Many, many thanks to Dwayne (dandjtaylor) in Salem, MA, for the advice of planting nasturtiums among the milkweed to control aphids. When my milkweed was about 2 feet tall, I had to squish aphids from a few of them. I planted the nasturtiums & once they took hold I haven't had one aphid!!! The milkweeds are now about 3 feet tall & so far so good.............keeping fingers crossed that this will continue over the next several months.
Dwayne, thanks again