Since Bt is a microorganism, can it live in soil like other microorganisms?
Also, how can it be used on the grubs of the Japanese beetles that are right now buried about 2" down in the soil? Do you have to wait for them to emerge? Wait for the next crop of beetles to mature and breed, then hopefully treat the larvae before they burrow?
Quick answer top of my head because of personal business today---these Bt organisms are natural soil bacteria (somewhere not sure of the extent of range) But since leaf caterpillars and grubs aren't IN the soil eating they aren't affected.
Japanese beetle grubs are treated with Milky spore which is another organism--Bacillus popillae????I believe Milky spore causes an overall fungal infection, not a gut infection/ reaction like Bt. Beetle grub s won't emerge until they are adults and the Bts are said to only be lethal at the larval stage.
Got to go but will check later for followup if you like. Sally
I felt sure you were familiar with milky spore.
I guess the essence is that we currently don't know of a Bt organism that poisons grubs while they eat the grass roots, the way these Bts poison above ground larvae.
Here is the Bugfiles page for that guy http://davesgarden.com/guides/bf/go/234/
on which one commenter says it is.
"Leaf feeding caterpillars" is about as specific as I read about how many caterpillars are killed by Bt. I would have liked a more specific statement (all leaf feeding Lepidoptera larvae, or all Lepiodptera larvae) but haven't come across it.