serge, can you post a photo of the entire tree, and then some closeups of the affected leaves? This looks to me either like a virus or possibly something physical, like damage from a spraying of something. You can always send this to your local Master Gardener or Extension office for ID as well, and include all the photos mentioned. Where are you located, you don't indicate in your Zone field. That makes a big difference.

Patty S.

I was going to guess some sort of chemical application when the ambient temperature was too high; but without the benefit of more information, it is just a guess.

WHOOPS this was a Golden Nugget mandarin - sorry it can get confusing back there.

I am in zone 10a, in alameda, ca. It's been hot of late (80) but nothing out of the ordinary. I fertilize with an 8-6-8 with micronutrients. I don't spray on or around with anything.

Thanks!!