The leaves are sunburned. Underwatering, reflective heat from decomposed granite/rocks, and heavy exposure to full blown Arizona sun makes citrus leaves fairly susceptible to this out here.

What AJBB said

Here's a handy reference for watering your citrus trees. I'd guess your tree canopies are about 8 feet across so they'll need about 80 gallons of water every 10 days in summer tapering to once every 3 - 4 weeks in winter.

Just follow the link below to the U of A publications on citrus (and other topics). There is also a handy table to show you how much fertilizer to use depending on tree size and product.

Good luck.

Here is a link that might be useful: Citrus tree information

yup, classic sunburn

I have a grapefruit on a east facing wall and it gets afternoon sun and reflected heat of the wall and it looks the same. Mine is only a couple of years old...hope will be OK once the summer is over.

I have a dwarf valencia that has done this every year. Last year I put a sheer curtain over it, but it still dropped all its little fruit. This year it is well shaded with a BIG sheer curtain. I'd like to have some fruit after all these years.
Any negatives to shading this way?

My apologies for hijacking this thread, but I'm brand new to this site, am having similar issues and am trying to get info on watering times/amounts.
We bought a 30 year old home in Spring of 2013. It came with 4 mature citrus trees. We knew one was a grapefruit but an arborist identified the others as possibly one tangelo, one tangerine, and one orange variety. The grapefruit had a fungal infection at the base and was treated with fungicide and also treated for termites last September. All trees were fertilized at that time. We had a windy rain storm around 3/1/14 and I came home to find my grapefruit tree on the ground. Over the next 6 hours, I picked every fruit off of it (it must have had 200-300 lbs easy). After that I cried like a baby. The 3 remaining citrus were fertilized in March. The fruit on all the trees is delicious with the tangelo producing the least, but still a large quantity of fruit.
After that, I turned my attention to taking care of the others. Each originally had 2 drippers at the base and had 2" gravel running up to the trunk. My husband and I cleared 14' diameter rings around each tree to the edge of each canopy. We went from 2 drippers at the base to 4 drippers at the canopy and added bark mulch up to about 6â away from the trunks. About 3 weeks ago, I noticed the trees looking awful compared to our neighbors'. Curling and yellowed leaves with lots of leaf drop. I thought maybe doubling the drippers had actually caused overwatering. So, I reduced it.
Previous = 4 drippers, 4gal/hr each x 1 hour = 16 gallons per tree, 3 times a week (48 gal/week)

Current = 4 drippers, 4gal/hr each x 30 min = 8 gallons per tree, 3 times a week (24 gal/week)

IâÂÂve given it a couple weeks and the trees still look awful. In the comment above, it says the trees should get 80 gallons every 10 days in summer. The U of A Irrigating Citrus Trees table says an orange tree with a 14â canopy should get watered 29.5 gal per day in July. Is this truly âÂÂper dayâ or âÂÂper wateringâÂÂ?
IâÂÂm really confused about how much to water our remaining trees and I am horrified at the thought of losing another 25+ year old citrus tree. The trees were watered less and only at the trunks last summer and managed to look better than they do now. This is my first citrus growing experience and I welcome any advice.

You are watering way too often! Plant roots need oxygen in order to process nutrients and too much water doesn't allow air to return to the soil.

The watering in the publication is given per day because depending on your soil type and the age of the tree the interval will vary. In Yuma where they have sandy soil watering is more frequent. Here where our soils have high clay watering once every 10 days to 2 weeks for mature trees in summer if fine.

Check out page 3 of the Irrigating Citrus publication to see the interval.

Here is a link that might be useful: Citrus care (watering, fertilizing, diseases, etc.)

Thank you aztreelvr!

So if I reduce watering to once every 10 days, I'm not really sure where to start with the quantity of watering, but I guess I can play around with it, check the soil, etc. The fun part will be trying to figure out how to separate my irrigation zones because I have other trees in the same zone as the citrus that have different needs.

Thanks again!

Just follow the table in the citrus watering publication. If your tree has a 14 foot wide canopy it will need approx 290 gallons every 10 days (29 gals / day x 10 days). If it is larger or smaller adjust accordingly. You can apply with drip emitters but you'll need lots of them. The cylindrical adjustable ones (that dispense little streams) put out at least 10 gals per hour - maybe more. So if you had 10 of them you'd need to water for almost 3 hours to apply 290 gallons.

You could also use the low tech method and let the hose run until the basin is full of water. A fully open hose applys about 8 gallons a minute so 35 - 40 minutes would apply close to 300 gallons. It's a good idea to use a 'diffuser' on the hose so the water doesn't erode the soil.

Hope this helps.

Thanks for your help aztreelvr.

We have one tree that is planted on flat ground. The other two are on a slope with half rings of pavers to catch (some)water running down the slope. 300 gallons seems really extreme. I gave one tree 80 gallons on Monday and saw improvement. I gave the second tree 80 gallons last night. In both cases, the basins overflowed into the surrounding landscape. I ordered a soil moisture reader that should arrive today so I'll keep an eye on it and then adjust the quantity and schedule as needed. I'll water the 3rd tree tonight, but have to swap to a longer hose to reach it. Overall, it will be more work to hand water, but I don't have a choice. Ideally, our irrigation system should have been set up to have the citrus in one zone and everything else in the other. I guess it is quite a project to re-do that, so I'll be handwatering at least for this summer. The extra work is worth it for happy trees and delicious fruit in the spring.

Thanks again for your exptertise.

If your tree has a 14 foot canopy, 300 gallons isn't extreme. Citrus like lots of water but they also like the soil to dry out a bit in between waterings. You need to apply enough water to soak down to three feet into the soil. This not only creates deep moisture that remains in the root zone for a long time, but pushes any accumulated salts down below the feeder roots. Salts (sodium, calcium, magnesium, etc.) can kill plants.

Because you have runoff, you could try the 'cycle and soak' method. In other words you apply your 80 gallons, wait an hour or so and apply another 80 gallons. Timers usually come with three start time settings that you can use.

To water my trees, I use the hose and let it trickle slowly overnight when temps are cooler. This lets the soil absorb without runoff. The next night I'll move the hose to the other side of the tree (and at the drip line) and apply again. If the tree is large, a third night might be needed. I don't really calculate how much water runs through the hose overnight - its more of a rule of thumb.

Best of luck.

take AZ tree lvr's advice. He's correct.

It doesn't help that our tap water is crappy, full of salts and alkalinity.