The Future of Invasive Insects and Diseases in Southern Forests

Insect pest species such as emerald ash borer are already expanding rapidly, and threaten the ecological viability of their hosts in the South. Photo by Debbie Miller, U.S. Forest Service, courtesy of

The Southern Forest Futures Project (SFFP) started in 2008 as an effort to study and understand the various forces reshaping the forests across the 13 states of the Southeast. Chartered by the U.S. Forest Service Southern Region and Southern Research Station, along with the Southern Group of State Foresters, the project examines a variety of possible futures and how they might shape forests and their many ecosystems and values.

The goal of the SFFP chapter on insects and diseases is to project the behavior of insect and disease pests that are anticipated to affect forest resources over the next 50 years in relation to changing climate, human activity, and biological factors. The focus of the chapter is the 30 species of pest insects or fungal pathogens that cause diseases projected to be of future concern.

Key findings include:

  • Nonnative pest species have increasing impacts in the South regardless of climate change, patterns of land ownership, or changes in the composition of vegetation.
  • “New” nonnative invasive insects and diseases will have serious impacts on southern forests over the next 50 years. Some species such as emerald ash borer, laurel wilt, and thousand cankers disease are expanding rapidly; they threaten the ecological viability of their hosts throughout large areas of the South.
  • Given the trend in introductions of nonnative insect pests and plant pathogens over the last 100 years, we can expect additional introductions from foreign countries of previously undocumented pests (insects, fungal pathogens, plant parasitic nematodes, etc.) that will have serious consequences for some native forest plant species.
  • When host material for a given insect or disease is projected to increase over the next 50 years as a result of climate change or management choice, we can expect more pest activity. For example, more pine acreage enables more southern pine beetle damage. Conversely, if host material decreases, the overall impact of pests relying on that host material will likely decrease.
  • Very few indisputable projections can be made about the effects of climate change on native or naturalized pests. Although climate-change-induced host abundance is expected to increase the activity of some pests, others (such as spongy moth) may become less active with warmer temperatures despite relatively similar levels of host availability.
  • Under the influence of climate warming, host plants, pests and pest complexes are expected to migrate northward and to higher elevations. Because migration rates differ among the affected species, migrating plants are expected to form new associations, which will then affect the pests, their host populations, and the interactions among them. Unexpected pests very likely will become important, while some that are currently active will be less severe in their new habitats.
  • Although not expected to be a significant problem in the next 50 years, the migration of lower elevation plants to higher elevations could ultimately eliminate or at least severely restrict the host ranges of current high elevation plant associations. Pests that act on a restricted host base, such as the balsam woolly adelgid and butternut canker, could become far more significant ecologically in areas of relict host populations. 

Access the Southern Forest Futures Project Technical Report.

Access the Summary Report of the Southern Forest Futures Project.


Access the latest publications by SRS scientists.

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