Angela Mech, assistant professor of Entomology at University of Maine, has been leading the research for the i-Tree pest predictor. Mech specializes in invasive forest insects. University of Maine photo

MAINE — As nonnative insects continue to surge in numbers, i-Tree pest predictor could predict the next species to become a pest before it arrives in Maine.

University of Maine’s Angela Mech is an expert on invasive forest insects. As a researcher, Mech has led the effort to create the tool. Eighteen other experts have contributed to the databases that inform i-Tree’s predictions.

“When talking about nonnative insects that invade North America, the first time something is detected, those of us who work in the field hold our breath, because we have no idea if it’s going to be the next emerald ash borer, the next browntail moth, the next really bad thing,” Mech said.

Maine’s forests are vulnerable to nonnative insects in particular because of the state’s proximity to global trade ports.

“The northeast of the United States is one of the most invaded regions in the country when it comes to forest pests,” Nathan Havill, a researcher with United States Department of Agriculture National Forest Service’s Northern Station, said. “We see a steady increase in the number of nonnative insects that keep getting introduced. There are enormous numbers of goods coming into the country from other places. They can’t all be inspected for pests before they come in.”

Many insect species make their way through different goods and ports, but fail to establish a presence in the new environment.

“We were interested in trying to figure out what makes some invasive species be very, very harmful and others completely harmless,” Mech said. “In fact, over 90% (of nonnative insects) are harmless.”

The few that thrive in the new environment can threaten entire species of trees, and in rare cases, human health.

“In Maine, we do have invasive species that are attacking our trees that are very concerning: emerald ash borer that many folks might have heard about; the spongy moth, which was formerly known as gypsy moth, and the browntail moth. So, these are all the ones that we know about in that 5-10 percent (of harmful nonnative), the really damaging ones that affect our ecosystems,” Mech said.

Mech said she believes changes in the climate might be pushing pests farther north. “They’re able to survive better when we have warmer winters,” Mech said. “(Cold winters) used to be one of the factors that kept bugs’ survival rates down here (in Maine.)”

“For example, hemlock woolly adelgid is predicted to be able to spread north farther with climate change and become a pest,” Havill said. “But whether there’s a correlation with climate change and more insects coming in, I don’t think that’s been shown necessarily.”

Portland’s city arborist, Jeff Tarling, points out damage Tuesday from emerald ash borers on a now-dead ash tree near the Portland-Westbrook line. Brianna Soukup/Staff Photographer

The i-Tree uses a combined database of tree and insect traits to predict the chances a newly arriving insect will become an invader. The database includes over 50 conifer species and 360 hardwood species native to North America, many of which can be seen across Maine’s forests.

“We looked at the over 400 invasive species that have already invaded North America,” Mech said. “We tried to see whether or not we could draw conclusions about their traits or the trees. We came up with all these hypotheses and then merged them into this really crazy statistical model, but now that is a tool that we made available for everybody to use.”

Mech said 99% of nonnative insects do not impact human health.

“When we have an entire tree species get attacked, like all of the ash trees by emerald ash borer, that can impact birds that are dependent upon ash trees for nesting or other insects that feed on ash trees, and then the critters that feed on those insects and so on,” Mech.

In very rare cases, nonnative insects can hurt humans too.

“The one exception in Maine is the browntail moth,” Mech said. “It’s damaging to the trees and the forest, but it does have toxic hairs that cause a poison ivy-like rash on humans too.”

Havill said pests could have an indirect impact on human health through heat islands.

“Having trees, especially urban trees, is important for human health. For example, emerald ash borers kill ash trees, a major urban tree,” Havill said. “When that happens, we get large (urban) areas with no trees, leading to heat islands.” In the absence of tree shade or trunks, heat islands are areas that trap and hold onto the heat, especially in cities.

Angela Mech, assistant professor of Entomology at University of Maine, has been leading the research for the i-Tree pest predictor. Mech specializes in invasive forest insects. University of Maine

“If we have a new species from somewhere else that invades North America, this predictor will determine whether or not any of our North American trees have a high risk of getting damaged by that insect,” Havill said. “If something was just detected at a port of entry, and folks want to know whether or not any of our trees would be at risk, they could plug in the information about that insect and then the tool would produce a list of North American trees and the risk of that particular insect being damaging to those trees.”

Once a threat has been identified, measures can be taken to avoid or reduce damage.

“The tool wouldn’t really be beneficial for nonnative insects that are already here,” Havill said. “It’s really good for state or federal agencies if they detect some new insect. They can determine what trees might be most at risk and then focus their attention and resources on those trees.”

Havill also encouraged folks who work with trees to use the tool if they encounter insects they cannot identify.

The i-Tree pest predictor is available at pestpredictor.itreetools.org/predictions.