So, is this plant in a container?

If so, I'd strongly suspect a cultural glitch, as in too much and/or too little water. Or an as yet inadequately developed root system (that is, short of water).

I would definitely inspect the root system (if possible) and try to eliminate that as a possibility. Is is root bound or are the roots rotting ?

To check for VW you could cut off a branch and look for brown discoloration in the vascular system (the "rings"). If you suspect VW, it's probably best to destroy the plant.

Thanks for your help jean001 and gingkonut. I don't really think it's a case of cultural mistakes, as I only water it when the soil is dry at a depth of 1 inch or so, but I guess anything is possible. I bought it last November in Tucson, so perhaps it's still adjusting to Albuquerque's higher elevation and cooler climate?? I'll check the vascular system and see what it shows.

Yes, it's in a container. It's starting to grow new leaves, and flower buds are forming, so hopefully it will be fine. Thanks again for your help.

cd

Well I cut off a branch and found no evidence of verticillium wilt, so that's a big relief. But I must be doing something wrong because it continues to lose leaves. Could it be a case of just needing to be fertilized?

cd

As it turns out, olives don't necessarily show the staining so often seen with verticillium wilt.

That said, VW is unlikely in a pot unless, of course, the pot is/was sitting on contaminated soil.

Further, to assure that the roots are okay, you can slip the rootball out of the pot to take a look. (Please tip the pot and slide the rootball out; don't pull on the stem/trunk.)

When it comes to roots and root tips, fresh and creamy color is good; dark and or black and/or dry is bad.