Some things to consider:

1) Perhaps under an oak is an inappropriate location. Some trees give off chemicals to dissuade encroachment from other plants.

2) Was this a well rooted tree, or a fresh air-layer? They would need different care.

3) Generally loss of leaves is due to lack of water, stress, inability to take up water, over-fertilization, overwatering, sudden change in climate, temperature, or humidity and the like.

4) Did it start showing problems before or after being fertilized?

5) Are you in an appropriate climate? Has the weather been unusal, erratic, or ?

I would suspect the fertilizer. How strong? I never fertilize a tree until its established and growing, and then only sparingly.

Thanks to those who replied. I have planted other fruit trees (all - including the lychee - are air-layered) in the same vicinity under the oak tree canopy. The other trees are doing well except for the lychee. I live in Tampa, so that should not be an issue with the weather. I water on alternating days, and the fertilizer I applied was recommended to be by the nursery itself. They told me to apply a tablespoon of fertilizer each month. The weather has been particulary dry, but I water frequently. My main concern is whether the tree is dead or not and whether I should keep watering the tree to see if it will sprout new leaves or is it dead and I should uproot it and plant a new one? Thanks for your feedback.

Sounds like the fertilizer is not an issue. You can scratch the bark with your fingernail and look for green underneath to see if its still alive.

Here's a guess for you: I have a friend who grows lychees on the big island of Hawaii, and he says that one of the things that favors their growth is the high humidity on the side of the island where he's located (the leeward side, I think). Usually, I'd think that Tampa was pretty humid, but if you say it's been very dry recently, it may be the lack of moisture in the air that's affecting the leaves, especially if the tree's been air layered, which would make it much more sensitive to water-transport problems. As an experiment, you might want to cover the tree in some kind of cloth that keeps in some of the moisture after you're watering. At very least, try spraying the leaves (what's left of them) with water.

I've heard that the leaves can fall off if you over water, but I donÂt know if thatÂs just for potted plants.

John

Mushroom Root rot could be the culprit. I've read that you should never plant lychees in soil where an oak tree once stood. The mushroom root rot will kill the lychee through its root system.

Congrats on your fruit garden the sheer joy of raising exotic fruit for a gardener is awesome. Now You said that you got your lychee from a nursery great job. And they told you what kind of fertilizer to use great. now what you did not get from them is the instructions on how to properly test, and bring the soil to the proper PH needed for growing that kind of fruit.

Having the wrong PH can starve your new tree and kill it!!!

http://www.google.com/url?sa=t&source=web&cd=1&sqi=2&ved=0CBcQFjAA&url=http%3A%2F%2Fchronicle.augusta.com%2Fcontent%2Fblog-post%2Fsandy-hodson%2F2009-01-09%2Fwrong-soil-ph-can-starve-your-plants&ei=8Hp-TfuAGoOVtgfG-82BDg&usg=AFQjCNE97L87_5Amd3XCkQrtPqOPrWpHOQ

Folow the link and buy a soil tester online or the nursery and correct your trees problem.