Sparse Pine Trees Bugs Or Blight
This tree does not look like a pine. It appears to be a white or atypical blue spruce.
I can only look at what is in the photo because I cannot see needles close-up under a microscope.
From what I can see, it looks very much like Rhizosphaera needlecast, a fungal disease. It only affects blue and white spruce. Diseases and insects are specific to certain trees. Rhizosphaera affects the oldest needles first... it starts closest to the trunk on the lowest branches and works itself up and out on the tree. Eventually, all that is left on some branches is the new growth and the rest of the branch either has brown needles or is bare. The following year, the green needles on the end of the branch die. The disease infects one year and kills the second.
If you looked at brown needles that were on the tree with a 10 X hand lens or magnifying glass, there would be small black, rounded fungal bodies sticking out of the needle pores called stomata. This can be on brown needles or green needles, depending on the time of year.
This disease is enabled by warm, humid air. It happens faster if the trees are stressed by drought or crowding.
This disease is almost impossible to control with fungicides. Trees must be sprayed with an appropriate fungicide every three to four weeks from budbreak until in the fall when the temperatures drop reliably below fifty degrees, day and night. The fungicide has to be replaced after each rain.
To be sure, you can send samples to the MSU Diagnostic Clinic. There is a charge and you need to send samples of dead needles still on the tree. Go to: www.pestid.msu.edu to download forms to fill out and to find out what to send them.
Will the spruce Rhizosphaera needlecast fungus spread easily to other spruce trees? Should I cut them down to stop the spread?
As I said, the only trees to get Rhizosphaera are blue spruce and white spruce... all blues and all whites. You can cut down the ones with problems, once you are sure that this is the probable. BUT... it probably will have little affect on the disease spreading. Every infected needle that is scattered about has the potential. Don't forget that the disease came from somewhere... and it can come back to your property from somewhere. It may not be the original place but many people have planted many white and blue spruces in the last 50 tears so there is no lack of potential hosts out there.