Invasive Species

June 2020

The introduction of non-native insects, plants and wildlife from one region to another, sometimes intentionally and sometimes accidentally, has been happening for millennia. Because one region’s benign forest insect can be another region’s catastrophic invasive species, Northern Research Station scientists and partners are finding ways to understand and control non-native pests and anticipate the next insect invasion. This month, we highlight a scientist, research, and a partnership that are helping reduce the economic and environmental impact of invasive species affecting forests here and overseas.

Environmental Education

Forestcast logo.Forestcast: Season 1 - Balance & Barrier, a special six-part podcast series on one of the most significant environmental threat to our forests, and the scientists studying and combating these threats.

Featured Scientist

Jenny Juzwik

USDA Forest Service Northern Research Station Research Plant Pathlogist Jenny Juzwik Jenny Juzwik examines a branch for oak wilt symptoms.Jennifer Juzwik, research plant pathologist in Saint Paul, Minnesota, had her career “a-ha” moment while working as a summer camp counselor. “Why not study plant pathology, instead of human pathology?“ she said, reflecting on her initial plans to attend medical school. Plant pathology combined her love of the outdoors, fascination with trees and insects, and the challenge of understanding the complex interactions of disease, host, and environment. That realization launched her on a career of discovering the how and why of tree diseases and finding solutions that protect forest health.

As part of the Northern Research Station’s Restoration and Conservation of Rural and Urban Forests research work unit, Juzwik’s current research spans diverse species and geography. She is unraveling the causes of thousand canker disease affecting eastern black walnut and rapid ohi’a death, which affects an iconic tree species in Hawaii. With colleagues at the University of Minnesota, she works on finding molecular techniques for accurate and rapid diagnosis of oak wilt. She also provides the plant pathology expertise for a project to detect oak wilt outbreaks on the landscape via remote sensing.

Comparing the effectiveness of various systemic fungicide treatments for forest and shade tree diseases and evaluating improved management techniques for controlling the below-ground spread of oak wilt are other components of her research portfolio. Her work with the USDA Animal and Plant Health Inspection Service is helping develop alternative techniques for preventing log exports from spreading invasive pathogens.

Juzwik likes to share her passion for research. “I enjoy mentoring undergraduate and graduate students so I can pass on my experience and approaches in forest pathology,” she said. “It can be very hands-on. I recently had an opportunity to demonstrate the value of a drawknife (a knife with a handle at each end of the blade), which is drawn toward the user in shaving a surface) to a post-doctoral associate in describing two new tree diseases.” She sees mentoring as an urgent task, given that the number of research plant pathologists in the Forest Service dropped from nearly 50 in 1980 to nine today.

Juzwik’s hobbies include camping, hiking, biking, and kayaking, as well as quilting, travel, and history.

More about Jennifer Juzwik >>

Featured Research

New Tools for Biosecurity – Asian Gypsy Moth

Asian gypsy moths laying egg masses near lights on a Russian vessel while in portThe military adage “Know thy enemy” works equally well as a strategy for combatting invasive insects. Northern Research Station (NRS) scientists recently supplied key knowledge that will improve efforts to slow or prevent the establishment of the Asian gypsy moth in North America.

Periodic outbreaks of Asian gypsy moth have occurred in the United States since the early 1990s, arriving primarily on ships and cargo. The most recent outbreak occurred in Washington state in 2019, affecting 1,311 acres of forest. These new arrivals are of particular concern to forest managers because the caterpillars eat a wider range of plant species than their European cousin, which was introduced to the United States in 1869. In addition, Asian gypsy moth females can fly, spreading populations more widely and rapidly.

NRS entomologist Melody Keena and ecologist Talbot Trotter, with colleagues at Pennsylvania State University and the USDA Animal and Plant Health Inspection Service, developed phenology models that can predict the timing of Asian gypsy moth flight at a broad range of international ports, pinpointing the time windows when female moths are most likely infest North American-bound ships and cargo. Keena and a Natural Resources Canada colleague also revised a model that predicts the development and hatch of North American gypsy moth eggs to help predict when and if Asian gypsy moth eggs laid on ships and cargo may develop and hatch. The information these models produce can help determine the optimal timing for applying eradication tools and measures.

Keena’s continuing research is generating good news. “We are finding that which host plant an Asian gypsy moth can use depends on which hosts it used at home,” she said.  “That means they might not be as devastating to North American conifers.”  As work continues, the models eventually can be used to look at where specific strains of Asian gypsy moth can develop and do well in North America. Such information will be vital in the on-going efforts to reduce the risk to North American forest health.

Learn more about Asian Gypsy moth phenology and potential distribution >>

Learn more about Asian Gypsy moth host utilization >>

Featured Partnership

Sharing Knowledge to Prepare European Forest Managers for a North American Wood Borer

Group photo of 2018 EPPO Expert Working Group. Photo credit: Xiaoyi Wang, CHINESE ACADEMY OF FORESTRY. Used with permission.International collaboration is not a new endeavor to the Forest Service. In fact, the Forest Service actively engages in scientific research on ecological and economic forest issues in more than 90 countries around the world. Likewise, working closely with international partners is not new to Northern Research Station (NRS) emeritus scientist Robert Haack. Haack spent nearly 30 years as a Research Entomologist with NRS, conducting scientific research across the United States and in multiple countries.

In 2018, the twolined chestnut borer (Agrilus bilineatus), a native beetle in North America commonly associated with oak and chestnut mortality, was discovered near Istanbul, Turkey. In eastern North America, this beetle is known to infest trees already weakened by a stress event, such as severe drought or defoliation. However, the discovery of this species in Europe raised alarm with the European and Mediterranean Plant Protection Organization (EPPO). The fear was that the potential lack of native tree resistance and/or lack of natural enemies could lead to this new non-native pest causing significant economic, environmental, and social impacts.

A call was made to Haack and he along with Northern Research Station scientist, Toby Petrice, launched into action. Haack and Petrice are globally recognized experts in twolined chestnut borer (TLCB) and have extensive experience researching the life cycles and management strategies of this beetle.

The EPPO asked Haack and Petrice to prepare a datasheet summarizing TLCB biology and management options to guide the drafting of a Pest Risk Analysis (PRA). The EPPO also asked Petrice to join a 9-person Expert Working Group for a meeting in Paris to develop the PRA for TLCB.

In September 2019, the final PRA was used to recommend regulating TLCB as a quarantine exotic insect within the EPPO region due to its high-risk potential for infesting oak and chestnut forest and ornamental trees.

“Exotic insect invasions are a problem shared by all countries making international collaboration essential for mitigating risks and reducing impacts” said Petrice. “We must work together and share the responsibility.”

“The participation of experts from non-EPPO Countries in PRAs, in particular Haack and Petrice contributions on TLCB, have been considered very beneficial” said EPPO Secretariat, Camille Picard. “Sharing experience on TLCB was a key element to assess the likelihood of entry, risk of spread, and impact for the EPPO region.”

By sharing their knowledge, Haack and Petrice helped EPPO make regulatory decisions based on sound science as Europeans now face an exotic insect that threatens their chestnut and oak forests.

Last updated: 05/28/2020