Fw: Re: Painted Lady Migration

[mbpi at juno.com]

Hi all,

Thought I'd share this interesting adjunct I received from Ernest
Mengersen. (Hope you don't mind Ernest!)

No wonder corn popped in Canola oil tastes so yummy!!

Mary Beth Prondzinski

--------- Forwarded message ----------
From: "Ernest Mengersen" <emengersen at admin.oldscollege.ab.ca>
To: <mbpi at juno.com>
Date: Mon, 30 Apr 2001 20:32:44 -0600
Subject: Re: Painted Lady Migration
Message-ID: <saedcc28.078 at gwmail>

Thanks Mary Beth:

It is interesting that someone on another list-server has also followed
them north and they were observed today in southeastern Washington.  It
is important and interesting to us because the painted lady larvae feed
on Canada thistle, a serious weed in both Canola and alfalfa crops. 
Since all three plants are broad-leaved, there are no herbicides that are
really effective.  The painted lady larvae tend to clean out the Canada
thistle and leave the crops alone (Canola in the Brassicaceae and alfalfa
in the Fabaceae).  As one rancher told me - the best biocontrol we have
for Canada thistle.  But they do not arrive every year and do not arrive
early enough to put good pressure on the thistle.  (some common name
problems here as many call it the thistle butterfly or thistle
caterpillar).  

It can occasionally become a pest itself in sunflower crops.  It is
interesting that it is considered a pest in Canola because its fecal
material is a similar size to the Canola seed and thus the frass becomes
a contaminant in the harvested seed.  It is a problem only in years when
V. cardui is abundant and when the larvae have not matured well in
advance of the harvest.  It is an infrequent problem.  I teach it as
such.   The difference in price to the farmer can be as much as $4 per
bushel (with an average crop of 30 bushels per acre) you can see the
effect of  its presence in a crop can be costly to the farmer.  Does not
reduce yield - possibly helps it - but a contaminant.  

Yes, I look for it every year but it is only common about once in five
years.  I am sure its status and contamination problem will change as
most farmers are now planting the Roundup-tolerant Canola varieties and
so Canada thistle isn't the problem it used to be.  The use of
Roundup-tolerant Canola varieties opens up a whole other new ball of wax
as the Europeans don't seem to want our GMO Canola.  We sometimes have no
idea what we do to ourselves and the problems we create.  

I still have not seen my first butterfly of the year but have had a fair
moth catch.  Take care and thought I would share this tidbit with you.

Ernest


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