I just put 4 citrus that had been in containers for 4 years in the ground and i started noticing sunburn! VERY SURPRISED, especially with my grapefruit since they love heat! Anyways, i just painted all of the trunks white as well. I've seen them painted white all my life so i figured it wouldn't hurt! I also painted some bare root pecans and peaches as well just while they acclimate. i don't know that i will do it once they are established.
I'm curious what others think as well.
Don't be surprised here.
Citrus are a closed canopy tree, meaning they prefer to shade their trunks. This is why pruning citrus is not a good idea other than for size control and removing dead, damaged or diseased limbs. If you open their bark up to direct sunlight, they will get sunburn.
When shopping for citrus trees, avoid the long bare sticks if you plan to plant in direct sunlight. If you do, leave it in the pot and keep it in filtered light until it closes its canopy.
The exact opposite is true for stonefruits, apples, pears, etc. They are open canopy, and prefer wind and sunlight reaching their inner canopy. The only thing you'd need to paint on a stonefruit would be possibly around the graft unions, otherwise they're not going to sunburn like a citrus would.