Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2010
Publication Date: 8/30/2010
Publication URL: http://ddr.nal.usda.gov/dspace/bitstream/10113/45071/1/IND44411419.pdf
Citation: Ulyshen, M.D., Duan, J.J., Bauer, L.S., Fraser, I. 2010. Suitability and accessibility of immature Agrilus planipennis (Coleoptera: Buprestidae) stages to Tetrastichus planipennisi (Hymenoptera: Eulophidae). Journal of Economic Entomology. 103(4):1080-1085. Interpretive Summary: The parasitic wasp, Tetrastichus planipennisi (Hymenoptera: Eulophidae) is one of three natural enemies from Asia currently being released in the United States to control the invasive emerald ash borer (EAB - Agrilus planipennis). The current protocol for rearing this species involves presenting adult wasps with artificially-infested ash sticks made by placing field-collected EAB larvae into shallow grooves beneath flaps of bark. In this study, we used both artificially-infested ash sticks and naturally-infested ash logs to test which EAB developmental stages (early vs later stages) are most suitable for rearing these wasps. The wasps parasitized all EAB stages except for pupae, but parasitized fewer prepupal stages in naturally-infested logs than in artificially-infested ash sticks. The number of wasp progeny produced was positively correlated with EAB host weight. Later stage (large) larvae yielded more wasp progeny than prepupae (the last larval stage) and early stage (smaller) larvae. This information is valuable for the current parasitoid rearing system for biological control of the emerald ash borer in the U.S.
Technical Abstract: Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae), a gregarious larval endoparasitoid, is one of three biocontrol agents from Asia currently being released in the United States to combat the invasive emerald ash borer (EAB), Agrilus planipennis Fairmaire. The current protocol for rearing T. planipennisi involves presenting the wasps with artificially-infested ash sticks made by placing field-collected larvae into shallow grooves beneath flaps of bark. While third- and fourth-instar larvae were readily accepted by T. planipennisi in these exposures, the suitability of younger or older developmental stages, which are often more readily available in the field, has not been tested. In this study, we used both artificially-infested ash sticks and naturally-infested ash logs to test which EAB developmental stages (second- to fourth- instars, J-larvae, prepupae, and pupae) are most suitable for rearing T. planipennisi. Tetrastichus planipennisi parasitized all stages except for pupae, but parasitized fewer J-larvae and prepupae in naturally-infested logs than in artificially-infested ash sticks. This is most likely due to the fact that, in naturally-infested ash logs, these stages are confined to pupal chambers excavated in the sapwood and may be largely beyond the reach of ovipositing T. planipennisi. The number of T. planipennisi progeny produced was positively correlated (logarithmic) with host weight, but this relationship was stronger when J-larvae and prepupae were excluded from the dataset. Fourth- instar larvae yielded the most parasitoid progeny, followed by, in about equal numbers, J-larvae, prepupae and third-instar larvae. Second-instar larvae yielded too few parasitoid progeny to benefit rearing efforts.