Your mango tree seems to be suffering from a problem in the soil. It could be due to soggy wet soil conditions, space dry soil conditions, space or over fertilization with a salt based fertilizer. I suggest you contact your County extension office and ask for some free information on planting and carrying for mango trees in your area.
Your pine trees are not going to affect the soil and a negative way it is a good idea to rake up the needles but they also can be used as mulch around plants which is a good idea. Pines can affect other plants by shading them out. Fruit trees such as mango need lots of sun.
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