This year I am planting into "grow boxes" and upon mixing the soil, found cut worms. They are small yet and there are a lot of eggs. I want to treat this problem before I transplant my starters into the boxes. I can go buy a mix at the store but that can only be a temporary fix, which leaves me with the problem that I will have not curbed the life cycle and, therefore, am exposed to future infestations. Is there a safe way to eliminate these pests from my mix permanently, as I have a large volume and want to save it, if at all possible?