bacillus thuringiensis shelf life

[Pat Kiewicz]

In article <3593AFA9.162B at umce.umext.maine.edu>, dbarry at umce.umext.maine.edu 
says...
>
>Dan Jones:
>> 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.
>
Speaking as a gardener, and squash grower, I can state without hesitation
that squash vine borer eggs are not laid *inside* the stem.  They are laid
*on* the stem at the base, occasionally on leaf petioles and tendrils, and,
when the vines begin to run, may be laid anywhere the vine touches the 
ground.  A quick brush with a finger is generally enough to remove an egg.
Late season (second generation?) moths prefer to lay their eggs on maturing
fruit, where they will tunnel in and make a putrid mess of a promising
pumpkin.

I have used MVP (a bio-engineered, Bt-toxin based product) injected
into vines to reach larvae after they had hatched, injecting small
amounts of concentrated MVP at intervals above the entry hole. In this
case, I can't say with certainty whether or not I'd manage to pin-hole
the larvae or feed them a toxic last meal, but the approach appeared to
work.  (Killing the adults and removing unhatched eggs is tedious but
reliable.)  

-- 
Pat in Plymouth MI
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