[PaulF]

I understand that many pine trees have cycles of dropping needles and production of more or fewer cones. I think the needle cycle is about three years but I don't know the cone cycle.

Cones are the reproductive organs of a pine tree; some are male and some are female. Under certain conditions that put stress on a tree, it will not produce cones in a stressful year. That stress can be caused by temperature fluctuations or drought conditions or lots of other things. Maybe that is the cause. I'll bet next year will be gangbusters for cones.