There are a number of possibilities, but lately there has been a large number of Pinyon deaths attributed to two problems: Ips beetle infestation and Black Stain root disease.
Ips Beetle
The first evidence of attack by the Ips beetle is reddish or yellowish boring dust in bark crevices in the trunk. In addition, ½ inch "pitch tubes" or masses of pitch may be found sporadically on the trunk. Attacks usually begin after the arrival of warm weather in late spring. Infested trees will show a chlorotic, off-color appearance by mid-summer, and depending on the severity of the beetle attack, may die. As with Pinyon pitch mass borer, a preventive spray can be applied to deter future attacks. Carbaryl (Sevin) should be sprayed on entire tree in mid May and again in early August. Also, avoid pruning your trees during these months as the Ips beetle is attracted to the smell of cut pinyon wood. As always, when using chemical control agents, follow the label directions closely for best results.
Black Stain Root Disease (Verticicladiella wagnerii)
Primarily found in Pinyon Pine, symptoms of this disease are a general off-color, or chlorotic appearance of the needles. This decline may extend over a period of years, resulting in tree death. A brown to black colored stain will be found in the xylary tissue (directly under the bark), usually in the roots and root collar at ground level. Bark beetles are suspected carriers of this disease, however, from tree to tree it is known to move through root contact. A pattern of old trees, new dead trees, and sick trees surrounding the infection "center" is a common signal that this disease is present. Control alternatives include trenching around the fringe of the infected area to eliminate spread through root contacts, clearcutting diseased trees, including stump removal to prevent infection, or a combination of these two methods. An important note is that the outward symptoms do not commonly express themselves until months after the infection has occurred. Hence, careful searching and identification of the Black Stain disease in adjacent, seemingly healthy trees is necessary to eliminate the disease problem.
