> the systemics are clear and compelling improvements over the pesticides
they replaced.

I am not convinced by this mantra.  It is not necessarily the pesticide that
matters, but often the way that it is used.  Pre-1985ish we saw lethal
pesticides being used and causing heavy losses of colonies; I am thinking in
particular of Hostathion being sprayed aerially on OSR (which wiped out
every insect) and the serious losses that we had with field beans (Vicia
faba) with farmers trying to control aphids (black fly).  Two things changed
- new pesticides came in (like Aphox) that could even be sprayed where bees
were foraging, but perhaps more importantly it became a criminal offence,
rather than just a civil claim, to kill colonies by the negligent use of
pesticides.  Local associations brought in Spray Liaison Officers to work
with farmers, who now were keen to avoid litigation; it only took a case or
two being brought to court to change attitudes completely.
In those days too, pest levels were checked regularly and only treated when
the economic damage threshold was approached: spraying costs big money.

Best wishes

Peter 
52°14'44.44"N, 1°50'35"W

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