There are many possible answers. We really need to see a sample or at least a photo of the damage and a close-up photo of the needles, to see if it is a true pine (2, 3 or 5 needles per cluster), or a spruce or fir (single needles). What are the symptoms... brown spots, white spots, brown needles, do dead needles remain attached or fall off, is there sticky resin or not at the branch tips, is the tree in a low, wet area, are many needles still green but being chewed off, any insects or bagworms present, etc? Many questions I need answers to in order to make a diagnosis.
I will wait for a plant sample or some close-up photos to proceed, rather than going into all the possible options for all these different plants. Please send more info.