cali41, I would suspect some sort of fungal infection, since you have had some more humid weather over the last few weeks with the monsoons pushing up from the gulf (I'm in S. Calif, so we're getting it, too.) I if you can carefully prune out some of the inner branches to allow for more air flow, without losing your fruit, that might help your tree not become a victim to fungal infections. I've included a like for you from your own AZ Coop Extension program on citrus issues below.

Patty s.

Here is a link that might be useful: AZ Coop Extension: Diagnosing Home Citrus Problems

If the limb is dead, or leaves miscolored to the end of the branch, it could be fungal and require pruning back to at least 12 inches below the infected limb; however, if there is haalthy new growth beyond the affected leaves, the cause is more likely nutritional... micronutrient deficiency... most common magnesium. Because of the strong new growth and the amount of fruit on the tree, the tree is essentially sucking the life out of the old leaves to use for making new ones. I have seen this condition on Meyers in the garden that are overproducing and growing at the same time. More of a well balanced fertilizer at least 3 times per year tends to solve the problem, but won't make these leaves green again. Magnesium sulfate also helps, as your AZ soil may be short of that nutrient (most common and cheapest form is Epsom Salts..spread a cupla cups around the dripline. Your tree looks to be pretty big and old, especially for an AZ garden tree...Good luck.

Thanks for the suggestions. I have given it organic fertilizer twice this year already (valentines day and memorial day) and my final application will be this weekend (labor day).

We had several hard freezes this past winter (down to 28-30 degrees for about 6 hours) I was initially thinking this is just freeze damage because I had read you wont see citrus tree freeze damage for months after the freeze.

The tree is pushing out new growth and the orange crop is not and large as last year, but still, the oranges are growing and maturing.

Any thoughts?

The key is if the "damaged" limbs have good new growth beyong the damaged area; if so, it is a nutrient issue; 28-30 for a few hours is usually not enough to seriously damage a large orange tree.. anyway, freeze damage looks different. "organic" fertilizers are often a bit weak; and you have to put a lot; and they may also be deficient in some of the key micronutrients important to citrus. Check the label; and a cupla cups of Epsom Salt won't hurt the tree anyway... same for your roses, if you have those.

Not so sure this is a nutrient deficiency, since just a few leaves appear to be affected. If it were a micronutrient deficiency, you would see a much more pervasive chlorotic appearance. Cali, are these affected leaves more in the interior of this very dense tree? If so, it could be some fungal infection, that may not be so much an issue. I would try to open up the canopy to get better air flow. Remove any crossing branches inside the canopy. And, I would make sure if you're getting hard freezes in your area, you might want to consider not applying any more fertilizer at this point, but instead, apply a micronutrient foliar spray, instead. If you give your tree a big shot of nitrogen, you're going to have tender new flush coming out in a month or two that may not survive your next frost. I would be more inclined to fertilize in February, April and July/early August. I'm thinking Labor Day may just be too late for your area, for your last application if you're getting these kinds of freezes. Just a thought.

Patty S.