This might be the wrong forum. If so feel free to move.

Just wondering if anyone has seen this on their citrus leaves and could identify and perhaps suggest how to prevent.

Yellow spotted leaf top.

Leaf Top

Bottom of same leaf. Notice the brown / black patterns that seem to be making the yellow spots on the top of leaf.

Leaf Bottom

Thanks.

Bo, I do not know the cause. As you live in GA is the tree planted outside or is it in a container? = Millet

Looks like the wet humid weather we are having down here in the south. I wouldn't worry about it, just make sure if it is in a container it is well draining.

My inground Meyer gets strange leaf spots like that every winter but returns to normal every spring. With this over wet summer we are having it has some now as well, but meyers are meyers... They are always tempermental...

I see this problem some too, but have never been able to connect it with and insect or disease. The problem does not seem to show up on new flushes of growth, and does not seem to cause serious problems. Maybe Lazz is on to something about the heat and humidity, but it seems like I notice it more in the spring before the first flush of growth.

I have often thought that the discolored places on top of the leaf might be caused by thrips feeding on the bottom side. I am not convinced the two are connected. Maybe Dr. Manners has some answers.

Ned

I got to looking harder at the problem and came up with this link.

http://plantpathology.tamu.edu/Texlab/Fruit/citrus/citrus.asp

They show some pictures of a disease called greasy spot. Sure looks similiar to me. If it is it would explain why I don't see it on new growth in spring, because I used oil sprays to help control mites. Oil sprays are suppose to help with the problem.

Ned

I don't know for sure what it is. But I doubt that it's greasy spot, which has a very picky life cycle that I would expect not to be completable in Georgia, especially in a potted plant. Here in Florida, the disease is currently existing as saprophytic hyphae in the dead leaf litter on the ground, under the trees. As we get summer rains, spores splash upward, and air currents carry them into the tree. Those spores that land on the underside of a leaf will sprout and grow epiphytically (as "air plants"), on the outside of the leaf, for several weeks. I know of no other fungal disease of citrus which does that. In August or Sept., they find and enter stomates. Once in the entrance to the stomate, they form an appresorium -- kind of a "cork" to plug the stomate open, and to hang on against being washed off. Then a few weeks later, they form a vescicle -- a pumpkin-shaped blob in the air space just above the stomate. Then, October and November, they grow inside the leaf, among the cells, but never actually penetrating the cells. Eventually (November-December), the citrus leaf cells have a sort of allergic reaction to the fungus, and the cells begin to die, even though they were never penetrated. At that point (usually mid-November here), the bottom sides of the leaves begin to show yellowish spots. then about a month later, the top side begins to show matching yellow spots, and the underside develops the "used motor oil" look that gives the disease it's name. Leaves fall from the tree in December, January, or February, and begin rotting on the ground, restarting the life cycle. So at least here, July is the wrong time to be seeing the pale yellow spots you're seeing. And if it were greasy spot, the underside spotting should be far more advanced than the upper side.

I first thought of whitefly injury -- have the trees been severely infested, lately (and this would take a truly severe infestation)?

But more likely is as suggested above -- too much moisture. In that case, the problem is known as oedema (or just edema for the modernists). It doesn't quite look right to me, in that the top sides don't seem to be raised blisters??? Still, I don't have a better suggestion.

Very interesting Dr. Manners, thanks!

Ned

Millet: This is a container tree. I plan to move it inside to avoid frost in winter.

Dr. Manners: I don't expect it is greasy spot, or else it is such a feeble infestation that it's hard for me to identify it as such. The leaves started to show this condition directly after we had some rain. I normally water the tree once every 2-3 days depending on soil dampness and had just watered the tree the day before. I considered oedema after I read some weeks ago on this forum what you described in another post, but the damage to the leaves didn't seem to be bad enough. The yellow spots on top which are directly opposite the dotted patters under the leaf are not raised blisters that I can tell. As far as whitefly, I've not seen a single whitefly on the tree. I have inspected the tree daily since I have had it (month or so) and have only seen a few "cloudy plant bugs" trying to eat some blossoms. I think too much moisture is as good an answer as any.

Ned: The link was useful. I appreciate you sharing that.

Laaz: I'm pretty sure the container drains well. It has several large thumb sized holes in the bottom and my soil mix has a lot of pearlite(sic?). Although it doubt it drains nearly as well as a CHC mix. I keep the pot from sitting flush on the ground with some 1x1 blocks and when I water the tree it doesn't take but a couple minutes to see the water coming out the bottom. Is this sufficient?

All in all the tree seems to be in very good shape. It has a fragrant bloom open right now, and recently about a dozen blooms dropped away leaving very small lemons. These are along with the half dozen or so ping-pong ball sized lemons already growing.

Thanks for all the support.

ya know, my myer started getting splotchy at the end of the winter- i ran it to the bathroom and gave it a good flush through of water- it stopped getting any worse and got a new flush of leaves after that. I think they all colored back up once I started feeding again in the summer......

Oh! Another idea comes to mind. You didn't say what you've sprayed on those leaves in the recent past? This could be injury from some spray material, and if I had to guess, I'd say a micronutrient spray containing iron. Citrus trees should not be sprayed with foliar iron. Am I getting warm?

Malcolm

I decided to look at the leaves again. With the unaided eye it is very difficult to make out much but with my camera I'm able to take very magnified pictures. Below are a couple pictures. At this magnification I can easily see "between" my fingerprints of my fingers (although not in this cropped shot)... that is close.

By taking a picture from underneath the leaf, I was able to use the sunlight to shine through the leaf and show what appears to be a couple of tiny blisters, as aluded to by Dr. Manners. I have circled the two areas that show light areas with a darker area in the center. I believe the center is a blister. They are so very small that it is hard to tell actually what they are.

Under shot:

Under Shot

And turning the leaf over and taking a shot from above I have circled the same two spots. From this shot it is easier to make out they appear to be slightly puffy spots in the center of the speckles:

Top Shot

These don't provide me with any more insight. But perhaps the information is useful to you experts.

Well, not conclusive, but still likely edema.

I have the same problem very similar as pictures suggested with my Chandler pomello and Oroblanco this year and last year. They are pronounced after several days maybe weeks of rain. I thought they were fungal problem but I did not do anything about it. The leaves stayed on the tree until they were replaced by new growth of leaves. The trees did not seemed to be affected by this except for aesthetic value. All the leaves were not affected and did not seemed to be spreading.

Oedema occurs when roots take up water faster than it can be used by the plant or transpired through the leaves. Water pressure then builds up in the internal cells of the leaf causing them to enlarge and form tiny swollen blister­like areas. - Millet