I'm no expert but it almost looks like mineral deposits from hard water,
like what Jade leaves get? Hopefully one of the citrus experts will chime in.

Are all of the leaves effected or just some? Are the leaf shapes distorted? I know there is something called citrus borer, which I have seen in person and it doesn't look like that to me but I could absolutely be wrong. Here is what my Meyer's lemon leaves currently look like...

Look up the Tristeza citrus virus and check to see if your tree had any of the other symptoms described. Do you know if your tree was grafted?

Tristeza my ***. Think first at usual problems, like universal pets.

It's spider mites damage, and if not treated in time it will affect more leaves. To see the spiders: put the flashlight of the phone behind the leaf and look through it. You will see a few moving black dots.

Neem oil+dishwash soap 1%, 99%water. Protect the tree from direct sunlight after spraying for a few days. Repeat in 1 week.

Thanks for the comments everyone. I suspected Spider Mites too but I didn't want to bias opinions. I'll check for spider mites in more detail. So far I've been hosing the leaves down from time to time (I hear they don't like the water).

And to answer some of the previous questions, it only affects some of the leaves. I think it probably had a bit of a spider mite problem indoors over the winter. Right now the plant is outdoors. Coupled with the hosing down, I'm hoping the spider mites aren't really a problem right now. The newer leaves seem unaffected.

Anyone have tips on how to ward off spider mites indoors over the winter?

Thanks.

If it's just spider mites, you can just spray the undersides of the leaves with water every day for a few days and that should knock them down... no need to overreact with treatment. Neem and dish soap are not necessary.

You can spritz the undersides of the leaves once every week or two to ward them over the winter. They do hate water. It's what I do with my Hoya bella, basil and some other commonly affected plants. I'm new to citrus, so I'm glad the experts could help ;)

I had the same problem on some mineola leaves last winter/spring. It was spider mites.

I didn't use any treatment other than tilting the plant and spraying with a medium strength stream of water over the laundry room sink. Smaller plants I will turn sideways or upside down (while covering the soil with my hand and a cloth to avoid it spilling into the sink) and place the plant right under the faucet so the water runs over the undersides of the leaves. For more severe infestations I may have to do this a few times at weekly intervals but it always solves my problem.

Then you could use a good horticultural oil to get rid of them before you bring them inside for the winter. Not sure where you live but if you plan on bringing them inside, I would not just use water if you want to get rid of the problem all together. Water definitely keeps them at bay, although I have been spraying my brugmansia all summer with water and the infestation got so bad I had to use the oil to get rid of them once and for all. It was horrible. Water did not do it for my plant.

Mike,

Brugmansia is a weed in Guate; but we control the ants totally.... daily battle.

Off to Ohio tomorrow for 10 days including a side trip to Montreal to visit the wife's Sister.

I second hitting them with some HO before bringing them inside. Spraying with water will keep them at bay outside in the summer, but when they go inside where the plant wont get rained on and the humidity will be much lower the mites will start to thrive and will also spread to any other trees you have overwintering with the Meyer. The Meyers have a difficult enough time dealing with the change in environment without the mites so your best to get rid of them. Remember that just because you cant see them anymore does not mean they are gone.

John , have a safe and wonderful trip! Miss your pics