I understand that Bacillus thuringiensis (Bt) breaks down naturally,
but I'd like to know how. I'm going to be applying Bt powder, and the
instructions say to do it roughly weekly, and especially after it
Now, does this mean that Bt powder loses potency when wet, or just
that it gets washed off the plant? Hard to imagine the former since
you can keep a spray bottle of the stuff dissolved in water. I know
that sunlight breaks it down, but does that mean that if cultivated
into the soil it stays there for longer, such that it kills grubs that
are just hatching there? I've also read that dry spores have a shelf
life of several years (implying that wet spores do not).
Yes, I know you want it on the plant, so I know that you want to
reapply if it gets washed off. But what if it just drizzles?
First off, I never said it was a chemical. That actually doesn't have
anything to do with my questions.
Perhaps I should have phrased it differently. What makes the stuff
die? Something must make it die, or else it would be hanging around
buried in the soil forever.
And the answer to my question doesn't appear to be there, nor in the
half-dozen other websites I looked at.
First off, living things die, diminish, bring down the final curtain, or
join the choir invisible, they don't break down.
Bacillus thuringiensis disappears from plant surfaces rather quickly
however they are moderately persistent (whatever that means) in soil
(their natural habitat). They are fried by ultraviolet light.
There are no lobbyists for cover crops and crop rotation. Why?
The problem is it washes off fairly easily and as it is not absorbed by the
plant this means it is not available for the grubs to ingest. This is
inconvenient but also one of the reasons why it is so safe, it works by the
bacteria attacking the gut lining of grubs and they must eat it it for this
to happen. But this means it doesn't effect anything else. So no it
doesn't effect anything in the soil.
The instructions to apply it regularly are intended to give full coverage
and of course to sell more BT. If you can deal with the odd hole in your
cabbage it is fine to just apply it when grubs or caterpillars are evident.
You don't need it at all when the season is too cold for the insects to be
actively breeding and laying eggs on your leafy veges.
OK, but I'm told that borers can live in the soil, and emerge the
following season. That's why floating row covers are not necessarily a
good idea for borer control. But following the logic here, if Bt
washes off the plant and gets into the soil, wherein it is tilled in
to make sure sunlight doesn't hit it, why doesn't it just kill those
emerging borers? I can only imagine that it's because it doesn't last
a long time in the soil. Why? It lasts a long time dry, and it lasts a
long time dissolved in water. So why won't it last a long time in
dirt? Eventually, I should just be able to take dirt shaded by a plant
I've been dusting, and just throw that back on the plants to keep them
This is really a very basic question. What causes Bt to break down
(die, diminish, pass away, expire, croak), other than sunlight?
Because it isn't a poison as such, it is a microorganism. Grubs and
caterpillars need to get it into their gut by eating it for it to be
effective, which is why you put it on to leaves and other parts of the plant
that makes up their diet, they don't eat dirt.
That makes some sense.
But again, if my soil gets "infected" by Bt with repeated
applications, I can stop buying the stuff and just
dust the leaves with the infected soil year after year, right?
That is, dryness doesn't kill it. Wetness doesn't kill it. So where
does it go, once it's in soil? I guess
something else in the soil must kill it. Nothing to live on there?
Well, I'd say the same thing when it's
dissolved in water, but it seems to do just fine that way. Powder and
liquid forms of Bt are active, I am told,
Goggle is wonderful..full of wonder but we must know in advance what
we are seeking. Good thing or this computer stuff would scare the
........ out of me more so.
Key word is half life.
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