You might also need epsom salts, it's good for citrus with yellowish leaves.

I would vote for 5 and 1. Where are you? I agree about Epsom salts. I use 1 Tbs per tree 2 or 3 times a year. If you want to see my trees, see the link below. Unfortunately, I have given up on trying to grow avocados here, it is too hot, dry and windy.

P.

PS Here is a link to a useful calculator for amount of sulfur to use:

Calculator

Here is a link that might be useful: Citrus Trees

Located in Southern California. This is a Hass Avocado tree.

What is the basis for applying Epsom Salts -- is this to treat magnesium deficiency? We had our native clay soil tested several years ago and the results said 808 ppm for Magnesium which they rated as "very high". For that matter, Phosphorus, Calcium, Magnesium, and Potassium were all listed as "very high".

We also have a dwarf orange tree planted in the same soil type and it produces and looks like a champ every single year. I use the same citrus fertilizer for both trees.

So why would an orange tree do great but an avocado tree suffer so much given the same soil conditions?

First, I believe it is only iron that doesn't get absorbed in high pH soils; so you need to apply chelated iron. Second, citrus get over 80% of their nutrients from the first 18" of soil, while the avocado has a much deeper root structure and the deeper soils might be quite different from the topsoil.

At what point do I apply more chelated iron, if necessary?

Here are some photos taken today. As for the nasty looking leaves, the advice I was given was to use copper as a foliar spray because those are fungal or bacteria spots. I've done just that every year from about March through September but it never seems to control or cure the problem. Maybe I've been given bad advice on the leaf spots?

Anyway, as you'll see in the photos the leaves are not very green. The last photo shows a few leaves from last year that are much darker green. They greened up after I applied the chelated iron a couple weeks ago.

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Your avocado looks normal to me; the new growth is the perfect color. Later, when they get full size, the leaves should get darker and leathery.
Once per year, in early Spring should be enough for chelated iron. Older leaves tend to turn yellow and then fall off. I wouldn't stress about this tree.

I don't think this looks normal at all.

In past years, the new growth has been noticeably darker. And although it's a different variety, a relative has an avocado tree nearby and its leaves never have spots or turn yellow like ours do.

You might want to try the California Rare Fruit Growers site. We all have experience in citrus and your frustration level might be reduced. You may also want to try the California Gardening or the Tropical Fruits forums. Finally, you might be interested in "How Not to Kill Your Avocado Tree".

Best of luck.

P.

Here is a link that might be useful: California Rare Fruit Growers

I found this graphic showing various stages of iron deficiency in the Hass Avocado tree. My leaves seem to fall in the severe category.

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pdge's suggestion to check out the California Rare Fruit Growers site revealed something I did not know. According to
AVOCADO Fruit Facts, the leaves of Avocado trees "normally remain on the tree for 2 to 3 years."

That's interesting because our tree has been shedding all of its leaves annually in March or April.