Hi Reid: I had similar brown spots on older leaves on my navel orange. Most of the old leaves have fallen but some greener leaves continue to have the brown spots. I just got the house this year and attributed my issues with the brown spots and citrus leaf miner to the underwatering and bugs. (Short sale and previous owner we think gave up) I don't know though as I am pretty new to citrus as this is my first year with a a tree. I hope someone with a bit more knowledge pipes in on the issue. Good to see some other people in SoCal growing citrus.

Also one other thing I forgot to mention is my tree is doing a lot better with proper care and watering. It's not nearly perfect but seems to be producing a decent amount.

I have those spots as well on a thornless key lime. It had them when I got it on the older leaves. None of the new leaves have them and the tree appears fine. I have no idea what they are though.

Difficult to say without seeing the underside of the leaf; but it could be greasy spot fungus. Could also be something like spider mites. At any rate, the damage was done in the past; and if your new growth looks healthy you are okay. You should treat your tree once or twice a year with fungicide, topical or systemic; or maybe copper oil. Important thing for fungus is to keep the floor under the tree clean.

Same pictures, same text, additional responses, on different thread - see

http://forums.gardenweb.com/discussions/4311792/need-help-identifying-disease-or-pest?n=2

Hmm...that looks like what I thought was black citrus aphids on my Ponkan which I wrote about in another post. It is strange how it keeps going after that one tree. I keep spraying and cleaning it off with oil spray or soapy spray but it keeps reappearing. I hope it does not spread to my other trees. The new leaves are beginning to harden up on the tree now so I hope the bug will soon give up on it, but also am afraid it will start looking at the new growrh on my other trees. I treat them all with the sprays. I can't figure out where they are coming from as I don't see any ants nor what about it that attracts them to that particular tree. I have another Ponkan at the other end of the greenhouse and so far that is not attracting them. I think maybe that is because that tree gets a lot of air movement as it is nearer a fan. I keep suspecting my hibiscus may be the host as I usually keep them away from my other plants as they are notorious bug magnets, but even they seem bug free so far and not near this particular tree. Maybe they are in the soil of that particular tree, but I have even drenched the soil and I am still getting the black aphid or black fly back for now about 2 months. It is interesting to me that it likes that particular tree.

Cory