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You are here: NRS Home / Research Programs / Forest Disturbance Processes /Invasive Species / Hemlock Woolly Adelgid /Control and Management / Biological Control / Using Computer Models to Identify Vulnerabilities in the Adelgid Life-Cycle
Hemlock Woolly Adelgid

Using Computer Models to Identify Vulnerabilities in the Adelgid Life-Cycle

[image:] The Adelgid Life Cycle simulator uses a graphical interface, through which parameters for the model can be adjusted.

Research Issue

The development of effective biological controls for the management of invasive species is both expensive and time consuming.  By identifying vulnerable life-stages in the invasive species (in this case, the hemlock woolly adelgid, Adelges tsugae, HWA), the potential for developing effective by biological controls may be increased.

The hemlock woolly adelgid is an invasive species which threatens the sustainability of hemlock as a forest resource in eastern North America.  This insect has few known natural enemies and a complex life cycle.  By developing models of the life history of the insect, with connections to outside factors such as climate (which the adelgid is known to be sensitive to), we can build simulated populations of the adelgid and identify vulnerabilities in its life cycle where small impacts on the adelgids may lead to larger changes in the population densitiy.  In practice, this helps to identify the characteristics (such as the timing of feeding) what might suggest more effective biological controls.  Our research has led to the development of an Adelgid Life Cycle simulator (ALCs), which allows researchers to run simulated experiments using potential biological control agents.

In turn, this helps refine the search for biological control agents, by identifying some of the key characteristics of biological controls likely to be effective (such as targeting a specific life stage of the adelgid).


Our Research

Using a flow-model approach, we built a simulation in which the life histories of both the HWA and beetle species known to feed on the adelgid can be allowed to interact under a variety of temperatures.  This model, called the Adelgid Life Cycle simulator (ALCs) can be used to play “What-if” scenarios, and look for patterns in population dynamics (such as life history synchrony between the adelgid and the beetle) that may influence the efficacy of the predator.  Users are able to modify parameters including life stage and generation-specific adelgid mortality rates, life stage specific beetle mortality rates, adelgid reproduction rates, adelgid temperature sensitivity, beetle predation rates, and temperature cycles.  The simulation is available for download and is run using a freely available computer program.

Expected Outcomes

The ALCs provides a tool for researchers and land managers interested in: (1) evaluating the potential population dynamics for the HWA under varying temperatures, (2) identifying vulnerable life stages in the adelgid life history which may be exploited for the management and control of adelgid populations,  (3) evaluating potential interactions between the HWA and biological controls, and (4) identifying knowledge gaps in the understanding of the biology and ecology of both the biological controls, and the HWA.

Research Results

The ALCs is available as a free downloadable file.  The download include help files and examples/tutorials to familiarize the user with the model.  Use of the simulations has shown that efforts targeted toward the overwintering instars may have a large impact on adelgid populations, because the overwintering generation is both sensitive to temperature and the more fecund of the two generations.

Elkinton, J.S.; Trotter, R. T.; Paradis, A. F.  2011.  Simulations of Population Dynamics of Hemlock Woolly Adelgid and Potential Impact of Biological Control Agents in Implementation and Status of Biological Control of the Hemlock Woolly Adelgid.  FHTET-2011-04.

Trotter III, R. T.  2008.  Climate Matching: Implications for the management of HWA.  In: Onken, B.; Reardon, R., eds., Fourth symposium on hemlock woolly adelgid in the eastern United States. Hartford, CT. U. S. Department of Agriculture, Forest Service, Forest Health Enterprise Team: 141-146..

Trotter III, R. Talbot, Montgomery, Michael E. 2008.  Modeling environmentally driven life cycles for hemlock woolly adelgid and the biological control agent Scymnus sinuanodulus In: Gottschalk, Kurt W., ed. Proceedings, 18th U.S. Department of Agriculture interagency research forum on gypsy moth and other invasive species 2007; 2007 January 9-12; Annapolis, MD. Gen. Tech. Rep. NRS-P-28. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 80.

Research Participants

Principal Investigator

Research Partner

  • Michael Montgomery, Research Entomologist, U.S. Forest Service, Northern Research Station

Last Modified: 05/08/2015

About this Research Area
About Hemlock Woolly Adelgid
Biological Control
Featured Publication

Trotter III, R. Talbot, Montgomery, Michael E. 2008.  Modeling environmentally driven life cycles for hemlock woolly adelgid and the biological control agent Scymnus sinuanodulus In: Gottschalk, Kurt W., ed. Proceedings, 18th U.S. Department of Agriculture interagency research forum on gypsy moth and other invasive species 2007; 2007 January 9-12; Annapolis, MD. Gen. Tech. Rep. NRS-P-28. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 80.