bacillus thuringiensis shelf life

[Semjase]

>>The toxin is produced by the living bacteria.  The spores germinate in the
>gut,
>>produce the toxin (thurien I believe) which causes paralysis of the gut,
>then
>>the bacteria proliferate in the gut destroying the larvae.
>
>Close, but not quite.  The insect ingests the bacteria with the protein
>toxin crystal.  The crystal is then broken down in the alkaline environment
>of the insect gut and activated.  There it binds to the gut wall causing it
>to basically ulcerate.  The gut contents then leak into the main body
>cavity and raise the pH to lethal levels.  This process can take days.

Ummmm, The bacteria then grow in this nutrient soup.  Besides the gut is
paralysed in this process also. Yes there is also ulceration. 
>
>>
>>A pure toxin prep would be limited much more in its effect and by
>deteriorate
>>quickly.  I do not at the moment have the information on how long it will
>last.
>
>Some formulations contain a mix of spores and toxin crystals while others
>contain only toxin crystals and there is little difference in efficacy
>between them.  The spores can enhance and speed up the rate of kill
>somewhat but it's not all that dramatic.  It's the toxin already in the
>formulation that is responsible for most of the mortality.  I have been
>involved in the testing of numerous formulations and strains of B.t. and
>witnessed this first hand.  Feeding the insects pure spores does not cause
>anywhere near the mortality that the pure toxin prep does.  While it is
>true that the spores may persist in the soil for a long time, they just

They do not persist but germinate and establish the bacteria in the soil.  The
contamination vectors are obvious.

>don't cause the kind of widescale mortality you are describing.  If B.t.
>was the persistant killer you seem to think then why do farmers and
>gardeners constantly need to re-apply it to maintain control of their
>caterpillar problems (even in areas with no resistance problems)?  Heck,
>the agricultural community would be dancing in the isles if you only had to
>spray something once in a lifetime to control your Lep pest problems

If such an item was discovered it would end up being a secret.  What pesticide
company is going to put out a product with that kind of performance.  They be
out of the business along with everyone else in that industry. 
>(something legal anyway!).
>
If a gardener uses this stuff he is making a grave error.

Farmers grow monoculture and spray yearly because they do not want to chance a
recurrence.  If confined to the farm the damage to outlying areas is mitigated.
>I'd like to point out that I'm not advocating everybody go out and spray
>B.t. all over the place.  It's just another tool for insect control that,
>when used properly, is much less harmful to the environment than many of
>the other options that exist.

Sorry but I cannot recognize that as true.
>
>Sorry for the lengthy posting.  I'm outta here.
>
>Chris
>conlan at adnc.com
>
>
></PRE></HTML>
Nothing to be sorry about Chris!

S.