Lately its leaves startit to go grey-ish dull color, curl up and die on entire branches, but they're not falling off. It seems like the branches are dying too, but only in a portion of a tree. The other half is still maintaining deep green leaves.
I've read that it could be a sign of verticillium wilt, but I'm not sure (I don't know if the photo is good enough to see it)

(It seems like my olive tree hates water, because every time I try to water it [the waterings, I learned, can't be less than 1,5 week away] it drops half its healthy-looking foliage, so that's why it looks so scarce)
Does anybody know what could be the problem? We survived a severe scale infestation and throught the summer it was growing nicely, I'm not giving up on it.