The Incidence of Dwarf Mistletoe in Minnesota Black Spruce Stands Detected by Operational Inventories

We surveyed black spruce stands within 0.5 miles of US Forest Service Forest Inventory and Analysis (FIA) plots and compared dwarf mistletoe status with that of the FIA and Minnesota Department of Natural Resources (DNR) forest inventories. Our results differed from FIA results in 3 of 16 stands with FIA plots, with FIA most often not recording dwarf mistletoe in infested stands. The infestation status of 140 of 202 surrounding stands was the same as recorded for the nearby FIA plot. Minnesota DNR forest inventory identified dwarf mistletoe in only 26 of 112 infested stands. Using only the most recent FIA plot data, 8% of FIA plots were recorded as infested. Considering an FIA plot to be infested if it was infested at any time in its history raises the percentage of infested FIA plots to 11%. Of the stands we surveyed, 112 of 202 (55%) were infested, but spatial autocorrelation may bias our sample. For the infested stands, dwarf mistletoe is projected to infest 20% of the stand area and reduce timber volume by at least 14% in the current rotation.