Biological Warfare: Destroy All Caterpillars!

July 26, 2006 11:52 PM

Any recommendations about the use of Bacillus thuringiensis? I've got some nasturtiums that are being devoured by caterpillars, and I'd like an option that's a little simpler than "pick them off by hand".
posted by Guy Smiley to home & garden (6 comments total)

I've been off the organic orchard for 5 years now so I am a little rusty. Here is what i remember. I was spraying apples against the codling moth. (What's worse than finding a worm in your apple? Finding half a worm.)
BT degrades in sunlight so you want to spray it early in the day. It gives the bugs a terminal stomache ache so the effect is not instantanious. They have to eat the BT before it can kill them. I used a powder that I mixed with water but I don't remember any additions to improve stickage. It was all pretty straight forward on this end. For me, the critical part was timing the spray for just before the major hatch. It doesn't sound like you have that problem.
posted by pointilist at 7:11 AM on July 27, 2006

I used it, and from what I saw the liquid form you attach to your hose works great. The powder form seemed less effective.
posted by atchafalaya at 7:53 AM on July 27, 2006

I doubt BT will control codling moth, since the larvae eat the inside of the apple, which you can't treat. More here.
posted by weapons-grade pandemonium at 9:15 AM on July 27, 2006

BT should work for the nasturtiums. Use the hose sprayer, as atchafalaya says.
posted by weapons-grade pandemonium at 9:18 AM on July 27, 2006

I would identify the caterpillars first--take one to the nursery, and they'll know what it is and how to treat it organically.
posted by weapons-grade pandemonium at 9:21 AM on July 27, 2006

w-g p- It will. they have to eat their way into the apple. You still get a mark. Using phermones to disrupt their mating cycle is a better solution if your orchard is big enough for it to be effective.
posted by pointilist at 9:09 PM on July 27, 2006