Bacillus thuringiensis (Bt) 
Not prohibited
Soil bacterium that produces protein crystals when it sporulates.
Characteristics
- Exists in several subspecies (kurstaki, aizawai, israelensis, tenebrionis).
- Some strains are approved as plant-protection active substances in the EU: they may only be used as authorised commercial products, never multiplied at home for that purpose.
Role in the preparation: Only as a commercial product authorised in the country; no homemade recipe on this site.
Caution: Buy an identified inoculant and store it as the label says; wear gloves and a mask when handling powders; check local regulations before any use.
Sources: Commission européenne – EU Pesticides Database (substances actives approuvées)
Documentary information: this is neither a recommendation for use nor a plant-protection or veterinary claim. Check your country's regulations before any use.