Submitted to: USDA Interagency Research Forum on Invasive Species
Publication Type: Abstract Only
Publication Acceptance Date: 4/30/2010
Publication Date: N/A
Citation: N/A Interpretive Summary:
Technical Abstract: Tetrastichus planipennisi Yong, a gregarious koinobiont endoparasitoid, is one of three hymenopteran parasitoids being released in the U.S. for biological control of the emerald ash borer (Agrilus planipennis Fairmair, EAB), an invasive beetle from Asia causing mortality of the ash trees (Fraxinus spp.) in North America. One critical step in development of a successful biological control program is an efficient rearing method for each biological control agent. Here we report results from two experiments aimed at improving rearing methods for T. planipennisi. The first experiment sought to determine which developmental stages of EAB were most suitable or preferable to T. planipennisi using both naturally infested large ash logs and artificially infested small ash sticks. The second experiment sought to compare the fecundity of small vs. large T. planipennisi females. Findings from these experiments showed that T. planipennisi attacked significantly more 3rd and 4th instars than J-shaped larvae of EAB, and did not parasitize EAB pupae. More T. planipennisi offspring were produced from large hosts (4th instars) than small hosts (3rd instars or younger). While T. planipennisi parasitized J-shaped larvae and prepupae when artificially inserted beneath the bark in ash sticks, these were rarely parasitized in naturally-infested logs, likely because these stages are too deep within the sapwood to be reached by ovipositing females. In addition, small and large T. planipennisi were equally capable of parasitizing EAB larvae inserted into ash sticks (i.e., exhibiting similar parasitism rates), and small females produced fewer offspring than large females. However, the offspring of small females tended to be larger than those of large females. Consequently, small females are not without value to rearing programs.