Question
We have several large ponderosa pine trees that are showing decline at the top of the tree. The needles have yellowed and browned out, what could be the cause of this decline?
We live in Northern California.

Answer
There are a couple of root diseases that will damage and kill the root system and the damage will show up as the foliage thinning and declining. Also there a re bark beetles that will attack pines that the needles will turn from green to red or brown. The root diseases are slow and the turning is gradual over months or years--the beetles are fast and the turning looks like it happened over night. Once a pine has been attacked by beetles there is not much that can be done for that tree but the adjacent ones should be sprayed with an insecticide called Onxy (spray the trunk as high up as possible.

IF there is still green foliage on the trees you can help the health of the tree. For the root diseases try fertilizing  the trees with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree. This will encourage root growth and should help the tree fight the disease.

I would suggest you call the Calif. State Forestry agency and ask one of their Foresters to take a look to determine if it is bark beetles or a root problem. Their number should be in the local phone book.