard boxes for a few months before it gets to the clients. It is a business-to-business type sales, so we cannot pack it in sealed packs. We sell in paper packs to the clients.
Recently I have notices some small, 2-3 millimeter long worms in the boxes eating out the mint, which later on evolve into little butterflies. Is there any food-safe chemical that I can apply to get rid of these worms?
The safest "chemical" is probably Dipel (Bt, or Bacillus thuringensis v kurstaki). If what you have a Indian meal moths, the pheromone traps work quite well at removing the adults who are laying the eggs but take time.
You can probably kill the existing larvae by freezing the dried mint, though. Freezing may or may not kill the eggs depending on what you have.