Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2010
Publication Date: 2/1/2011
Citation: Ulyshen, M.D., Mankin, R.W., Chen, Y., Duan, J.J., Poland, T.M., Bauer, L.S. 2011. Role of emerald ash borer (Coleoptera: Buprestidae) larval vibrations in host-quality assessment by Tetrastichus planipennisi (Hymenoptera: Eulophidae). Journal of Economic Entomology. 104:81-86. Interpretive Summary: The emerald ash borer is an invasive pest of ornamental and timber trees. Scientists at Michigan State University, the ARS Center for Medical, Agricultural, and Veterinary Entomology, the ARS Beneficial Insects Introduction Research Unit, and the USDA Forest Service, Northern Research Station studied vibrations produced by emerald ash borer larvae in wood to determine if the vibrations were used as cues by parasitoids that are being used as biological control agents. A better understanding of the cues by which the parasitoids find their host pests can help develop improved methods of rearing the parasitoids and improved methods of distributing them to areas that contain the emerald ash borer pests. It was found that larger emerald ash borer larvae produce louder sounds on average, and that the parasitoids laid more eggs in larger larvae. Relatively more female parasitoids emerged from larger emerald ash borer larvae. These studies have improved our understanding of the parasitization process.
Technical Abstract: 1. The biological control agent, Tetrastichus planipennisi Yang, is a gregarious larval endoparasitoid of the emerald ash borer (EAB), an invasive phloem-feeding species responsible for recent, widespread mortality of ash (Fraxinus spp.) in North America. 2. Tetrastichus planipennisi is known to prefer late-instar EAB but the cues used to assess host size by this species and most other parasitoids of concealed hosts remain unknown. 3. Vibrations produced by host movement and feeding activities are known to be used by many parasitoids to locate hosts. We sought to test whether vibrations produced by feeding EAB vary with larval size and if there are any correlations between these cues and T. planipennisi progeny number and sex ratio. 4. The amplitudes and rates of 3-30-ms vibrational impulses produced by EAB larvae of various sizes were measured in the laboratory before presenting the larvae to T. planipennisi. 5. Impulse-rate did not vary with EAB size but vibration amplitude was significantly higher for large larvae than for small larvae. Tetrastichus planipennisi produced a significantly higher proportion of female offspring from large hosts than small hosts and was shown in previous work to produce more offspring overall from large hosts. There were no significant correlations, however, between the T. planipennisi progeny data and the EAB sound data. 6. Because vibration amplitude varied significantly with host size, we are unable to entirely reject the hypothesis that T. planipennisi and possibly other parasitoids of concealed hosts use vibrational cues to assess host quality, particularly given the low explanatory potential of other external cues. Internal chemical cues, however, may also be important.