History of the MPB
The current MPB outbreak in Montana began in the late 1990's. In 1997 and 1998 we began to see increases in the acres infested with MPB from the very low levels of the mid-1990's. For information, areas reported as detected in a year were attacked by MPB the preceding year. In 1996 and 1997 bark beetle populations were in decline, except for MPB in lodgepole pine in extreme west central Montana. This was mainly on portions of the Lolo and Flathead National Forests and surrounding lands. Mild temperatures during these two winters increased the survival of MPB. In addition to favorable weather, increasing area with susceptible lodgepole pine added to the population increase. MPB populations began increasing in Deer Lodge County and around Butte in 2001, in addition to tree mortality continuing in the vicinity of the Lolo and Flathead National Forests. By 2003, the outbreak was continuing to expand, however, in some stands it was declining because of the lack of susceptible trees. The occurrence of MPB in Whitebark pine began inreaasing in 2004 in the Big Belt Mountains, Centennial Mountains and Crazy Mountains, as well as in Yellowstone National Park. Small groups of MPB-caused mortality began showing up outside of Helena in 2005. In 2006 and 2007 fewer areas were observed because of fires and smoke. This caused smaller increases in the amount of MPB activity recorded although levels remained elevated. Generally, the same areas were being impacted these years, but there was decline in some of the most severely impacted areas. In 2008 we were able to substantially increase the amount of area surveyed over the past several years and the amount of MPB detected reflected that event. Areas of the Lolo and Deerlodge National Forests that had been experiencing high levels of mortality declined or remained the same as susceptible trees disappeared. Other areas, notable around Helena, western Deerlodge and Beaverhead National Forests, continued to increase. Mortality in whitebark pine also increased, particularly on the Gallatin, Helena, Lewis & Clark, and Beaverhead National Forests.
From 1998 to 2008, the total area recorded as having MPB activity in Montana is about 3.35 million acres. Many of these acres were recorded in multiple years, but are only included once in this estimate. Over 31 million trees of all species are estimated to have been attacked and killed during this period.
During an outbreak of MPB in the 1970-80's, there was a statewide peak in 1982 with over 2.1 million acres infested. This outbreak continued for another 8 to 10 years after this peak.
Every year forest insect and disease professionals in Montana fly over many of the forested areas to detect mortality and defoliation. The following maps provide information on the location of MPB activity that was detected during these surveys in recent years. This does not include all MPB activity since not all of the forested areas are observed each year. The presence of MPB in any area does not mean that all of the host trees in that area have been attacked.
More detailed maps from 2008 and previous years are available at Aerial Survey Maps.
Aerial Detection Survey Maps
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