I am sorry for this delayed reply to your gardening question. We are transitioning to a new Q&A system and your question was unfortunately lost in the transition. I have discovered it now and hope this reply is not too late to be of help.
That sounds like a root related problem. Dry soil and even more likely soggy wet soil can stress and even kill roots resulting in needle drop and, if severe, plant death. It may also be that your tree is suffering from a needle blight. Fungicide sprays can be helpful in preventing such diseases, but when that species is planted in an area with frequent rainfall it is much more prone to such blights.
Thanks for the question. Please stop in again soon!
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