Thanks for the pointer. It is indeed an exact match for Solanum americanum, a.k.a. American black nightshade, Small flowered Nightshade, common nightshade, white nightshade. And as Ken points out, CalFlora lists its toxicity as MAJOR. Cheers for the ID. Out it comes!

All different forms of helianthus are blooming now. Darned that we had such high winds today..I had a 12' tall one (jerusalem artichoke) fall down just as the first blooms were coming. In another location they were 8-10' tall and fell over then continued to grow to 6' above ground. Autumn has certainly arrived. Hope it's a long one.

Definitely a no-no, to collect plants, cuttings or seed from public lands, without a permit and I don't think that would be an easy thing to obtain from the FWS! The plant is an annual, so there are probably no commercial sources for plants. Best bet, is trying to locate a seed source. Maybe someone in the GNPS could help. It's possible that they might encounter some colonies of the plant during rescues, although I have been on dozens of rescues during many years and have never found one. Another source might be the Seed Exchange Forum here on GW. They produce a large number of small black seed that should be maturing now.

What you have might well be aphids. They prefer the nice tender, nitrogen rich new growth. Since aphids can, and do, start to produce live young even while they are still nymphs themselves you will have several generations on your plant before you notice a problem and as you eliminate one generation another moves in quickly to replace them, giving the appearance that those you though you eliminated have returned. Control is realy simple with just a sharp water srpay to knock those you can see off, repeated as necessary to keep knocking them off the plant. After a time you will see the numbers diminish, but keep on spraying them off untill they are no more.