James,
It's a fungus that makes the needles brown and will kill. Cool wet weather is the cause. I use Ortho Garden Disease Control. It has the right % of daconil (29%) to do the job. A copper fungicide will also work and make the needle look blue green. The daconil can make them look light green because it puts a lite white coating on then for a short time but that's what I have always used.

James,
I spray about every 30 days winter-spring to prvent it. In our climate that's Jan Feb March. Don't let it drip in the soil. I cover the pot and soil with plastic until dry. The little ones can be tipped on it's side so the drips don't fall in the pot.

Thanks Tim.
James