I agree. Hosing them off works really well. I have a rose that attracts THOUSANDS of them when it leafs out in spring. I use a sharp spray of water - it's really satisfying to knock them off. It's my first step, and in most cases it is enough if done a few days in a row. I would really encourage this approach - completely organic, effective, and cheap.
I also agree that insecticidal soap works well. You do need to hit them directly.
On the non-organic level, which is hopefully the last resort, acephate works well (Ortho Systemic Insect Killer). I have lots of japanese anemones, with thousands of leaves, and they would come back repeatedly after spraying and insecticidal soap and I would get a tremendous amount of sooty mold on the leaves. One application of this took care of it.
Ecrane is on the money on the population. Female aphids can reproduce in the absence of males - they simply reproduce themselves. In addition, here's a clip from an article about the rate:
"Each of the many aphid species has its own life cycle, but there are some features uniting nearly all of them. One feature most species share is that they are incredibly prolific. Wingless adult female aphids can produce 50 to 100 offspring. A newly born aphid becomes a reproducing adult within about a week and then can produce up to 5 offspring per day for up to 30 days! The French naturalist Reaumur during the late eighteenth century calculated that if all the descendants of a single aphid survived during the summer and were arranged into a French military formation, four abreast, their line would extend for 27,950 miles, which exceeds the circumference of the earth at the equator! "
So you see what your 2 can do!
Donna
Donna
