I dont have an ID for the white stuff but I would remove it, It could be some sort of fungus or mold since it gets watered at night for 5 days. The best way to water citrus is only when they need it but not when they start to wilt.

Your mix seems to be a bit too water retentive. I see you have 50% peat and some sand, what else is in it. It sounds to me like it will hold too much water.
mike

Sean, I agree with Mike that your soil plus frequent watering is causing a decline in your tree's vigor, making it susceptible to desease. A lot of people in this forum have had trouble keeping trees in peat-based potting soils and have instead made their own bark-based soil mixes. If you want to keep your tree in a pot and water as frequently, you may want to consider this (do a search in this forum for '511' or 'gritty' mixes). Alternatively, since you live in So Cal, (if you're able) you could just plant your Meyer in the ground in an that gets 8-10 hrs of sun and it'll be perfectly happy there year-round.

That's not a fungus, it is an egg case, and can't remember what bug it is, but you'll want to remove it. I would also repot your tree. I would use a good Cactus Mix for us here in California. I use EB Stone's Cactus Mix, which works very well for me with my container plants. Never put sand in a container mix :-) I would also mulch it with small wood mulch chips to help retain enough moisture. And you need to fertilize this little guy. I would use Grow More Citrus Growers Blend. You can apply at the roots as well as a foliar spray. This is a great product, water soluble and good for container citrus. I use it for my in-ground citrus as a foliar app for micro-nutrients. Your little guy looks a little chlorotic to me. and lastly, never, ever let your citrus get sprinkled! That is death to citrus. They do NOT like their trunks and branches sprinkled. Instead, you'll want to give it a good soaking a couple of times a week. More if it's hot out. I would invest in a good moisture meter (they're inexpensive) and make sure your soil stays at 50% moisture. If it falls below that, water.

Patty S.

kinda reminds me of mantis egg sacs.

Thanks everyone for the responses.

@TimSF: I would love to have a place to plant this guy in the ground, but I live in Southern California and real estate is ridiculously expensive :( My thoughts were to have some nice fruit trees ready to go for when I actually do have a home of my own :)

@hoosierquilt: I think you are correct about the white flakes being egg cases of some sort. They are flakey and brittle where I would expect a mold to be more pervasive. I saw someone treating something that looked similar by using a q-tip soaked in rubbing alcohol. I will also purchase some cactus mix this weekend for the repot, and order a moisture meter (http://tinyurl.com/3mzopop) as well. I saw some other information suggesting that using the sprinklers was not a good idea, but wasn't sure why. I will go ahead and take this guy out of the line of fire from the sprinklers and do it myself as you suggest :)

Do you guys think that I would be okay to continue using the fertilizer that I already have? Also, looking forward after this tree hopefully turns around and begins to look healthy...given the pictures in the album, can anyone suggest a good pruning plan? Is this something I should be concerned about now, or in a few years?

Thanks again :)

Sean, you'll definitely want to heed Patty's advice since she is quite the expert on citrus growing in the Southern CA area; she's successfully grown a variety of citrus trees there (she also is in the same [Sunset] growing zone as you). If you can't immediately get the Grow More Citrus Grower's Blend she recommends, you can probably still use your fertilizer AS LONG AS it contains the appropriate micronutrients of Magnesium (Mg), Iron (Fe), and Calcium (Ca) that are essential for growing healthy/productive citrus. I've read that California water is especially alkaline, so you may also want to add 1 capful of white vinegar per gallon of water at each watering. This added acidity will aid in the tree being able to take up the micronutrients better.

In regard to pruning, I wouldn't do this yet. Your tree is much too small and it needs all those photosynthesizing leaves to make food for its growing roots and any new topgrowth. I say let it do its own thing for a few years, at least until it's a few feet tall. However, with that said, the only thing you'll want to prune are any new growths that appear BELOW the graftline - allowed to take off, these root stock sucker growths will sap the strength from the Meyer lemon part of your tree.

Sean, as long as your Vigoro has micronutrients, that's fine, but I would also hit it with a foliar application of Grow More Citrus Growers Blend. It is something you want in your "citrus arsenal" here in S. California. With all the heavy, cold rains we've experienced in the last 2 years, you're going to run into the same issue I have with citrus in the ground (my soil is mainly DG here in N. San Diego county near the coast): a leaching of micronutrients, especially magnesium. So, start with the Vigoro, but do make a foliar app with some micronutrients. You'll see the difference, promise :-) And Tim's right, no pruning for now. Wait until you obviously need to do some MINOR shaping. Remember, with citrus, pruning equals no fruit. Citrus produce fruit at the tips of their branches, so you're cutting off your next fruit crop when your prune! And Tim's advice about removing suckers is right on. Just break them off if they're soft. If they've hardened off, trim close to the rootstock. Our water isn't too alkaline here in San Diego county - about 7 to 7.6. Fine for citrus. But, for your little guy, acidifying the water with some vinegar and pouring it over the fertilizer may help prevent the micronutrients from getting locked out due to the alkalinity. You guy needs a bit of a rescue. Tim's advice is good. Once recovered, you probably won't need to acidify your water. You can also achieve this with your foliar application - acidifying the water you use to dissolve your Growers Blend in. When you pick up your moisture meter, pick up a decent pH meter (don't buy the cheapest one). It's worth having these in your gardening tools. I've had both my moisture meter and my pH meter for many years. Great tools to have!

Patty S.

I sure don't recognize the white stuff. It's not an egg CASE, per se, but perhaps an egg mass. At first, I thought it might be the egg mass of either the fall webworm or the fall armyworm, both caterpillar pests. But I don't think so, after inspecting your images. I sure wish that you had a good hand microscope and could do a little dissecting.

Be mindful that many, many people have found that home pH meters AND moisture meters to be notoriously 'iffy'. It would be a good idea to double check the moisture level the old fashioned way (with fingers or dowel).