Several diseases and parasitic infestations cause untold damage to pinyon pines. Here are ways to help recognize and diagnose them.
Black Stain Root Disease (Leptographium wagneri)
Black Stain Root Disease kills sapwood. The disease spreads through grafting and root contact with diseased trees. Also, insects can carry the spores of this disease up into the vascular system of the trees. This disease also creates primary routes for damaging insects to follow, further damaging the trees.
Symptoms
- It is called black stain disease because infected sapwood of the tree and roots become stained black.
- There may be resin dripping down the trunk of the tree.
- The cones are abnormally small
- The needles turn yellow and then brown
Treatment
- You may try digging trenches between trees to prevent spread of the disease through root contact. However, this will only work if the trees on the opposite side of the ditch are free of the disease.
Dwarf Mistletoe (Arceuthobium divaricatum)
More of a parasite than a disease, dwarf mistletoe is tiny parasitic plants, without leaves but with flowers. They grow on branches and are genus specific. In other words, they will infect only other pinyons. They kill trees by robbing them of water and nutrients, and they do it very slowly. This parasite can be green, greenish-brown or yellow. The shoots from the plant can range from a half inch to six inches long.
Symptoms
- The needles are turning yellow
- There are dead branches near the crown of the tree
- There is swelling on the bark
Treatment
- Prune out lower branches that are infected. As soon as the branches are cut, the parasite dies.
- Remove trees that are seriously infested
- Plant other tree species as a buffer between trees that are infected and those that are healthy. The buffer zone should be at least 50 feet wide.
Armillary Root Disease (Armillary spp.)
This fungal disease usually infects trees that are already infected by insects or by other diseases, or are stressed by other factors. It spreads along roots by fungal structures.
Symptoms
- The needles become chlorotic
- The crown thins out
- There is a flow of resin or sap at the base of the tree.
- The cones are disfigured or undeveloped
- At the base of the tree, there is a yellow, stringy substance.
- Mushrooms developing at the tree base. These are golden or amber colored.
Treatment
- Remove trees that are infected.
- Plant species such as juniper that are resistant to the disease
- Improve the growing conditions for the trees.
- Remove infected species and plant resistant species such as juniper.
- Improving growing conditions. (This fungal disease does not do well in places that are very hot, very cold or very dry,)
Related articles that may be of interest:
Planting and Caring for Pinyon
