MDA finds encouraging results using new detection method to find emerald ash borer

The Minnesota Department of Agriculture recently finished the first year of a three-year EAB and EAB biological control detection study.

In the study, known as branch sampling, 300 trees were selected in the original Minnesota EAB infestation area (the core infestation found in St. Paul in 2009) and a surrounding area up to four kilometers from the core. Two branches per tree were sampled. Scientists looked for EAB to understand the extent and severity of infestation. Twenty of the 300 trees sampled were found to be infested with emerald ash borer. Of those 20 trees, only one was outside of the core infestation.

“These preliminary results are significant in two ways,” said Geir Friisoe, MDA Plant Protection Division director. “First, we found fewer infested trees than we expected. Second, there were low numbers of EAB in the infested trees. This is likely due to the diligent efforts of St Paul, Minneapolis and others who have removed and destroyed infested trees, slowing the population growth of the beetle.”

The harvested branches were also examined for signs of stingless wasps that were released in the area to combat emerald ash borer. None were found at this time. However, most recoveries of stingless wasps in other states occurred at least two years after release. The first releases of stingless wasps in St. Paul and Minneapolis were in 2011.

Branch sampling is a new approach when it comes to searching for EAB. Other methods include visual assessment of ash trees and use of purple detection traps. Branch sampling is labor intensive and less practical on a larger scale than detection traps.

An interactive map of confirmed EAB infestations and stingless wasp release sites in Minnesota is available on the Minnesota Department of Agriculture’s website at http://gis.mda.state.mn.us/maps/eab.htm.

The MDA is conducting the branch sampling study with partners from the University of Minnesota, U.S. Forest Service, DNR, and the cities of St. Paul, Minneapolis, Lauderdale, Falcon Heights, and Roseville. The study is being funded by a grant from the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources.