The effect of bark thickness on host partitioning between Tetrastichus planipennisi (Hymen: Eulophidae) and Atanycolus spp. (Hymen: Braconidae), two parasitoids of emerald ash borer (Coleop: Buprestidae)

► Parasitoid ovipositor length limits bark thickness that can be penetrated. ► Tetrastichus planipennisi did not parasitize EAB in trees with bark thicker than 3.2 mm. ► Atanycolus spp. parasitized EAB in trees with bark up to 8.8 mm thick. ► T. planipennisi is unlikely to establish or be effective in medium to mature aged ash. ► T. planipennisi should be released in young or regenerating ash stands.