Hi everybody,
I have a 3-year-old Yuzu Lemon tree, which I keep on my balcony facing east. It gets some sunshine up till about noon. Lately, I have noticed white shadows on the leaves, which look like it's been splashed with dirty water. The air outside wasn't clean this summer, some construction was going on the neighbouring buildings, and I thought it might be from the cement dust, but when I washed the leaves, the white dirt shadow stayed on. Can you advise me what it could be? Maybe a lack od a vitamin or mineral? I give to it occasionally N, P, K flower fertilizer, and I think it has all the needed nutrients. Please see the photos and help me if you can; Thanks.

to NGA

A conversation I used to have with my mother in law:
Me: What is that?
Her: Its a Yuzu
Me: Is that a lemon?
Her: No, its a Yuzu

Its a Yuzu. Not a lemon in sight.

On to your question: The foliage discoloration suggests to me that your plant is lacking in some nutrient or another. Concrete is a base and citrus are acid loving plants. The dust could have altered the Ph of your potting soil thereby making the nutrients in your soil unavailable to your plant. Your tree needs some fertilizer that's acidic. Find some fertilizer specifically formulated for acid loving plants.

with Daisy. Go for some fertilizer that is specifically formulated for citrus if you can get it.

Also, I'd give it another try to clean the leaves. That chalky deposit on them is blocking their ability to absorb sunlight, and you're only giving it half a day's sun as it is.

I use a tsp. of mayonnaise whisked with a couple of tablespoons of warm water on my orchid leaves if they get hard water deposits on them. Put this concoction on a paper towel and rub it on the leaves then wipe them with another dry paper towel. The acid from the mayo will dissolve the deposits and the oil will shine up the leaves again. Don't use straight mayo! It will be too acidic and leave too much oil.

Along with the fertilizer i would give er some used coffee grounds. Good acid.
😎😎😎

it may also be lacking in iron? i always feed my citrus (grown in pots) yuzu, 2 lemons, an orange, bearass lime, and a kaffir lime, general plant food and chelated iron ( either in liquid or pelleted form).

by the way, yuzu makes the best ponzu sauce for fish, or used as a dipping sauce mixed w/somen sauce for sukiyaki.