Edge density key to controlling gypsy moth spread

“Slowing the spread of the gypsy moth is a priority in forest management in the U.S.,” says Ottar Bjornstad, associate professor of entomology and biology, Penn State. “Understanding the underlying patterns in the spread of invasive species is important for successful management.”

The accidental release of the gypsy moth in 1869 in Massachusetts has led to an infestation covering more than 386,000 square miles of the U.S. Northeast. Native to Europe and Asia, gypsy moths are currently found from Maine to North Carolina and west into Wisconsin where they defoliate trees and occasionally, cause extensive damage to northern deciduous forests.

“We analyzed historical data on the spread of the gypsy moth in the U.S. and found that its invasion has been characterized by regular periods of rapid spread interspersed between periods of little expansion,” says Bjornstad. “This is the first identification of pulsed invasions for an invading species.”

Bjornstad; Derek M. Johnson, Department of Biology, University of Louisiana, and Andrew M. Liebhold and Patrick C. Tobin, U.S. Forest Service, used historical, county-level quarantine records as well as forest service data from more than 100,000 pheromone traps set along the expanding gypsy moth population front for their theoretical model. The pheromone trap data were collected from 1988 to 2004.

They used a theoretical model to show how an interaction between negative population growth at low densities – “the Allee effect” – and the existence of a few satellite seed colonies created by human transfer of the insects over long distances, explain the invasion pulses, the researchers explain today (Nov. 16) in Nature. The gypsy moth adult is flightless and usually only spreads a short distance beyond infestation boundaries. External colonies occur when moths hitch a ride on vehicles or other items relocated by people. Without an Allee effect, these colonies would establish, but because gypsy moths exhibit an Allee effect, the low populations are insufficient for establishment of permanent populations.

This is also true at the edges of the population area. If the population density is low, the Allee effect prevents growth across the boundaries. The model showed that no pulsed expansion exists for populations unaffected by the Allee effect. However, when the it is a factor, not only does pulsed expansion occur, but it mimics the historic pulses of the gypsy moth population from 1960 to 2002 found in the quarantine records.

Currently, the containment program for gypsy moths aims at controlling outbreaks outside the current population boundaries. The researchers suggest that “the invasion might also be slowed by suppressing outbreaks near the invasion front (within the populated area), to reduce the number of dispersers to below the donor threshold.” This would decrease edge populations and prevent the periodic surges of growth that expand the territory.

Other invading species may also exhibit pulsed spreading. If researchers can determine that the Allee effect is in place, than this same plan of containment might aid in controlling a variety of pests.

Media Contact

A'ndrea Elyse Messer EurekAlert!

More Information:

http://www.psu.edu

All latest news from the category: Ecology, The Environment and Conservation

This complex theme deals primarily with interactions between organisms and the environmental factors that impact them, but to a greater extent between individual inanimate environmental factors.

innovations-report offers informative reports and articles on topics such as climate protection, landscape conservation, ecological systems, wildlife and nature parks and ecosystem efficiency and balance.

Back to home

Comments (0)

Write a comment

Newest articles

Lighting up the future

New multidisciplinary research from the University of St Andrews could lead to more efficient televisions, computer screens and lighting. Researchers at the Organic Semiconductor Centre in the School of Physics and…

Researchers crack sugarcane’s complex genetic code

Sweet success: Scientists created a highly accurate reference genome for one of the most important modern crops and found a rare example of how genes confer disease resistance in plants….

Evolution of the most powerful ocean current on Earth

The Antarctic Circumpolar Current plays an important part in global overturning circulation, the exchange of heat and CO2 between the ocean and atmosphere, and the stability of Antarctica’s ice sheets….

Partners & Sponsors