Source: NCDA&CS, 6/11/20

It all started with a few errant caterpillars.

In 1869, French entomologist Étienne Léopold Trouvelot brought the larvae of the Gypsy Moth across the sea intending to breed them with silkworms to create a silk industry in America. Instead, as the story goes, a storm led to several of the larvae being released from his research station near Boston, where they quickly established a presence as an invasive species.

Fast forward to today, and the Gypsy Moth has become such a threat that the North Carolina Department of Agriculture has a program specifically tasked with containing it.

Allison Ballantyne manages the state Gypsy Moth program. She said that the Gypsy Moth’s main threat comes from its appetite.

“It’s an invasive species, and it doesn’t really have enough predators here to keep its population at bay” she said. “So what happens is they reproduce rapidly, and in their larval stage all they do is eat. It’s the only stage of their life cycle in which they actually consume anything.”

When Ballantyne says “all they do is eat,” she means it. A single Gypsy Moth larva can consume a square foot of foliage per day, and when that appetite is multiplied several hundred times the Gypsy Moth becomes a serious destructive force.

The larvae aren’t picky eaters, either. They will eat over 300 different species of hardwood trees – with a particular preference for oaks – which led to Gypsy Moth larvae being responsible for over 75 million acres of defoliation since 1970. The population distribution ranges from North Carolina up the east coast into Canada, and out into the Midwest, Ballantyne said.

Here in North Carolina, the moth is relatively well contained.

“We do see defoliation here in North Carolina, but mostly in our quarantined areas. All of Currituck County is quarantined, and also a portion of Dare County. Higher rates of defoliation can be found in the Northeast and into the Midwest where gypsy moth populations are more dense.”

Defoliation isn’t the only problem that comes with high populations of Gypsy Moths, however. Gypsy Moth larvae are covered in small hairs that they use as a defense mechanism. High concentrations of those larvae can cause problems for people with asthma or other breathing issues, as the hairs will end up floating in the air.

With the Gypsy Moth being such an issue across multiple states, it stands to reason that a joint effort would be necessary to contain it. That’s where the Slow the Spread Foundation comes in. A congressionally-funded, multi-state organization dedicated to containing the Gypsy Moth population, Slow the Spread was originally founded in the late 1990’s before gaining funding from Congress in 2000.

One of the foundation’s major functions is to perform aerial treatments all along the Gypsy Moth’s habitat to slow the species’ growth, including several already beginning here in North Carolina.

“They basically start in North Carolina and go all the way up to Wisconsin to perform these aerial applications as kind of a barrier on the leading edge of the population,” Ballantyne said. “It’s almost the same as if you were treating a forest fire, you treat the leading edge. About seventy percent of the susceptible hardwood forests in the United States have not been infested by gypsy moth, and the goal is to protect them.”

The treatments work by using a synthetic pheromone to disrupt the moth’s breeding patterns, Ballantyne said.

“The female gypsy moth does not fly. She’ll emerge from her pupa and immediately start emitting this pheromone, and the male will use that scent trail to find her in order to mate,” she said. “When we saturate an area with the synthetic pheromone, he’s unable to locate her. He gets confused, they can’t mate, and that’s how we keep their population down.”

A natural side effect of successfully keeping an invasive species at bay is that most people will not be exposed to that species and might not have an appreciation for the havoc they can wreak on an ecosystem. Ballantyne urged people to educate themselves about the impact that the Gypsy Moth and other invasive species like the Spotted Lanternfly can have.

“It’s important for people to understand the work that goes on behind the scenes when managing invasive species. There’s a lot of monitoring, there’s a lot of survey work and it’s a big job,” she said. “We do everything we can to protect the state of North Carolina’s agricultural and natural resources from these pests.”

For more information on some of the invasive species being monitored by NCDA&CS, visit https://www.ncagr.gov/plantindustry/Plant/entomology/index.htm.