Flight capacity of Tetrastichus planipennisi (Eulophidae), an introduced parasitoid of emerald ash borer Agrilus planipennis

The willingness and predisposition of a biological control agent to engage in flight influences its population spread and ability to locate hosts. Determining the dispersal capability of biological control agents is often difficult, however, especially during the early stages of a biological control program when densities of the biological control agent may be low. A classical biological control program was initiated shortly after the emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae), was confirmed as established in North America. Tetrastichus planipennisi (Hymenoptera: Eulophidae) is one of three Hymenopteran parasitoids that has since been released. However, this tiny, koinobiotic, gregarious ectoparasitoid can be difficult to sample in the field. To gain inference on the dispersal capability of T. planipennisi, we used 24 custom-built computer-monitored flight mills that are able to accommodate small insects. We studied flight patterns over 24-hour periods. We found that T. planipennisi is capable of single flights up to 3 km but mean flight distances were approximately 0.3 km. Tetrastichus planipennisi is not an exceptionally fast flier, with mean flight speeds of 0.13 m/s, or approximately 500 m/hr. Over 120 individual flights were recorded for multiple individuals in a 24-hour period. We hope that our results, which provide conservative information on the dispersal capability and flight patterns of T. planipennisi, will help optimize release guidelines and aid in projections of population spread in field settings.