When I see leaves like that on my plants, it's either a sign of sun scorch, or salt/fertilizer burn.

If your water is full of salts (minerals) and you don't water deeply enough, they accumulate in the soil around the roots and cause leaf tip burn, especially when paired with synthetic fertilizers, which add even more salts to the soil.

It would help to know where you are located, and whether your avocado has been exposed to any chemicals (fertilizer, etc.) or if you have hard water.

Google "avocado salt burn images" and see if this is what you have.

Thanks for your comments. First my bad, I was having a duh moment when I posted this.....this is a Mango not an Avocado tree. Its 1 of two that I planted about a year ago...out of pots. The roots looked ok at the time of planting, nothing obvious to my untrained eyes. I am located on the island of Eleuthera in the Bahamas. This one is the only ne showing this kind of browning...the other is fine. I'm suspecting wind/salt burn since the only real diffrence between the two trees is the other one, which is about 30 ft away from this one is in a more sheltered spot from wind and any windborne salt from the ocean. It won't be any sort of chemical drift from anything....I don't use any weedkillers or stuff like that.

That could be the problem! I'm just curious -- are you watering them? If so, what is your source? I stayed on Exuma once, and we only had rainwater from a cistern, so the water was nice and soft (but full of scorpions😒). We had to buy our drinking/cooking water, though.

Haven't had to water since July fortunately since we have had plenty of rain. When I do water I alternate between my cistern rainwater and the government RO water.

Yes - I thought those looked more like mango leaves

At least we know your water is not the source of the problem, so it looks like the windborne salt is the issue. You could wash it off, but then the salt will end up in the soil... I think there's a Tropical Fruit forum here -- perhaps they have some ideas. Good luck!