The visible symptoms of either can be almost identical. However, given your location I'd lean to the underwatering scenario.

You should be able to test by digging down alongside the rootball the full planting depth. If the soil is wet or soggy damp at that level, too much water. If it is dry, not enough. You want the soil to be just moist to the touch throughout that distance - not too dry and not too wet.

And make sure the rootball itself is fully hydrated. Often if this is dry at planting time, it will remain dry regardless of how much rain or irrigation might have occurred. The moisture will not transfer well between the two soil types.

Sorry to say but it is a really terrible time to plant a fully leafed out pear in a hot climate. And are you saying you haven’t watered it at all? Rain is not sufficient for a newly planted tree, even at a more propitious time of year. Plus it’s right up against a masonry wall which will be radiating heat day and night. All you can do now is absolutely deluge the soil with water regularly, erect some kind of shade, eg an umbrella, and cross your fingers.

It was planted by the nursery and they watered them througly by the time it got planted and I did hand water them every other day just to supplement on top of the irrigation schedule that I set to run every 3 days. I set it to get 5-6 gallon of water every 3 days from the irrigation line and so I’m thinking the water should be enough and its only a week after it being planted.

not having any issues with other citrus trees that being planted the same day.

"its only a week after it being planted."

Then it is probably just transplant shock, which is not uncommon for any kind of plant to experience in any location in the US at this time of year. As floral noted, it is just a very unadvised time of year to plant much of anything anywhere.

Trees will typically snap out of it and be fine the following season if given proper care. I'd still dig down to physically test the soil moisture level and then fine tune your watering regime to accommodate.

in my MI... i PLANT NOTHING IN AUGUST ... to try to do it in AZ is nuts..

review this link.. section one: https://sites.google.com/site/tnarboretum/Home/planting-a-tree-or-shrub

you tree is incredibly stressed ... water properly.. and hopefully it will live..

fert is not a response to stress ...

it might lose all its leaves if its really stressed ... most trees can releaf if this happens in spring ... but its not great if this happens in fall.. when it had to use up stored energy it would otherwise use next spring... to relaf now..

in fact.. it might not releaf until spring...

just water properly ... and pray

if this was done by a professional... well that means you have a warranty.. and they can replace it in spring if its dead ... pro's run by different rules...

please dont tell us.. it has hanging fruit on it???

ken

you said: I set it to get 5-6 gallon of water every 3 days from the irrigation line and so I’m thinking the water should be enough and its only a week after it being planted.

why do you believe thats true.. dig small holes.. 3 to 6 inches deep.... and find out.. IF THAT IS GOOD ENOUGH ... we.. the tree needs water at root depth.. not the surface ...

Thanks for all the suggestions. I’ll check deep to the root ball and see if it gets the water or not. Currently, it hasn’t bear any fruit yet but some flowering.

and yes, it it’s covered by warranty but I don’t want to rely on that if possible since they still going to charges some fee to deliver and replant the new one.

It had flowers? In August? That’s weird. Sounds as if it had a chequered life before you received it. In fact, I can see an embryo fruit, which is months out of sync.

I don’t know but it starts to cool down in AZ and we’re in monsoon season right now. It’s more like spring like temp right now and most of my flowering shrubs showing flowers right now.

Regardless of any nascent flowers or fruit that may be developing, the beginning of September is NOT the time you should be seeing them unless you live in the Southern hemisphere. It is completely out of whack seasonally and with the tree's genetics. Pears do not bear fruit in the middle of winter!