Invasive Species

More than 400 species of non-native (aka alien or exotic) invasive forest insects and diseases are established in the United States. Some of these insects have become invasive, spreading rapidly and causing significant economic and ecological impacts to the nation's forest and urban trees. Northeastern and North Central cities have historically been “entry ports” for most invasive pests and continue in this dubious distinction. Because of this, Northern Research Station (NRS) entomologists and plant pathologists have a long history of research on the biology and ecology of non-native forest pests and also on methods for control and eradication. NRS scientists conduct research to understand tree diseases in order to develop management strategies and planning tools for achieving the goal of healthy woodlands, forest plantations, and urban landscapes.

Current research topics on invasive species include prediction and prevention, detection and monitoring, management and restoration. Specific insects currently being studied by NRS scientists include the Asian longhorned beetle (ALB), emerald ash borer (EAB), hemlock woolly adelgid (HWA), and gypsy moth (GM). Specific diseases caused by invasive pathogens include sudden oak death (SOD), white pine blister rust, butternut canker, red pine shoot blight, oak wilt, and armillaria root disease; beech bark disease is a combination of infestation by certain scale insects and infection with a fungus. Other, stress-related diseases such as oak and sugar maple declines are also being studied.

Selected Research Studies

Technical Innovations to Reduce Impacts of Invasive Species
Technology that is available to manage invasive species and increase productivity of short rotation woody crops (SRWC) is often too expensive, difficult to operate, cumbersome, and/or impractical. There is a need for technical innovations that help to achieve these objectives while meeting specific experimental needs.

Aspen FACE Experiment
The Aspen FACE (Free-Air Carbon Enrichment) Experiment is a multi-disciplinary study to assess the effects of increasing tropospheric ozone and carbon dioxide levels on the structure and function of northern forest ecosystems.

Tracing the movement of an invasive insect using stable isotopes
To better understand the response of insect populations to increasing environmental pollution, we are using stable isotope analysis to trace the movement of an invasive insect in mixed tree communities grown under different air quality conditions.

Asian longhorned beetle
The Asian longhorned beetle (ALB) arrived here as larvae boring in solid-wood packing material from China. The first beetles were detected in trees in several suburban towns on Long Island and in Brooklyn, Manhattan, and Chicago. Later, ALB were found in northern New Jersey, Toronto, and Sacramento, CA. These outbreaks have triggered major eradication efforts that included inspection of ALL trees in designated quarantine areas. ALB have also been detected as larvae in warehouses and are destroyed. In its native habitat in China, the ALB is a normal, relatively harmless member of the forest insect fauna but it has infested poplars and other plantation-grown trees that were made into packing and dunnage materials. Laws now require that all such materials be treated kill any insect larvae. NRS researchers are instrumental in researching the growth habits of the ALB in the Forest Service=s only mainland quarantine laboratory and also working on detection methods with cooperators at the Oak Ridge National Laboratories.

Emerald ash borer
The emerald ash borer (EAB), an exotic pest relatively new to North America, attacks and kills all ash species growing here. The EAB probably first entered Michigan at least 10 years ago, presumably in solid-wood packing materials from China. EAB has since been found in Ontario, Ohio, Indiana, and Illinois and has also traveled to Maryland and Virginia on infested nursery stock. At this point, the only eradication treatment is cutting down, chipping, and burning the trees. Because ash species were planted in many urban areas as replacements for the elms that were killed by Dutch elm disease, many of our streets and yards are once again sadly bare. About 15 million ash trees in urban and forested settings have been killed by the EAB. Quarantines in the United States and Canada restrict the movement of ash trees, logs, and firewood to prevent new introductions. NRS scientists have been in the forefront of research to understand the biology and ecology of the EAB and to develop methods for prevention of spread, trapping, detection, monitoring, and management.

Hemlock woolly adelgid
The hemlock woolly adelgid (HWA) is a tiny sap-sucking insect first noted in the eastern United States around 1950 on nursery stock in Richmond, Virginia. It spread slowly on ornamentals until it reached the forests of the Appalachian Mountains, where hemlocks are an important part of stream-side and moist shady ecosystems. When this happened, around the late 1980s, the spread rate took off and HWA is now recognized as a serious forest pest. It has now spread as far as the Smoky Mountains and southern Maine. A heavily infested hemlock usually dies within 5-7 years, unless treated by methods that are not practical for wildland trees. NRS entomologists and their cooperators are working to find natural enemies of the HWA (mostly lady beetles from China) and are also investigating host plant differences (hemlocks in Asia and the West Coast are not killed by HWA infestations).

Gypsy moth
Gypsy moth (GM) caterpillars have defoliated oak and mixed hardwood forests, spreading out from Boston, where they were accidentally introduced around 1869. Because the adult females are flightless, the line of advance moves annually only as far as the early-instar caterpillars can “parachute” in the wind or the eggs are moved around by human activities. The line now reaches from North Carolina to Michigan. As well as studying the basic biology of the GM, NRS scientists have developed most of the products and application techniques used in recent decades by the “Slow the Spread” Program: these include Bt (Bacillus thuringiensis, which infects GM) and two general-use biopesticides that are registered by the EPA: Gypchek (a nucleopolyhedrovirus product for GM) and Neochek-S (a related product for European pine sawfly). An improved virus-production method for possible industrial-scale use have been developed by other NRS scientists. Natural disease agents such as viruses, bacteria, fungi, and microsporidia are being tested on insect populations to develop strategies for enhancing their effectiveness in mitigating damage by pests.

Asian gypsy moth
The Asian gypsy moth, the females of which can fly and thus spread more rapidly, has been accidentally been brought to North America on ships and cargo from Eurasia, especially the Russian Far East. The behavior, biology, and damage potential of this pest have been studied in our quarantine facility to assist eradication efforts.

 

Sudden oak death

Oak ramorum blight (aka sudden oak death, or SOD) is a non-native fungal disease that is killing oaks and tanoaks in California and Oregon, as well as infesting a large number of shrub species but not killing them. Unfortunately, some of these shrubs (rhododendrons, mountain-laurels, pieris, and others) are grown horticulturally in this same area and they could vector the disease to the East Coast. Indeed, some incidents have already happened. NRS scientists who have been researching the rates and mode of spread of GM and HWA have applied their expertise to make risk rating maps for SOD. Oak species are major components of eastern and midwestern hardwood forests and the host shrubs mentioned earlier are common understory components.