So first of is Bt. There are several strains of this bacteria and they kick a moth's butt and are not toxic to humans. Once I had this tomato horn worm that I was growing fat because I was going to try to eat it. Bear and some of his friends put it in a cage and I was feeding it non Bt tomatoes. Well Gretchen decided that a partially sprayed couple leafs wouldn't hurt, but the next day that dude was dead. I had one of those kids back over last week and he was like where's that horn worm in the cage?
Here's a moth larva on my asparagus!
Here's the solution.
So you just mix a Bt powder in water and spray it on. Once the larva ingest some of the bacteria their jaws lock up and they die the next day. There are several strains of Bt. I have had this Bt aizwazi for 3-4 years in dry granules and it is still kicken. It's also good for wax worms in your honey comb which is what I originally bought it for. It's worked well on my tomatoes, tobacco, and now my asparagus.
Here's a link explaining the various pro's and cons http://www.ca.uky.edu/agc/pubs/id/id156/id156.pdf
Here's the tomato that was being eaten before I sprayed. Next to it is a Bt that kills gnats.
That tomato looked like someone took a bite out of it the day I sprayed it, but the next morning a callus had formed. The gnat Bt is called knock out gnats. It works pretty good in the house. I recommend putting it in your potted plants as some of those are the gnat homes.
Pyola is the next one
Pyrethren is a extract of the chrysanthemum flower. My neighbor who is an avid anti-chemical gardener who grows a ton of food and is a vegetarian loaned me some for my squash. I've had to apply it a couple of times but it does kill the squash bugs. It is an approved organic pesticide and is applicable up to the day of harvest. Unfortunately I should have Bt'd the squash because it has stalk borer larva and now they're in the stalks. Some squash varieties are more resistant to those stem borers. I did Bt those sunflowers behind there so I can get more seed though. The Pyrethrins are in an oil and you just mix water with and spray. It's a contact killer.