Mugo Pine problem
Hello. I have 4 very large 32 year old mugo pines. over the years I believe I have had sawfly and/or pine tip moth issues which I have controlled. Several years ago (5 maybe?) the needles started partially browning in one area, an area facing SW. Slowly it seems to be spreading. They are in mostly sun, some afternoon shade. Could you help diagnose this? and what should I do? thank you. Gail Burns
Howard County Maryland
There are a few possibilities. We do not see any scale insects, but look for white scale covers on green needles. There is info on this scale on this page from our website: http://extension.umd.edu/hgic/armored-and-soft-scales-trees-and-shrubs
If you find no scale, it may be Diplodia tip blight, a fungal disease that commonly infects mugo pines. It causes dieback of older branches and often proceeds very slowly from lower to upper branches. It can take years. New growth of infected branches is stunted, needles turn brown, and terminal buds exude excessive resin. No cure is possible if the plants are infected at the base. If only tips are infected, all infected needles, twigs and cones should be pruned back to healthy tissue and prunings destroyed. Prune when branches are dry. A copper fungicide can be applied in very early spring when buds open and repeated twice at weekly intervals. Fertilize in early spring or fall.
Bear in mind that mugo pines are not exceptionally long-lived and yours are very old already for mugos.