Answer: As evergreens, pines usually keep their needles for 2-3 years but then drop some of the oldest needles as they age and no longer benefit the tree. If the trees are healthy looking and putting out new growth, the needle drop is probably normal and natural. Pines can develop diseases and sometimes insect feeding will cause problems but generally the trees can overcome these attacks. Keep your pines well watered (one inch of water per week over the entire root zone) and they should be fine.
Best wishes with your landscape!
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