In many parts of Montana, tree fertilizers are simply not needed. Avoid unnecessary fertilization because it can lead to other pest problems, winter damage, contamination of groundwater, overly rapid growth, and unnecessary expenses. Tree injections, in which fungicides are injected from pressurized capsules directly into the tree through small holes drilled in the bark have shown variable results. If the tree is particularly important or valuable you may wish to try tree injections. Tree injections should be done only by professional arborists who can show evidence they have received formal training in the technique.
Improper injections can cause irreparable damage.
Avoid annual injections because pockets of dead wood result each time injections are done, even when done correctly, and over time, the dead wood can coalesce. University of California. Oakland, CA 94608-1239. Pirone, P., J. Hartman, M. Sall, and T. Pirone. Tree Maintenance .