Location: Beneficial Insects Introduction Research2012 Annual Report
1a. Objectives (from AD-416):
This project seeks to reduce populations of EAB without adverse effects on the environment via biological control approaches relevant to the knowledge base of the target pest and its natural enemies, and has three objectives representing different aspects and/or stages of classical biological control research and development: 1: Explore for natural enemies (parasitoids) of EAB in its native range and evaluate their suitability for introduction. 1a - Explore for parasitoids of EAB in its native range. 1b - Evaluate the suitability of discovered parasitoid for introduction to North America for EAB control. 2: Evaluate impacts of extant (indigenous) and previously introduced parasitoids on populations of EAB, particularly in northeastern and/or Midwestern states. 3: Develop effective mass rearing technologies for hymenopteran parasitoids of EAB and other invasive pests. 3a - Determine the key life history parameters of the concerned parasitoid species. 3b - Determine the optimal host stage and host density (or host to parasitoid exposure ratio). 3c - Determine the optimal environmental conditions for adult parasitoid survival, oviposition, and progeny development.
1b. Approach (from AD-416):
We will conduct foreign exploration for parasitoids of EAB in its native range including the Far East region of Russia, Korea, and China. In each of the study areas, five to 10 sites will be selected for EAB parasitoid exploration covering a wide range of habitats including upland and riparian natural forests with Oriental Fraxinus spp. and plantations of both North American and Oriental Fraxinus spp. At each selected site, ash trees will be examined for signs of EAB infestation in late summer, fall, and/or spring. Ash trees exhibiting any signs of infestation will then be felled, and debarked for sampling different immature stages of EAB and associated parasitoids. Promising parasitoid species collected from the foreign exploration will then be tested in quarantine against a list of North American Native wood-boring beetles to determine their host specificity. After completing host range studies, we will develop an environmental impact assessment (EIA) of proposed releases of the promising parasitoids, which will be selected based on their efficacy against EAB in the native range (Asia) and host specificity against North American native (nontarget) wood boring beetles, and submit the EIA to USDA APHIS (or other regulatory authorities) for review and approval. Once the selected candidate species are cleared for release by Federal and State regulatory authorities, efforts will be directed towards field release and establishment along with development of mass-rearing technologies and impact assessment.
3. Progress Report:
EMERALD ASH BORER RESEARCH: Field surveys of both North American green ash and Oriental ashes were conducted in the Khabarovsk and Vladivostok regions of Russia to investigate the occurrence of emerald ash borer (EAB), Agrilus planipennis, and mortality factors affecting its immature stages. We found that EAB densities (larvae/m2 of sampled phloem area) were markedly higher on green ash (11.3 to 245) than on artificially stressed Oriental ash (2.2 – 59). Mortality of EAB larvae caused by woodpecker predation, host plant resistance and/or undetermined diseases and parasitism varied with date, site, and ash species. While we observed little (<1%) parasitism of EAB larvae in Khabarovsk, we discovered that three hymenopteran parasitoids (Spathius galinae, Atanycolus nigriventris and Tetrastichus planipennisi) were observed parasitizing 0 – 8.3% of EAB larvae on Oriental ash trees and 7.3 – 62.7% of those on green ash trees (primarily by S. galinae) in the Vladivostok area. In addition, 12 Oriental ash trees at a study site in China (Heilongjiang Province) has been selected and artificially girdled to attract EAB and its natural enemies for sampling next fall. Previous study sites in Michigan and Maryland have been continuously surveyed for evaluation of the three introduced parasitoids (S. agrili, T. planipennisi, and Oobius agrili). In addition, four new sites in Maryland have been established and large numbers of those parasitoids were released there. Our surveys showed that several hymenopteran parasitoids including the three introduced agents have become associated with EAB in Michigan. Among these parasitoids, T. planipennisi was the most abundant, accounting for >50% of all parasitoid individuals collected; low levels (1 – 5%) of parasitism of EAB larvae by this biocontrol agent were consistently detected at survey sites in both Michigan and Maryland. Separately, the native parasitoid, Atanycolus spp., was the second abundant group, resulting in 19% average parasitism rate of EAB larvae. Other native parasitoids were also found at various survey sites in Michigan or Maryland, but much less abundant than T. planipennisi and Atanycolus spp. Following the development of the host plant-based method to rear emerald ash borer larvae, we continued studying the life history and biology of the biocontrol agent (T. planipennisi) and determined the critical fitness values of its progeny. We discovered that offspring production and critical fitness parameters (body size and sex ratio) of T. planipennisi from parasitized EAB larvae are influenced by host plant substrate, host-parasitoid group size, and/or host to parasitoid ratio in the primary exposure assay. These findings have led to significant improvement to the current method for rearing T. planipennisi. QUARANTINE SERVICES: A total of 63 permitted consignments were received by the Quarantine Facility, consisting of 7995 pest specimens, and 7114 parasitoids in 3 different genera. A total of 9 outgoing shipments, 3311 pest specimens, and 1432 parasitoids in 2 genera. A total of 4 identification requests were submitted to the ARS Systematic Entomology Laboratory for determination.
1. Improved rearing methods for mass production of the introduced parasitic wasp as a biocontrol agent (T. planipennisi). The emerald ash borer (EAB) is an invasive pest that has killed millions of North American ash trees since its detection in 2002. The parasitic wasp is an important biocontrol agent attacking EAB larvae. ARS researchers at Newark, Delaware found that offspring production, body size, and female to male ratio can be significantly enhanced by using healthy emerald ash borer larvae reared with the tropical ash logs. This finding has been currently adopted by USDA APHIS Emerald Ash Borer Biocontrol Laboratory (Brighton, MI) for mass rearing of parasitic wasp for field releases against emerald ash borers in the United States.
Duan, J.J., Oppel, C.B., Ulyshen, M., Bauer, L., Lelito, J. 2011. Biology and life history of Tetrastichus planipennisi (Hymenoptera: Eulophidae), a larval endoparasitoid of the emerald ash borer (Coleoptera: Buprestidae). Florida Entomologist. 94(4):933-940.