Bauer, Leah
Publications in VIVO

Bauer, Leah Research Entomologist



profile narrative

  • My current research is focused on key mortality factors regulating populations of the emerald ash borer (EAB) in North America, where this invasive beetle has killed millions of ash trees, and in its native range in northeastern Asia, where it is considered only a minor ash pest. A better understanding of the biology and population dynamics of EAB will facilitate the development of safe, long-term, and sustainable management strategies for this destructive, non-native pest in North America. These strategies include biological and microbial controls, which are management tools generally considered acceptable for management of insects in environmentally sensitive areas such as forests and riparian areas. Biological control of EAB will likely involve introducing EAB-specific natural enemies from Asia to EAB populations in North America. Microbial control of EAB will involve the development and use of microbial insecticides registered by the U.S. Environmental Protection Agency (EPA). Microbial insecticides formulated with the insect pathogen Bacillus thuringiensis (Bt) are applied aerially in North America to manage insect pests in forested and riparian areas such as gypsy moth. In collaborative studies with scientists at Michigan State University (MSU), we determined that few natural enemies attack EAB in Michigan. Expanded research in China , with scientists at the Chinese Academy of Forestry in Beijing, led to the discovery of several EAB populations where we are studying its natural enemy complex. During the course of this research in China, we discovered two new species of wasps that parasitize and kill EAB: Tetrastichus planipennisi (Eulophidae), a gregarious larval endoparasitoid, and Oobius agrili (Encyrtidae),a solitary parthenogenic egg parasitoid. In 2005, we completed a study on the population biology of these two parasitic wasps, which overlap in an ash forest in Jilin Province China and reduced EAB populations by 74%. We have also completed research on parasitoid biology, developed laboratory rearing and storage methods, and evaluated host specificity for both species in our quarantine laboratory. In 2007, we requested approval to release these parasitoids in selected Michigan field sites to evaluate establishment, monitor spread rates, and determine effects on EAB population dynamics and ash survival. We are also studying the potential use of insect pathogenic microorganisms for management of EAB. If host-specific entomopathogens are found infecting EAB from China, these may prove useful as biocontrol agents through inoculative release into EAB populations, resulting in population crash (epizootic) or decline (enzootic). We are also studying the potential use of BotaniGard?, a microbial insecticide formulated with the insect pathogenic fungus Beauveria bassiana GHA, for suppression of EAB populations. This research began in 2002 after discovering the importance of fungal entompathogens as natural enemies of EAB in Michigan. In 2006, expanded field trials were initiated in collaboration with scientists from USDA ARS and Cornell University from Ithaca, NY. Research on a Bacillus thuringiensis- based microbial insecticide (Bt), which will target adult EAB via aerial application, is currently in the developmental phase.

research interests

  • If biological control is approved in North America, I will continue studying parasitoid establishment, spread, and impact on EAB and ash. Foreign exploration in China continues as we search for entomopathogens and more parasitoids. Once a Bt-based insecticide is developed and registered against EAB adults, aerial field trials will be needed to evaluate its efficacy for EAB eradication, suppression, and slow the spread programs in North America.

importance of research

  • EAB was first discovered in southeastern Michigan in 2002 and likely arrived in infested wooden packing materials used for international trade with Asia. EAB may have gone undetected for at least a decade due to widespread ash decline throughout the eastern U.S. EAB has since been found killing ash trees in Ontario, Ohio, Indiana, Maryland, Virginia, and Illinois, and efforts to slow its spread are underway in some isolated infestations. Once established, however, managers have found that eradication is not possible due to rapid dispersal of adult beetles throughout forested areas with abundant ash; lack of detection and control methods; and lack of compliance with quarantine regulations designed to prevent human transport of EAB-infested firewood, logs, and nursery stock. USDA APHIS predicted the establishment of EAB nationally within urban landscapes will result in the loss of up to 30-90 million trees, equivalent to 2% total leaf area and valued at $20-60 billion. USDA FS estimated the costs of tree removal and replacement by local governments and homeowners over the next 25 years at $7 billion (present dollars). EAB is now well established in natural ecosystems in Lower Michigan and parts of Ohio and Indiana. At present, managers estimate EAB has killed ca. 20 million trees in Michigan, a fraction of the 800 million ash trees in Michigan timberlands. The impact of EAB on urban areas, ash resources, forest biodiversity, and climate in North America will be profound. Clearly, sustainable and environmentally acceptable methods to manage the EAB invasion are justified and needed.

HR job title



selected publications