A DENDROCHRONOLOGICAL STUDY OF THE EFFECTS OF EMERALD ASH BORER

The Emerald Ash Borer is an invasive species from Asia that causes mortality in the Ash (Fraxinus) species of North America. The larvae form galleries in the phloem of trees as they feed, which disrupts the availability of nutrients and moisture. Adult beetles feed on Ash tree foliage, which causes further suppression of growth due to loss of photosynthetic potential. The Emerald Ash Borer was first detected on the campus of Indiana State University in Terre Haute, Indiana in 2012. This invader causes high mortality, so Indiana State University treated a portion of Ash trees on campus with a trunk-injected systematic insecticide in an attempt to prevent complete stand death. This study endeavors to assess the effectiveness of insecticide treatment and the extent to which Emerald Ash Borer has affected Ash trees on Indiana State University’s campus. Another focus was to assess whether we could detect when the insect arrived using the tree ring record.

Twenty Ash and twenty Oak (Quercus) trees were systematically sampled in locations with high Ash concentrations on Indiana State University’s campus to create comparative chronologies. Since Emerald Ash Borer only affects Ash trees, the Oak samples were used to create a control chronology. Three cross sections of Ash that perished due to the invasive species were also collected. The wood anatomy of these cross sections was analyzed for damage from the beetle. A climatological assessment was also conducted on both species. The chronologies correlated well with one another, signifying that they are both limited by the same factor. Palmer Drought Severity Index and precipitation amounts were strongly reflected in the chronologies. We concluded that the trees have not been affected for a long enough period for damage from the beetle to correlate clearly within the tree ring record. In the near future, this location will be tested again in order to evaluate if the beetles have caused suppression over a longer residence in the study area.