Subject: Re: P. Brassicae

From: "A.P.K.Torry" <[email-masked]>
Date: Thu, 27 Jun 1996 09:23:31 GMT

What has dessimated the Brassicae population ?

1) Is it insecticides?

2) Is it Apanteles glomeratus ?

3) Is it global warming ?

4) Is it Granulosis virus?

5) The European common agricultural policy?

Comments additions and discussions please

I think it is item 5

Andrew Torry

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From: [email-masked] (Chris Raper)
Date: Mon, 01 Jul 1996 21:54:40 GMT

>Comments additions and discussions please

I don't know why the brassicae (and to a lesser extent rapae) are
declining but not napi. But a clue might be their foodplant
requirements. As far as I understand (and I am no expert) brassicae &
rapae both like to eat garden/crop brassicas (cabbages etc) while napi
eats wild crucifers.

Another point to note is that, if the decline is due to pesticides and
pest resistant cabbage crops, the old (high) populations may have been
artificial and what we are seeing now is more like the correct level.
The high population over the last 100 years may just have been a side
effect of Man's agriculture.

I don't know for sure if any of this is correct but it is worth a
thought.

Chris R.

--
All views are my own and are not necessarily those of my employer.

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From: Andrew Syred <[email-masked]>
Date: Mon, 1 Jul 1996 08:42:40 +0100

In article <[email-masked]>, "A.P.K.Torry"
<[email-masked]> writes
>What has dessimated the Brassicae population ?

Didn't realise it had been, millions of the things around here muching
me cabbages.

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