Quick B.t. overview

Chris Conlan conlan at adnc.com
Tue May 6 23:01:54 EDT 1997

There seems to be a fair amount of questions concerning B.t. (Bacillus
thuringiensis) bioinsecticides.  Here is a quick and dirty overview for
those concerned.  Basically, you can pretty much break down the B.t.
products into 4 major categories (spelling may not be perfect here as my
literature is at work!):

B.t. (kurstaki) - very commonly used and in many products like Dipel or
MVP.  One of the most common targets of this strain is the Budworm/Bollworm
complex of Noctuid moths.  It is broadly Lepidopteran active.  It is not
known just how many species this strain will kill (or any other strain for
that matter) but it is not active against all Lepidoptera.  There are many
species unaffected by it.

B.t. (aizawi) - probably the second most common B.t. strain on the market.
This strain is also broadly Lepidopteran active.  It is most commonly used
to combat such pests as Armyworm which the kurstaki strain does little to
stop.  Some products contain combinations of this strain and the previous
(as well as some others).

B.t. (israelensis) - This is the Dipteran active strain most commonly used
against mosquito larvae.  It is active on several species of Diptera.  It
has not been found to be active (at least at commercially acceptable
levels) on Leps.  (if it is, I have not heard of any yet)

B.t. (tenebrionis/san diego) - this strain is coleopteran active.  Its most
common target is Colorado Potato Beetle.  It does get some other species as
well, but does not seem to have as broad a spectrum of activity as the Lep

There are many other strains out there and several of these are currently
found in existing products.  There are also many being developed for future
products or as part of resistance management programs.  B.t.'s also don't
tend to be very persistent (at least on the target species).  Most of them
degrade within just a few days after application (especially under sunny
conditons).  Also, the formulations on the market don't transfer well from
bug to bug.  It's not like a bug can fly to a B.t. sprayed field and then
fly to a clean field and cause an epidemic in the untreated field.
These products really are extremely safe for mammals, fish and birds (bees
too!).  We just don't know how far reaching the effects are on some of the
related non-target species that may get sprayed along with the target bugs.
Get used to them though.  As the public outcry for safer food continues
B.t. use will only increase.

conlan at adnc.com

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