Review Ecological consequences of an exotic fungal disease in eastern U.S. hardwood forests Eric J. Holzmueller a, *, Shibu Jose b , Michael A. Jenkins c a Department of Forestry, Southern Illinois University, 1205 Lincoln Drive, Mail Code 4411, Carbondale, IL 62901, United States b Center for Agroforestry, School of Natural Resources, University of Missouri, 203 ABNR Bldg, Columbia, MO 65201, United States c Department of Forestry and Natural Resources, Purdue University, 715 West State Street, West Lafayette, IN 47907, United States Contents 1. Introduction .................................................................................................... 1347 2. Focal species ................................................................................................... 1348 3. Dogwood as a ‘‘calcium pump’’? .................................................................................... 1348 4. Dogwood impacts on associated flora................................................................................ 1350 5. Dogwood on forest fauna ......................................................................................... 1351 6. Management implications ......................................................................................... 1352 7. Conclusions .................................................................................................... 1352 Acknowledgements .............................................................................................. 1352 References ..................................................................................................... 1352 1. Introduction Over the past century, forests in North America have been subjected to an ever-expanding array of exotic insects and pathogens (Anagnostakis, 2001; Campbell and Sloan, 1977; Orwig and Foster, 1998). The increasing movement of plant material and other potential vectors suggests that the emergence of new infections and infestations will continue to increase in frequency (Peterson et al., 2004; Porland and McCullough, 2006; Rizzo et al., 2002). While the near elimination of species that have resulted from invasive insects and pathogens are staggering, adverse impacts are not limited to these focal species. Many focal species perform vital ecological roles that may not be assumed by the remaining members of the species pool. This reduction or loss of ecological function may create a cascading effect that ripples through ecosystems and across trophic levels (Loo, 2009). For instance, by transpiring year-around, eastern hemlock (Tsuga canadensis) trees play a unique ecohyrological role in otherwise deciduous dominated forests. Loss of eastern hemlock due to mortality from an exotic insect (hemlock woolly adelgid; Adelges tsugae) threatens to increase stream discharge and increase diurnal amplitude of streamflow (Ford and Vose, 2007). Forest Ecology and Management 259 (2010) 1347–1353 ARTICLE INFO Article history: Received 25 October 2009 Received in revised form 6 December 2009 Accepted 11 January 2010 Keywords: Anthracnose Biological invasion Cornus florida Calcium Flowering dogwood Forest health Prescribed fire ABSTRACT Exotic pests and pathogens can cause extensive mortality of native species resulting in cascading effects within an ecosystem. As ecosystems lose species to exotic enemies, ecosystem function may be disrupted if the ecological roles are not filled by the remaining species. To illustrate this concept, this paper examines the impacts of an exotic fungus (Discula dectructiva) on flowering dogwood (Cornus florida), historically a common understory tree species in eastern U.S. hardwood forests. Recent studies indicate that dogwood plays an important role in the health and ecological integrity of forest ecosystems throughout the eastern U.S. by increasing the availability of calcium in the biota-rich surface horizons of forest soils. However, Discula destructiva causes a disease, dogwood anthracnose, which can rapidly kill dogwood trees. This paper also illustrates how past fire has increased dogwood density and improved tree health in areas infected with anthracnose, suggesting that prescribed fire may offer a tool for land managers to maintain dogwood as a component in eastern U.S. hardwood forests by shifting the ‘‘ideal’’ disturbance regime of this previously fire-intolerant species. ß 2010 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +1 618 453 3708; fax: +1 618 453 7475. E-mail address: eholzmue@siu.edu (E.J. Holzmueller). Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco 0378-1127/$ – see front matter ß 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2010.01.014