I live In san Diego and have been growing medicinally outdoors for the past 5 season and only these last 2 season did I use BT to prevent and deter caterpillar infestations. I've always tried to avoid any pesticides or anything that's not organic on my fruits as I am a strong believer in natural methods being the key to healthy medicine. Caterpillars can be the equivalent to a plague of locusts depending on how you deal with them. Even in a green house with a UV-C / HEPA Air Purifier unit installed those little bastards some how manage to finagle there way in in the mid weeks of flowering and all it takes one or 2 of those white moths, yellow moths, to lay hundred's of hair like egg's just waiting to burrow into the leaves and later erupt havoc unto your precious fruits of labor. With the eggs in place the parasitic larvae becomes dependent on your plant and literally grows into full adult stage in less than 3 weeks, by that time the little fuckers have vapiristicly sucked the vital essence that was needed develop the oil oozing thrichomes that you diligently worked for and sought after, yet is destroyed if one is not prepared. Anticipating an attack on a species that matures from larva to mature breeding pupa in such a short time can be hard to foresee. The life line and nature of these monstrosities that eat constantly, leaving trails of little black crap balls inside of your once gorgeous kola's that seemingly spontaneously combust, not on fire but into black mold, as there shit contains the foundation for even more problems.... Literally shitting all over your hard work, and these endomorph's life cycles from egg to cocoon to breeding adult only takes less than a month. So If your In Southern California, and you plan on going outdoor with your fruits, I would totally recommend BT as a preventative and a counter measure, as it is a safe and bio-degradable/ biological warfare against these pesky little guys. Use Caution though, I've noticed that when spraying with bt that it will increase your chances of developing PM: powder Mildew if you spray at night, so you have to be careful what time of day your spraying as to prevent stagnant water deposits that can develop unwanted fungal culture and spread nasty spores throughout your garden. I tend to spray early as possible, 1-3 times a week so that the moisture will evaporate, as to prevent pm. Hope this was helpful, #dabLyfe. #FuckCattipilars