It’s sounding like we AZ growers need to pass along a few tricks to our so. Cal brothers. In no particular order....50% ( min) shade cloth on the west side for at least the first summer ( maybe two depending on growth rate). Larger root mass= better survival rate, so I mostly plant 7 gal trees, minimum. IF you have good drainage, mangos can handle a lot of water. If not, they rot out during heatwaves when you water every two days. I do DEEP watering three or four times in the spring to encourage deep rooting.
I grow a variety of silica accumulating plants to use as mulch, Vetiver grass topping that list. I also spray a few times in the spring to make sure the plant accumulated enough silica to withstand the heat. I also have worked to develop a microclimate that provides shade and humidity. Fast growing trees that can be chopped down in a few years are a great way of accomplishing this (morniga, tipu, ash,jacaranda, etc).
Plants have to be in good shape by the time June hits. I will gladly sacrifice a little growth in the spring by not pushing fruiting too young in order to have a healthier tree with better caliper growth.
I dig planting holes a year in advance and provide a lot of drainage via gravel, stones, pumice, etc. mixed with my planting mix. This allows compensation for settling, as well as establishment of fungal populations which can help augment roots. I will also will plant in Fall and baby plants thru winter if they are slower growing varieties. That gives a bit more root mass by the time June hits the next year. I can more easily compensate for our cool temps than I can for our brutal, dry summers....Fast growers like LZ and Peach Cobbler always do better in our heat than slower varieties. Dig BIG planting holes so roots can spread as fast as possible.
As long as the trees are in good shape during heat, I continue to fertilize lightly with fish emulsion (50% of recommended rate). This seems to allow for rapid recovery once our temps cool a bit and humidity rises again. If not in good shape, focus on moisture management and just getting the tree to survive. Danger zone is >105 and/or winds. I ignore crispy leaves and any crisped new growth and focus on keeping soil moist, not soggy, and do a quick hand misting in the AM and evenings to provide some relief to the younger plants.
Finally, I find a bit of amino acids and maybe a little superthrive seems to help avoid the worst damage. Absolutely avoid strong fertilization during heat. Trying to help by adding too much ‘stuff’ to your regimen is counter productive.
I hope this helps people. We in AZ are in uncharted territory when it comes to growing mango, so I hope my observations can help others avoid the 10 years of mistakes I have made.