Dwarf mistletoe and white pine blister rust are two primary causes of concern for ecosystem health at Craters of the Moon National Monument. Both affect limber pine stands, which account for over 95 percent of the forested acres in the monument. Dwarf mistletoe ( Arceuthobium spp.) is a native infectious parasitic organism that establishes itself on hosts such as limber pine trees. In general, dwarf mistletoe reduces the vigor and growth of infected trees by appropriating water and nutrients, and disturbing the normal physiological processes of the tree. Heavy dwarf mistletoe infections increase the susceptibility of the trees to attacks by bark beetles and to system failure from environmental stresses. In some cases, they can kill the tree by slowly robbing it of food and water. Death occurs slowly in most cases and depends on the severity of infection and on the vigor and size of the tree. Dwarf mistletoe has a relatively long life cycle between infection and seed production (six to eight years), which allows for long-term disease management. Management and control efforts in the 1960's were unsuccessful and resulted in the removal of 6000 limber pine trees. Today, dwarf mistletoe is recognized as a natural parasitic organism that has been a part of the Craters of the Moon limber pine ecology for hundreds to thousands of years. It has become an issue of "which is worse, the disease or the cure?"
Another major cause for concern in the monument is white pine blister rust. White pine blister rust is caused by an exotic fungus, Cronartium ribicola . This organism was introduced from Europe in the early 20th Century, and has spread throughout the entire range of white pines in North America. The life cycle takes three to six years to complete and attacks five-needled pines and shrubs in the genus Ribes. On average, over a third of the limber pine in the northern Rocky Mountains have been killed by blister rust, and about 75 percent of the remaining live trees are infected with it. Blister rust incidence in limber pine stands extends into southwest Wyoming and central Idaho. Since blister rust is an introduced species, genetic resistance is limited and the mortality rate has been extremely high. However, some naturally resistant white pines have been found, and breeding programs have been established to increase the quantity and market availability of their seeds. Forest diseases tend to progress at a slow rate. With adequate research, early detection, and appropriate management techniques, their damage can be limited. Surveys as recent as 1999 have found no blister rust within Craters of the Moon National Monument. However, an infestation within limber pine stands here could potentially eliminate up to 90 percent of the trees. Such a decline would have dramatic consequences for many species of wildlife as well as the scenic qualities of the monument. Today, park ecologists are surveying limber pine stands at Craters of the Moon for the presence of white pine blister rust and the extent of dwarf mistletoe. Monitoring and research currently underway aims to enable resource managers to detect, monitor, manage, and hopefully eradicate white pine blister rust, should any evidence of it be found in limber pine stands here. Protection of the limber pine resource through early rust detection and immediate action is key to preserving the unique scenery and ecology of the park.