My gaura have been doing well here in Southern California. However they have been infested with ants and small oval brown things attached to the stems. The parts of the pant that has these turns a black/brown and looks greasy as if I had sprayed them with oil then tossed dirt on them.

They continue to bloom but not as well. I did spray with the hose, didn't seem to bother them. Tried Neem oil to no avail, then finally bug spray...nothing.

Ants are working furiously to "tend" the brown things. And the plants are beginning to look creepy and greasy.

What is this?

The guara are in a succulent/cactus part of my garden and do not get heavily watered.