Copper doesn't really hurt anything; so a copper oil spray... as long as the air temp is below 80F is a simple and innocuous treatment.

Hard to tell from the photo if it is greasy spot; but that anomaly on Meyers usually affects the oldest/lowest leaves; and is usually the result of unclean orchard floor.

I think not.

Citrus is an important crop in CA and is well researched. Considerable info is online from the Univ of CA for both home gardener and commercial growers. No mention of greasy spot for either grower.

Now if you lived in FL, that would be a different story.

Here's the Univ of CA page for citrus
http://www.ipm.ucdavis.edu/PMG/GARDEN/FRUIT/citrus.html

It's difficult to make a diagnosis when the image is of such a small portion of the tree. I suggest something is awry culturally. Review the info at the link for insights.

Here is a link that might be useful: citrus in CA

Thanks for the link - it's not obvious to me what the problem might be after checking out the site. I'll look around some more. Thanks for getting me to focus on California problems - makes the job easier.

Looks to be a nutritional issue.
- Is it in a pot or the ground?
- What sort of fertilizer program do you use?

Hi Jean:

This tree has been in the ground for almost a year. It got a full dose of the following fertilizer in May:

***
GRO-POWER Premium Citrus & Avocado Food 8-6-8
Ideal for all citrus, avocado, fruit and nut trees, as well as grape and berry vines.

40% Humus, 8% Humic Acids, Controlled Release Nitrogen, 4% Magnesium, 4% Sulfur, 2% Iron, micronutrients and soil penetrant.
***

I am not sure what my next step is...

Okay some final thoughts... what you are seeing is history; it happened; you can't fix it; you can only move forward.

When I see round spots, I always think fungus; but when I hear hoofbeats, I think horses; but it could as well be zebras.

Despite what the gurus of UCD (my alma mater) and UCR (the ivory tower gurus) think; I am NOT convinced there is no greasy spot in Southern California; all the conditions are there for it.

Sometimes spider mites will leave a legacy that looks something like that. The important thing is to continue to treat the plant well and see that the new growth Is healthy and happy.

Finally, the "ideal" fertilizer for all citrus of 8-6-8 is a good product; but is not ideal for Meyers. Meyers need a ratio of 3-1-2, and a lot of it.