Distribution and severity of beech bark disease on American beech (Fagus grandifolia) in the Wells Plot in northern lower Michigan

Abstract

American beech trees (Fagus grandifolia) are commonly infested by a beech scale insect (Cryptoccus fagisuga) and then infected by a fungus (either Nectria coccinea var. Faginata or Nectria galligena). This phenomenon is called beech bark disease and affects forest stands of trees in the eastern and midwestern United States. The Wells Plot is located in Pellston, Michigan and is a one hectare plot that has not been studied since beech bark disease became prevalent in the area. This study examines the distribution and severity of beech bark disease in the Wells Plot through the relationships between the disease and diameter-at-breast-height of trees, growth rate of trees, and clustering of beech trees. Correlation between severity and increasing size of trees was observed as well as slowed growth rate and increase severity. However, no significant relationship between clustering and spread of disease was observed.