On 4 Jun, 19:20, "Robert \(Plymouth\)" beachcom...@ultimate-
anonymity.com wrote:
wrote:

: I'm sure this is a pretty common topic for discussion and I've checked
: the archives for the answer I'm looking for without success.
:
: I used up the last of my stock of granules last year (Bromothos wasn't
: it?) and as I gather there isn't a chemical replacement, decided to
: got the mechanical root and make collars from 4" squares of roofing
: felt.
:
: Can someone tell me at what point of the season I can retrieve these
: bits of felt off the plants for re-use next year. ie when does the
: risk from the flies cease?
:
: Thanks
:
: Rob

Several generations over the summer it says herehttp://www.abdn.ac.uk/web/test/organic/research/cabbage_fly.php

Yes that's what I found but as only one dose of the original Bromothos
was effective at planting I'm surprised that I need to keep the
collars on for the whole life. I was hoping that someone would reply
from trial and error experience. Having planted something approaching
200 sprouts, broccoli, cauliflower, etc. and made the corresponding
number of collars I was hoping that I would be able to retrieve them
after a month or so otherwise the expense and effort is even worse
than buying a tub of powder.

Rob