Looks like aphid damage to me, king. This is the time of year we see them in S. Calif. and AZ. A strong blast of water, or water and a little dishwashing soap will wash them right off. I've included a very nice resource for you to share with your neighbor from the AZ Coop Extension Services.

Patty S.

Here is a link that might be useful: Univ. of Arizona Cooperative Extension: Diagnosing Citrus Problems

The bubbling damage looks just like symptoms of the Citrus Psyllid, a pest that is found in your state (among others). Psyllids are known for the blistering effect.

The discoloration is a problem, too. Perhaps by the psyllids, or another problem altogether.

king, I defer to rhizo's bug knowledge. I know the ACP can cause leaf distortion, and sooty mold, but was not aware that this bubbling or blistering damage is indicative of the ACP. I would STRONGLY urge you to have your friend call their local extension office to have the tree diagnosed. If it is the Asian Citrus Psyllid, I believe that they will treat it for free, and give your friend guidelines for treating all their citrus. They will also test the tree for Citrus Greening, which is extremely important to rule out. Please have your neighbor call their local extension office, and then send them this photo. Or you can have them contact Dr. Glenn Wright from the Cooperative Extension office at gwright@ag.arizona.edu directly. Any homeowner who suspects they have the ACP really must follow through to make sure their trees are also not infected with Citrus Greening (HLB).

Patty S.

Calling in some experts about this will also insure that the problem is diagnosed by someone who can look at it in person. We're flying by the seat of our pants here, so to speak, with only an image or two to go by and no background information at all.

Just wanted to add the caveat emptor... all the advice you get here... some from VERY knowledgeable folks, is FREE; we do it to try to help those who have suffered less. Proverb...Experience is the best teacher... much better and less painful, to learn from the experience of others. I have learned lots of lessons from experience and many have been painful and costly. Here at this forum I learn things that are painless and cost me nothing; in return I try to share some of my experiences with others.

Looks like the psyllid damage I had after Hurricane Ike brought the little buggers in Sept 08. I didn't know what it was for months. The freeze of Dec 09 got rid of them. It's just hard for a citrus grower to hope for that kind of freeze again.

Hey guys thanks for all the info and help! Its actually a friends tree in Johannesburg, South Africa - I was there for a few months, my internet was spotty hence the delayed reply. I've informed the owner and hopefully a local nursery or expert can help!

Bad on you, kingkongos... you sandbagged us. You might have gotten much different answers, if you told us the tree was in South Africa and not Phoenix. Personally, I have never seen exactly this kind of leaf damage on lemon leaves. It almost looks like some kind of fly sting damage that we sometimes get here in Central America in avocados.