Carol,

First of all, those 'exotic' aphids are not exotic at all. :P They are Oleander Aphids and are most fond of Asclepias. Check out my Monarch blog for more info (link below).

I prune my Milkweed all the time. No worries on the pruning, as long as you don't have any Monarchs ovipositing!

BTW: As far as the !@#$% aphids are concerned: I blast 'em off with water.

Here is a link that might be useful: tdogmom's Monarch blog

Poor ladybug! Predatory insects can't eat these aphids (and they know it, thus the bright yellow color); if they snack on a few, the beneficials will suffer consequences.

If the aphids are orange and black they are milk weed bugs and really only attack the seed pods and seeds. This can be good or bad thing depending on how many milkweeds you want. Mine usually disapear after a while.

As far as pruning, I'd wait anout 6 weeks, IMO.

Good luck, MP

That's a good point! It's very easy to confuse milkweed bug nymphs and oleander aphids. The aphids tend to be more yellow than orange.