The data set is collected to evaluate if two parasitoids (Spathius galinae and Tetrastichus planipennisi), introduced for biocontrol of the invasive emerald ash borer (EAB), Agrilus planipennis, into North America have established niche-partitioning, co-existing populations following their sequential or simultaneous field releases to 12 hard-wood forests located in Midwest and Northeast regions of the United States. Ash trees of various sizes (large, pole-size and saplings) were debarked meter by meter in early spring of 2019 (Michigan sites) or fall of 2019 (Northeast states: Connecticut, Massachusetts and New York). Detailed data collection procedures can be found in the associated publication in Biological Control. Resources in this dataset:Resource Title: Niche partitioning and coexistence of parasitoids of the same feeding guild introduced for biological control of an invasive forest pest - Michigan data. File Name: Michigan 2019-EAB Parasitoid Niche Partition-Raw.csvResource Description: Michigan DatasetResource Software Recommended: JMP,url: https://www.JMP.com Resource Title: Niche partitioning and coexistence of parasitoids of the same feeding guild introduced for biological control of an invasive forest pest - Northeast states data. File Name: NE Dataset 2019-EAB Parasitoid Niche Partition-Raw.csvResource Description: Northeast States Data setResource Title: Niche partitioning and coexistence of parasitoids of the same feeding guild introduced for biological control of an invasive forest pest - Data Dictionary. File Name: Data Dictionary for Parasitoid niche partitioning study from Biological Control.docxResource Description: Data dictionary