The first recorded outbreak in the Black Hills occurred in the late 1890s. An estimated 10 million trees were killed during this outbreak. Approximately five outbreaks have occurred since that time though none has reached the same magnitude. The outbreak in the early 1970s resulted in the loss of more than 440,000 trees. The last outbreak occurred from 1988 to 1992 and resulted in the death of approximately 50,000 trees. Beetle populations are increasing and are expected to continue to increase during the next five years.