Reinfestation by aphids of a houseplant makes me wonder if the plant is occasionally put outdoors or if the insects are not aphids, but perhaps fungus gnats.

Plant never goes outdoors, and is surrounded by others which don't get the problem. Little dark spots appear on bottom of leaves that are too small to clearly identify even with small hand lens. All the sprays defeat them for a few days but by a week or so they return. fter a few days the leaf with the spots wilts and drops off. Plant is an ornamental sweet potato in very pale yellow green which I have grown inside for years, just revitalizing itfrom cuttings every time it gets too straggly. Several other varieties near it do not get the problem,

Are you sure it isn't scale? When was the systemic applied?

tj

My vote is spider mites. They are located under the leaves, are too small to be seen with the naked eye, and are very challenging to get rid of.

Any chance of pictures?

* Systemic is a granule turned into upper soil 15 days ago.

* Might be mites, but the systemic is supposed to get them also.

Could be it's still not up to the leaves. I'll keep doing the Sevin a few more cycles to hope it has a longer chance.

Do these dark spots move when disturbed?

At two weeks the systemic should at least start to work. To The Logician's point, are you sure the spots there now (if indeed insects) aren't already dead? What kind of damage to the plant do you see and could we at least see a pic of the damage?

tj