Leaves on apple tree turning yellowwhy?

I just got my first apple tree this spring. It's a multi-graft low chill variety, with Anna, Einsheimer and Dorsett Golden branches. It was looking great and putting on new growth until about a week ago, when we started getting some rain. (I had been giving it the periodic, maybe every-two-weeks deep soaking until then, as recommended by our top-notch nursery for new trees.) Now, some of the leaves are turning yellow. No pattern to the yellowing I can see, some are yellow on each of the different branches.

Anyone have any idea what's up with this? And is it something I should be doing anything about?

Thanks, all!
Jill

Here's a bit more of a close-up...

I should also mention I sprayed with a grub-icide about 3 weeks ago. This tree replaced an ash tree in the same hole, that had expired because grubs ate the roots down to nothing. When we planted this tree, we dug out the soil and checked and got rid of about 60 grubs--ick! Unfortunately, due to a variety of unexpected life-events, I didn't get around to spraying the grub-icide until now. Any chance that's what's causing the yellowing leaves?

Whoops, forgot to post close-up...

Your tree looks like it's already dropped a lot of leaves.

I don't know what is causing your yellow leaves but if it were my tree, I would get some EM1 and spray the tree with it. EM America is right there in Tucson. Sometimes heat can stress a young tree and cause leaf drop...goodness knows it is getting pretty hot here.

Ltilton, I don't remember it ever being particularly leafy, or seeing a bunch of fallen leaves around the yard; however, it's entirely possible I missed it. I did find a picture I took back in the spring when it first blossomed, that just shows activity towards the ends of the branches then as well. I don't know if that's significant?

Jayne, what's the scoop with EM1? What does it do, and how would it help?

http://www.emamerica.com/crops-and-soils

Read about EM here. I have been using it for several years to build my soil microherd. Perhaps you remember that last year I posted a picture of one of my Anna's. It was struggling with growth, it had weird leaf formation i.e. just on the tips and it just seemed sickly. It also had some bark splits. I sprayed it with EM-1 several times and this year it out produced its bigger sister. I sprayed everything in my yard as well and had a better crop of everything. EM-1 builds the soil actually enlivens it, so the soil feeds the plants.

So it's a general-health sort of thing, rather than a specific remedy? That might be a really good idea to look into--thanks for the link; I'll read more thoroughly when I've got a better chance. (Chaos reigns around here sometimes...)

Does this look, though, like something specific I should be addressing?

What kind of drainage does it have? Could it be waterlogged?

Hmmmm.... drainage could be a problem, I suppose. The hole it was planted in was a LOT bigger than its rootball, but the soil is pretty heavy. Is there any way I can check to see if that's the problem?

The reason I recommended EM-1 is according to Dave Owens, The Garden Guy, grubs are controlled with good soil culture. In addition, you applied a product ending with the letters 'cide' and it is always good to remediate with beneficial bacteria and microbes after applying that type of chemical especially when growing food. My young trees always struggled their first few years because of our dry heat. I would provide your tree some shade if you can. I hung a sheer curtain in front of my tangelo for two summers in order to get it established. I rigged up a PVC frame for it. Unless your tree receives a constant supply of water it is hard for me to imagine waterlogging in the desert especially with our temperatures well over 100 degrees right now. You might also take your picture to a nursery person you trust and ask them. Sometimes it is best to get advice from growers in your specific area.

Hi tucsonjill,
I have perhaps a similar problem with a few of my young eating apple trees and all of my Bechtel crabapples - random leaves distributed throughout the tree turn yellow and drop. I asked several local nurserymen who told me not to worry about it. I then thought to ask our local ag extn service, and they said the following:
Some preliminary research of your leaves leads us to Necrotic Leaf Spot.
Cause: A physiological problem that occurs when a cool, rainy period of 4 to 5 days precedes several hot, sunny days. A hormonal imbalance may be the reason. The disorder is restricted to 'Golden Delicious' and its sports.
Symptoms: Irregular necrotic blotches occur on mature leaves within 12 to 24 hours. The shape of the blotches is restricted by the larger leaf veins. Blotches may vary in number from one to six or more per leaf. Affected leaves generally turn yellow and drop within 4 to 7 days of symptom development. Leaf symptoms and defoliation occur in two to four waves during the growing season. Young, vigorously growing trees are less affected than older, slower growing trees.
Chemical control: Although this is not a fungal problem, some symptom relief has been obtained by using EBDC fungicides such as mancozeb during cover sprays. In most years, control is not needed.
Jill, I don't know if this is the issue you are seeing also, but thought i'd pass this info along.

Hmmm... interesting. I'm not sure if we get anything out here that qualifies as "cool" since we started getting 100 degree heat early in May, but maybe it's relative since we have had on-again-off-again out-of-season rains. I haven't had such good luck with our county extension, but maybe I should give them another try and see if they comeback with the same thing.

Thanks for the info, SnowlineRose!

And in the meantime, I should take some of those leaves to our local nursery, which has several people who know their stuff, and see what they say.

Thanks for the help, all!