What a beech: Impacts of beech bark disease in Michigan from 2002 to 2012

Beech Bark Disease (BBD) has spread across much of the northern range of American Beech since its arrival in eastern Canada around 1890. The nonindigenous beech scale, Cryptococcus fagisuga Lind., colonizes the outer bark of beech trees, facilitating the entry of the cambium-killing Neonectria spp. pathogen. Infestations of beech scale were first identified in one Lower and one Upper Michigan County in 2000. In 2002-03, impact plots were established in 62 sites in 22 counties, representing stands that were uninfested, lightly infested, and heavily infested with beech scale. At that time, impacts of BBD were minimal and data represent pre-BBD conditions. In 2010-12, we revisited the 62 impact plots to quantify current beech scale densities, overstory condition, understory vegetation and down woody debris to assess effects of BBD on stand composition, productivity and wildlife-related variables since 2002. Scale densities since 2002, have increased across all infested locations and many originally uninfested sites are now infested. Beech scale has spread from the original discovery in two counties in 2000 to 27 counties to date. While species composition remained relatively unchanged, beech mortality in Upper Michigan beech scale infested sites, increased from 5.5% in 2002 to 25.5% in 2012 reaching as high as 77%. In Lower Michigan beech mortality is substantially lower, but still increased from 9.1% in 2002 to 10% in 2012, where all were < 24%, with one exception. In 2002 infested sites, beech mortality changed from 13.3% and 13.5% to 40.7% and 13% in Upper and Lower Michigan respectively.