Ginny,

Well it looks like there are a number of things going on with your tree.

First off the pictures of the leaves that have the squiggle marks on them are due to Citrus Leaf Miner. CLM are a common pest for citrus and can be treated with a mixture of Volk oil and Spinosad. The key is to start spraying before the infestation occurs. Search the form for CLM and you'll find many posts and advice.

Second, some of your leaves look like they exhibit salt burn from the browning tips. Try flushing the soil by giving it a very deep watering. In the long run this can be prevented by following proper watering practices. Some of the fruit appears to have split which can also be due to inconsistent watering. You don't say where you are from so I can't really offer much advice on what that schedule should be; but there are lots of resources on the internet describing good watering practices.

Third, the tree appears to have some nutrition issues. After you have flushed the soil pickup a good citrus fertilizer with micronutrients. Follow directions on the box but for a tree of your size it's going to be a lot.

Fourth and finally, some of the leaves look to have some sort of fungal infection. I'm no expert on this but I'm sure some other members of the forum will chime in on this.

Good luck!

As said above, and more.

Knowing where you live can help us. WHERE do you live? CA or AZ or TX or ?

The distorted fruits are due to citrus bud mite. Rather common in home-grown citrus but seldom needs treatment.

The tree doesn't "appear to have some nutrition issues." It HAS nutrition issues.
Probably due to soil pH at or above neutral, also because it's hemmed in by concrete and stucco.

Further, it receives both direct sunlight and reflected light & heat.

Does it receive pool splash? If so, that could complicate the soil & nutrition issues.

The black on the leaves is sooty mold which follows feeding by sap-sucking insects. Common on citrus are aphids, scale and whiteflies. Find out which critters are active and apply appropriate management.

Thank you both for your replies. I hope this is fixable... I live North of Los Angeles County just a tad, in the Thousand Oaks/Newbury Park area. I believe I'm in "Zone 10" - we rarely ever freeze, have some ocean influence but are inland enough that we're protected from overmuch fog and wind. Our area is generally very temperate, although this summer was the hottest one we've had in 40 years, so it was hard on all living creatures, plants, animals and myself included! I'm going to go to the nursery this weekend with a list of things I'll need to try to turn it around.

And I agree that the tree is not in a good location but there it is.....it gets terribly hot there in the summer compared to the rest of the yard; the temperature has been 100f in that area almost daily this miserable summer. Unfortunately, it DOES receive a lot of pool splash when there are a lot of children (and dogs) playing in the pool, or if I accidentally flood the pool when refilling. We will have to be more careful. Maybe I should get some quasi attractive sandbags ;) to try to divert it.

I have seen WhiteFlies elsewhere in the yard earlier this year, but not on the tree. I don't see aphids, either, so maybe it's just the Leaf Miner? Would you recommend trimming it, deleafing, and/or removing the fruit or would that traumatize it since it is so ill?

Your advice is very much appreciated; the tree used to have the BEST lemons I've ever had and I'd really love to turn it around.

Okay, all excellent advice from both cayden and always from Jean. Additional suggestions: You need to drop crotch prune your tree, as it's getting just too tall. Lemons are notorious for sending up these vigorous water sprouts, so take the tree down in height using drop crotch pruning. If you don't know how to do this, see if you can find a GOOD tree pruning specialist who knows how to do this correctly. Your tree's root system is going to be challenged due to all that concrete, so keep the size of your tree down. Plus, it makes it safer to pick your fruit. Next, you must minimize the pool splash. That chlorinated water is bad news for the roots. Get to a good quality garden center and buy a high quality citrus fertilizer (I would suggest GroMore Citrus & Avocado Food) and apply once a month until you see your tree starting to respond with new flush. Don't be surprised if you see the older leaves drop, that's fine, just look for new flush. Once you see new flush, you'll be able to cut back to fertilizing once every other month. Use at least the amount recommended for the size of your tree. Lemons are heavier feeders than other citrus due to their prolific fruiting tendencies. Treat for ants to keep out aphids. You can remove aphids if you see them in the spring on the tender new growth by hosing the tree off with a hard blast of water. We talk about CLM constantly on this list, so just search for CLM or Citrus Leafminer on this forum. I think I've posted about 6 times in the last week, so not worth re-posting the same info :-) Besides, too late to treat from CLM at this time, you're seeing the aftermath and not an active infestation. And frankly, I don't even treat my mature trees, and it really is more cosmetic with an older tree. Don't worry about whiteflies, I've never seen them bother citrus. Lastly, I'd get 2 to 4 bags of high quality compost, and mulch your poor tree, then top with some back to help retain moisture. Your tree needs nutrients. Composting every season will help with any soil pH issues, which really isn't an issue here for us in S. California. Our trees do just fine without an pH adjustments, as our soil pH isn't that high. However, that being said, your soil pH can get higher next to the foundation of your house, from lime leaching out from the concrete. I also see some snail damage, so put down some Sluggo around the base of the tree (safe for kids and pets, fatal for snails and slugs.) And, the fruit split is due to uneven watering during our really, really hot summer and fall.. Just pull off the split fruit, it will attract insects and infection.

Patty S

the CLM dmg seems minor, most of the deformities and bad tasting fruit comes from mites, mal nutrition, and the pool water.

Thanks again, everyone! Patti, I think I can manage "drop crotch pruning", although I didn't know the name. Is now a good time of year for that? What IS a lemon's season? It almost seems like a winter crop around So Cal.

We have a very good nursery nearby, so this weekend I'll go in and start the treatments, with the pruning and prep done before then.

I'll let you know how it goes. Your advice is very much appreciated. Getting a diagnosis of what was wrong is very helpful. I was half afraid it was some terrible disease no one had seen before but it's true I've ignored the tree and just assumed it would continue to bear great fruit. Oops.. :-)

Drop crotch pruning is a very specific method of pruning that always leaves an apical branch. You may suffer some loss of fruit next season, but with a lemon tree, that can be a good thing, lol!! I've included a link to Tom Del Hotal's exceptionally good presentation on how to correctly prune fruit trees. This is applicable to all fruit trees, including citrus. We are very fortunate here in S. California not to have anything to awfully terrible to deal with, with citrus. With the exception, of course, with Asian Citrus Psyllid and the constant threat of HLB hanging over our heads, especially for you up in Los Angeles County, where one incidence of HLB has been discovered due to someone grafting an illegally smuggled piece of infected budwood onto a neighbor's tree. We are praying we have caught this in time. So far, no further discoveries of HLB have been reported. So, follow our advice, and your lovely lemon tree should like very nice next year for you! Bring the tree down low enough so you can reach every piece of fruit with your hand. I have banned all ladders in my garden, and I'm rather "height challenged". You should never have to get up on a ladder to pick fruit. It is the number one cause of injuries in your yard.

Patty S. (RN)

Here is a link that might be useful: San Diego CRFG: Fruit Tree Pruning Basics

I fertilized today, bought new pruning shears, cut back a lot of branches and generally cleaned it up. I did notice White Flies fluttering around when I'd finished cutting! I hadn't seen them before. I'll spray it on Sat..

Thank you all again!
Ginny

Citrus is ALWAYS a winter crop. Mature trees will produce year round, but the heaviest flush is always winter.

The supermarkets' policy of raising prices in the winter is flat-out price gouging, pure and simple. Those of us who have citrus trees spend the winter months looking for people to give away the excess fruit to!