Looks like spider mites; you won't see them without a good magnifying glass. A good wash outside or in the shower will go a long way to getting rid of them. My advice... lose the fertilizer spikes and replace with a good soluble citrus fertilizer applied 3-4 times per year according to the label. Your tree looks to be a little underfed; and unhealthy trees are more susceptible to spider mites. I would also get a good foliar fert. and give your tree an application of that about every 15 days; I like Bayer Bayfolan Forte; lots of container growers here use Foliage Pro... there are others. Your tree looks a bit leggy; I am guessing it gets less light than it would like.

Well, clearly it has been sprayed with something that has caused some strange markings on the leaves. I would send your photos to Four Winds Growers and ask them what they think it might be. I suspect it will be fine, and will not affect the health of your tree. But, worth finding out what may have caused the discolorations and markings. Very odd, it appears to be a chemical burn of some sort. Patty S.

That is a very nice looking tree. I have 3 tangerine trees, 2 Meyer lemon trees, a lemonade tree, a Meiwa kumquat tree and 2 seed grown Fukushu kumquat trees that are from seed. All of my trees are doing great but only my 2 fukushu trees look as good as your tree as pictured. You probably have nothing to worry about. Citrus trees aren't even close to perfect. enjoy your tree and may it grow well and produce.

The good news is that my plant is still alive. I’ve had so much trouble with it over the years, I can’t remember the resolution to this issue here. But generally speaking, I have used fungicide a couple times when I thought there was fungal issues and I have used espoma 2-2-2 fertilizer every month or two to keep feeding it nutrients. However, almost all problems I have had are related to soil moisture. It’s so easy for the soil moisture to get too high and then suddenly thr plant starts looking like it’s dying and that’s when I realize the roots are too wet and have started to rot. It’s such a fine line. This is critical especially this time of year when the temperatures drop and evaporation decreases. Managing soil moisture has been the most important item for keeping the plant healthy. Also, don’t underestimate the importance of giving it full sun. there has been a huge difference in plant health between giving it “decent“ sun that I thought was sufficient versus finding a spot where it gets a full day’s worth.