Once upon a time on usenet Brooklyn1 wrote:
On Mon, 03 Aug 2015 11:13:58 -0500, zxcvbob
wrote:

We have a tropical milkweed that is frequently visited by Monarch
butterflies. Wife picks the eggs off and raises the caterpillars in
the house (safe from ants) and we feed them native milkweed
(Asclepias syriaca.) She has released at least 100 butterflies so
far this year. Anyway...

The aphids on the tropical have just exploded in the past week and
the plant is covered with them. What can I use to kill them without
harming the butterflies? Soap? Half-strength dormant oil spray?

Since the plant is in a pot, I suppose I /could/ hide it in into the
garage for a day or two if I need to use something stronger like
Sevin or Rotenone or pyrethrin. But I'd like to find a contact
poison that leaves *no* residue.

Thanks,
Bob

Aphids won't harm milkweed and they won't venture off the plant, I'd
leave well enough alone.

They do however stunt its growth considerably.
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)