I am going to guess every day where and tear. My 2.5 year old tangerine from seed has something wrong with 80% of its leaves and is growing very well.

Is that damage still happening on new leaves? Is it past damage? Where do you live? Are those what you think are diseases in your area? How long has this been going on? Were your leaves at one point nice and green and then this? When did it start? Can you fill us in with more detail? Do you winter them inside? Did this happen while inside? Are they potted trees?

If the question was addressed to me, orange plant is in greenhouse in free soil, not potted plant, zone 6b in central Europe. These symptoms persist last four years and repeat every growing season. As you can see, brown lesions are visible on older leaves, on young leaves are only yellow areas, but not on whole leave. I dont think this is some chemical elements shortage or excess. This year were plants attacked by mites, maybe vector for plant infection....What do you think about agent - bacteria or virus? Please help me with identification. Thank you.

nobody have seen similiar symptoms on citrus plants? it cannot be something new to you.

Hi. To me it looks like past spider mite damage. But hopefully some experts will come by and help. I'm sure you'll get the help you need here)

You said "this year attacked by mites"....How do you know you had them? What did they look like? How did you treat them? Are you sure they are gone?

The set-up you have encourages mites like for sure.

Do you wet the leaves with cold water often? Do you use a fan for fresh air? Do you have vents? Does it get really get very hot, in there....?

The back of most of your leaves, the greyish light brown areas are damage that mites cause after sucking the leaves, and the brown spots are burn marks from the same areas they suck dry...
I am not going to make a true assumption, but what I can tell you is that that damage looks exactly like mite damage on other trees that I have seen up close...
I would make sure I am not looking at the same leaves over and over every year, make sure you are certain new leaves have a new problem..And I would treat for mites every month, since you are not putting your trees out..Have you ever thought of using natural preditors? I am assuming that you must have a pretty decent size greenhouse if you planted that one in the ground which would call for natural pest control..

Thank you for your comments guys. It can be spider mite damage on leaves, I was afraid of some bacteria or virus disease on it, mainly bacteria Xylella, which is invasive and fast spreading on several fruit species once occurs. Well, the orange plant is 4th year in soil, but still only 1,5 m high. And the greenhouse is about 3 m high, so enough space to grow yet :-) . I shouldav oid spider invasion by chemical treating or with predators use, not all together in one time. What makes me nervous, is that these lesions occurs every year on same plants, not all citrus plants in greenhouse are infected on leaves.

I'll bet if you stop spraying your trees with harsh chemicals, including strong pesticide and strong oils, and treated for mites on a 'regular' basis in a weaker dose more often, because those trees are stuck inside, you will get beautiful green leaves to please you)

The likely hood of you getting that disease you dread, is nil...You are not growing them in an area that has that disease outside, and likely someone that saw the importance of a disease like that would of stopped by by now and warned you..

Enjoy your trees and get rid of the mites once and for all, or at least get the upper hand)

Thank you for your advices mikerno, I will try to get rid of that unpleasent mites on my citrus plants. But it will take long period to say, that my citrus plants are free of pests :-)

Hi..) I don't think most people, especially those growing Citrus in a greenhouse will ever be able to know that their trees are COMPLETELY free of pests since some of them we can't even see with the naked eye, but we can all certainly get the upper hand in keeping them under control..Growing Citrus is not the way to go if one has a paronia about critters...)

looks just like the lesions on my potted lime and potted Meyer lemon. i found stick insects underside of some leaves, took them off and killed them but then just a day later same leaves had spots like yours. mine are three years old and I get flowers and small buds but never fruit as the buds drop off. ?? maybe something to do with these stick insects.