bacillus thuringiensis shelf life

[Anne Kilmer]

Chris Conlan wrote:

> >The stuff is a spore forming organism, very stable when in that form and when
> >introduced into the soil.
>
> While it is true that B.t. is a spore forming organism it is not the spores
> that are responsible for most of the mortality.  (Forgive me if I'm stating
> information you already know, but others reading may not).  The vast
> majority of death is caused by the protein toxin (crystal in form) found
> within the bacteria.  Commercial formulations are grown to maximize the
> amount of this protein so you get a nice bang on the bugs for the first day
> or two it's in the field and then those proteins break down in the
> sunlight.  Any mortality caused by remaining spores is virtually
> negligible.  This stuff does not go hog-wild after being sprayed and
> proliferate like crazy in the soil.  Rather, it quickly fades to background
> levels and is of little further concern.  Also, if still worried, you can
> buy formulations of B.t. that do not contain spores and therefore cannot
> proliferate.  Examples of this are products sold under the trade names MVP,
> Mattch, M-Trak and a few others.  I hope this helps and I get the feeling
> it won't be my last post on this (I had to go and open my mouth!).
>
> Chris
> conlan at adnc.com


See, Chris, you're why I feel relatively confident that we're not all idiots
carelessly poisoning the environment. Your helpful, thoughtful posts reassure me.
(Not that the rest of you guys aren't wonderful too, but this is Chris' field.)
What scares me is not so much the Bt used for caterpillars, but the variants aimed
at mosquitoes, which otherwise-intelligent friends of mine think we should
broadcast over lakes and canals in South Florida to remove the mosquito problem. I
don't know how many othe aquatic insects this would take out, and our ecology is
fueled by mosquitoes as well as caterpillars.
    Then there's the ones used on beetles, which I fear are not species specific.
I'm fond of beetles.
    My concern is that the people applying these nostrums are not as smart and as
careful as the people creating and testing them. And sure, it was worse when
everybody and his little sister could dust their lettuces with Paris Green.
Cheers
Anne Kilmer
South Florida