Question
i am not sure what type of tree do i have, but at the beginning of spring the leaves started with a white powdery mildew and the leaves started to shrink and curl at the tips. also the tips became pointy and yellow. i have used several products but they don't seem to work. and new branch growth has a celery type appearance (flat branches not round)

Answer
Sounds like you are describing powdery mildew, a fungal disease of the foliage.  If the termperature is less than 90F you can try wettable sulfur powder.  It is mixed with water and sprayed onto the foliage.  Another mixture can be made at home.  Mix one tablespoon baking soda with one tablespoon of cooking oil and mix with a gallon of water.  Spray the tree often, say every 4-5 days for about 4 or 5 times.  Then sit back and see if plant health improves.  A fresh mixture of the baking soda needs to be made every time you use it.  Good Luck.