The moth Lymantria dispar asiatica (adult female shown here) has been unintentionally introduced to North America several times in the last few decades. Through a complex monitoring and management program, officials have been able to prevent this pest from establishing in North American forests. A new report in the open-access Journal of Integrated Pest Management gives an inside look at this success. (Photo by John Ghent, Bugwood.org)

By David Coyle, Ph.D.

David Coyle, Ph.D.

Unless you’re intimately involved with invasive species research, education, monitoring, or regulation, you probably don’t know how many pest interceptions happen each week at ports around North America. Spoiler alert: It’s a lot. Insects, plants, vertebrates—all of these can be invasive species, and various federal, state, and local entities work tirelessly to keep our borders safe from pests that could do irreparable harm to our agriculture and natural resources.

Of course, with the destruction that has accompanied several high-profile invasive species, including the emerald ash borer and spotted lanternfly, one might think that our efforts are for naught. In fact, this couldn’t be more wrong. It’s true that a small number of pests occasionally slip by, but the bigger picture is that we’re doing a very good job keeping our agricultural and natural resources safe.

Invasive forest pests are, in my opinion, some of the most difficult to manage. They can infest trees that are basically in the middle of nowhere, where people may not physically visit for years. This differs greatly from agricultural pests, which are often found sooner rather than later because of the annual turnover of crops. Forest pests, meanwhile, can build populations in remote areas before they’re finally found, and even then effective control in these remote areas is challenging. As such, prevention really is the best medicine for these invasive species.

A new paper in the open-access Journal of Integrated Pest Management details one such a program from its inception—a program that deals with an invasive moth species, Lymantria dispar asiatica (LDA)*. Think of LDA as a more aggressive cousin of Lymantria dispar dispar (LDD). While LDD is firmly established throughout much of eastern North America, LDA is not yet established on this continent. Both species are very polyphagous, able to feed and develop on hundreds of host plants. However, LDD females do not fly, while LDA females are strong fliers, making this species even more concerning than its European relative.

Lymantria dispar asiatica moths gather on a building in the port area of Olga, Primorsky Krai, Russia. In response to the possibility of LDA moths riding on ships bound for North America, a complex monitoring and management program run by officials in both Russia and North America has been able to prevent this pest from establishing in North American forests. (Image originally published in Mastro et al 2021, Journal of Integrated Pest Management)

A ship docked in Nakhodka, Russia, shows egg masses of Lymantria dispar asiatica moths on its hull and superstructure. In response to the possibility of LDA moths riding on ships bound for North America, a complex monitoring and management program run by officials in both Russia and North America has been able to prevent this pest from establishing in North American forests. (Image originally published in Mastro et al 2021, Journal of Integrated Pest Management)

So, how did we get to the point where we needed an international, interagency mitigation program for LDA? Well, in the early 1990s, Russia was importing large quantities of grain from North America, primarily out of ports from the Pacific Northwest. It turns out that those ships that originated in Russia were often docked near lights, to which LDA was attracted. Long story short, the moths hitchhiked from Russia to the U.S. via ships. Seems pretty simple and straightforward, and that part is—but what to do next was not so simple. The report in JIPM details how North American and Russian officials were able to work together to install a monitoring program on both sides of the Pacific Ocean—quite a feat considering U.S. and Russian diplomatic relations at the time.

To prevent LDA from hitchhiking to North America, a monitoring program was established at Russian Far East ports and in nearby forests, and the data collected helped predict times of increased risk of hitchhiking (e.g., when adults were flying and egg masses were present). Ship inspection procedures were put in place, and these procedures included education to help on-the-ground personnel recognize and remove LDA life stages. Once a ship was declared LDA free, it received a “certificate of cleanliness” and was allowed into North American ports. This all seems simple in concept, but the reality is dealing with multiple countries most certainly came with many challenges. However, people worked together, the program became very successful, and to this day LDA is not established in North America.

This JIPM paper is filled with details about how this program all came together, as well as how monitoring is conducted in ports and forests. It’s a testament to the forest health and invasive species professionals in all parts of the world in that they can come together to implement programs to benefit countries a world apart. And, since the likelihood of new invasive species never reaching our country again is basically zero, this program provides a great blueprint in how multiple countries can work together to solve a massive problem.

David Coyle, Ph.D., is an assistant professor in the Department of Forestry and Environmental Conservation at Clemson University. Twitter/Instagram/TikTok: @drdavecoyle. Email: dcoyle@clemson.edu.

*On July 7, 2021, the Entomological Society of America announced the removal of the existing common name for Lymantria dispar, “gypsy moth,” from its Common Names of Insects and Related Organisms List, as part of a new ESA program to review and replace insect common names that may be inappropriate or offensive. The Journal of Integrated Pest Management article linked above was accepted prior to this change; articles submitted to ESA journals after July 7 will no longer use the previous common name for L. dispar. Learn more.