Umm, please post a link to the images.

Hi, here are some raw links... you may need to paste them into your browser. I was trying to figure out how to make nice inline images, or at least hyperlinks. Thanks for your willingness to help.

whole tree: http://tinypic.com/r/kn8rr/6
base of trunk: http://tinypic.com/r/2mxhduf/6
holes, possibly from borers, and "warts": http://tinypic.com/r/ohjpfp/6
foliage: http://tinypic.com/r/iyeyvr/6
orange from last crop: http://tinypic.com/r/v6i5w3/6

The scratches on the trunk were from probing it with a key. The bark was rotten in that area and flaked off with almost no force.

You can see some of the "warts" in the trunk photo as well, I'm not sure if they're normal or not.

Sorry about that, here are inline pictures.

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You have an old orange tree that appears to have been originally planted too deep, or that soil has been allowed to build up around the base. Perhaps because of this, at least part of the graft has failed and the top variety has rotted and partially died just above the graft line. That's where you have found the bark just falls away. But interestingly, I think a rootstock sucker has, either by chance or by some human intervention, re-grafted itself higher up (on the left side of the trunk photo). It is probably this that is now providing nutrients and sap flow to the top of the tree. If done deliberately this type of grafting is called 'inarching'.
My knowledge is from potted plants in the UK, so you should check with a local expert, but this is what you might need to do to try and reverse the decline.
1. Remove those two dead branch remains much closer to the trunk. One is an old large branch that has left a route for infection to enter, the other appears to be the dead top of the self-grafted rootstock.
2. Reduce the whole tree by about half. Prune every branch - it is too big to be supported by the poor trunk condition.
3. Remove the chickens, and break up the ground all around the tree as far as the drip-line from the pruned branches.
4. Provide a high nitrogen citrus fertiliser. Take advice on quantity, but it needs regular feeding and a considerable amount.
5. Water or irrigate the whole area in dry conditions - but not within a couple of feet of the base.

I'm not sure about the 'warts'. Look like some type of large scale insect - can you remove them by hand, or are they part of the tree?

Citrange, thank you for your advice.

What is the purpose for breaking up the soil, and how deep? The soil is clay with poor drainage.

The "warts" are hard and woody. With considerable effort I was able to break one off (I think I used a key and a surprising amount of force, it would be impossible with bare fingers). Underneath it seemed like healthy yellow inner bark. There was no evidence of an insect.

If the soil is hard and compacted, in dry conditions any water is likely to run off without penetrating the ground. If you apply fertiliser it is also likely to be washed away without reaching the roots.

I dont think thats a grafted tree. In LA there are many old trees that have been grown from seed or rooted cuttings. That tree looks OLD. Old citrus trees get "lumpy" at the base of the trunk for some reason. Also I would be careful with breaking up the soil as Citrus feeder roots are very shallow and you dont want to kill the tree by harming roots. Also, that canker type sore looks like an old injury that is possibly infected, it doesnt look too bad though. I have seen many old trees that have the same problem from an old weed whacker injury or from god knows what. You can spray copper on it but I dont know if anything can help. Your best bet is taking some samples to you county extension just to check and maybe bring them some pictures. I would give the tree a pruning by 1/3 this year but Im no expert in pruning citrus so maybe someone can chime in on when and how to prune?

I would agree with feeding the tree but dont chickens provide nitrogen fertilizer??..lol

Jack,

Your orange tree looks very much like the one I grew up with in SoCal. And I agree with you that the flavor is out of this world!

Yours doesn't look bad to me actually, but I suspect you could improve on your watering and feeding. If I were you, I'd first install a drip irrigation system around the drip-line of the tree and make sure the tree gets sufficient watering, especially during our very dry/drought summers!

Do contact your local Cooperative Extension (LA link below) on how much water is appropriate for your area (a call to the UC Riverside citrus researcher center might also be useful). They will also be able to suggest what commercial citrus fertilizers are appropriate and how much/frequently you should be adding to your tree - I suspect that with the size of your tree, it'll require POUNDS of fertilizer/yr(!) spread out probably in 3-4 applications. Remember that most old citrus trees decline and die due to insufficient feeding (I think you will need more than the N your chicken are providing, BTW, namely micronutrients that can best be provided by a citrus fert.).

Lastly, I would suggest a proper trimming by an arborist specially trained to trim citrus. A proper haircut should rejuvenate your tree and decrease the canopy for easier harvesting of the fruit.

If you're lucky, Patty (hoosierquilt) who hails from SoCal will be by shortly to give you her invaluable opinion on your tree. As I recall, she is trained as a Master Gardener and frequently attends lectures given by the citrus experts at UCR.

Cheers,
Tim

Here is a link that might be useful: University of California Cooperative Extension help

You've gotten good advice so far, but my biggest concern is in the 3rd photo. You mention "boring insect" damage. I am concerned about what I'm seeing there in the 3rd photo down. Is this the boring damage you're referring to? If so, it could be termites. Those are our "borers" in California. They can get into damaged, dead wood if it is left on the tree, and eventually kill a tree. I just watched one of my neighbors lose a lovely Oro Blanco that was at least 15 years old because of string cutter damage to the bottom of the trunk. It left a wound where termites were able to get into, and they eventually killed the tree. So, have a pest control person come out if this is what I'm seeing. And, follow Citrange's recommendations for getting things cleared away from the drip zone of your tree, get the watering fixed, a well created at the drip line (edge of the tree canopy), get the drips set in the well, and fertilize every month until October. Cut away any dead wood down to healthy wood. Remove crossing branches. Bring down those top branches - way, way too tall a tree. You're going to end up with fruit much to high to pick.

Patty S.

Thanks for the solid advice so far.

I sawed a few inches off of the branch nub in the third picture, and it was crawling with ants inside. Large carpenter ants, with egg sacks and all. (The chickens gathered underneath as ants dropped down.)

I'm continuing pruning / feeding / watering. How would you recommend treating the ants?

Is your orange tree in the shade?

It kind of looks like some kind of front yard tree is in one of the first photos. Seems like a lot of shade on the old tree (might be why all the leaves are up high where they can find some light)

Use a broom or something to get as many out as possible and let the chickens eat them. For the remainders you can try to kill them with some kind of smashing utensil. I really dont know. Maybe someone else around here has dealt with them in fruit trees before? At worst you might need a chemical.

Spectracide triazicide concentrate (once and done) says that it will not kill carpenter ants so you might have to use something else. Ive always used industrial strength spray to kill carpenter ants for homeowners but that was when I had my license and was able to get the stuff but for fruit trees I really dont know how to get rid of them.

I found this forum while looking for information about citrus trees. I have a tree that might be thirty years old or more. It is on the property line and the neighbors insist that we cut it down. I am the only one who waters it. It was damaged in 2014 summer due to lack of irrigation as I was out of the country. Now half is dead. I thought that I would use the dead branch for a lady banks rose as the tree is above a spot where we sit. We recently had a termite guy for the wood in the brick patio and he confirmed that the dead part of the tree had a colony of termite. He suggested that we cut the dead part. That it would help the rest of the tree. My question is, will it really help? And whom should I ask? I live in Claremont, CA.