bacillus thuringiensis shelf life
semjase at aol.com
Fri Jun 26 20:39:07 EDT 1998
><HTML><PRE>Subject: Re: bacillus thuringiensis shelf life
>From: dbarry at umce.umext.maine.edu (Don Barry)
>Date: Fri, Jun 26, 1998 11:24 EDT
>Message-id: <3593AFA9.162B at umce.umext.maine.edu>
>> We've been plagued with squash vine borers
>> both this year and last, and I've been trying
>> to exterminate them using "Safer Caterpillar
>> Killer", a product containing bacillus
>> thuringiensis (B.t.) var. kurstaki.
>I'm embarassed that I didn't see this before but I was caught up in the
>shelf life/proper application issue: Bt will not control squash vine
>borer. The eggs are laid inside the stem and the caterpillar develops
>within, isolated from any topical sprays. I doubt injection will work
>because Bt is a stomach poison and an injection would deter feeding.
>Control efforts are usually aimed at managing the adult by a series of
>weekly residual treatments right on the base of the vines.
>> it is unfortunate however that the material
>> is living and can become established in the
>> soil much to easily. Ever think of Anthrax?
>It's true that there are pathogenic species of Bacillus but Bt is not
>one of them. It does not infect man and it doesn't really infect
>insects. The chemicals involved in producing the spore just happen to be
>active against certain insects when ingested. These chemicals are not,
>in themselves, toxic and only become active when thay are cleaved by gut
>enzymes. The spore forming chemicals of Bt kurstaki are cleaved to toxic
>fragments in lepidopterous guts. If another type insect ingests Btk, it
>is cleaved to different, non-toxic fragments. In the same way, Bt San
>Diego is toxic to beetles but no other groups. Actually most of the
>bacteria in Bt formulations are dead or absent. It doesn't matter if
>they are there or not because it's the spore forming chemicals (which
>crystalize and can be isolated) which are insecticidal. In fact many of
>the newer Bt products are isolations of specific chemicals derived from
>the spore forming crystals and entirely devoid of any bacteria.
>Univ. of Maine Cooperative Extension
>Pest Management Office
>491 College Ave.
>Orono, ME 04473-1295
>Toll free (within Maine) 1-800-287-0279
>Email dbarry at umce.umext.maine.edu
This is somewhat correct but the things I am trying to point out is that the
bacteria are not normally found in nature in the concentration agricultural
uses cause. The use of a biological agent is risky business and should not be
Anthrax kills humans and other animals, it lives in the soil. B. thuriengensis
also lives in the soil and kills lepidopters and others insects. Once the soils
are contaminated elimination is difficult.
Case in point:
We used to have many Mourning Cloak butterflies here. Some individuals decided
to spray the elms with Bt. I was vehemently against this but of course the all
knowing did it anyway. The result is a devastation of the population to the
extent that it is non existent for all practical considerations. It has been
10 year since that debacle and almost all leps are gone. Yeah real great
Who speaks for the butterfly?
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