ORONO — Over the past few years, browntail moths have been an itchy scourge to Maine’s residents and visitors. New research shows that with climate change, the problem will only worsen.

The browntail moth is an invasive pest that feeds on the foliage of various deciduous tree species and causes acute skin and lung irritation to the people who encounter them. Since it was introduced to Maine in 1904, browntail moth outbreaks have ebbed and flowed, but the recent outbreak of browntail moths that started around 2018 has reached a scale that Maine hasn’t experienced in over 70 years.

A team of researchers from the UMaine School of Biology and Ecology, and the Maine Department of Agriculture, Conservation, and Forestry set out to see whether warming temperatures caused by climate change could have played a role in the severe outbreak. Their study compared predictive statistical models of 23 years of annual browntail moth defoliation estimates for Maine to the climate data from the National Oceanic and Atmospheric Administration (NOAA) throughout that same period.

According to their results, published in the journal Environmental Entomology, climatic factors — particularly rising late summer and early fall temperatures and spring precipitation — are significant predictors of browntail moth population outbreaks. Warmer falls result in more mature populations going into and then coming out of their overwintering shelters in the spring

browntail moth

The Maine Forest Service’s surveys have also shown continued spread of the browntail moth into northern and western areas of Maine over the past two years.

Eleanor Groden, UMaine professor emerita of entomology and principal investigator of the study, says that the researchers explored management strategies targeting caterpillars in their winter webs. Groden’s colleagues — including Angela Mech and Philip Fanning at the School of Biology and Ecology, as well as Barbara Cole in the Department of Chemistry — continue to investigate promising techniques for management of this pest, like using synthetic pheromones to confuse moths during mating season and testing bioinsecticides that specifically target the browntail moth with reduced impacts on other species in the ecosystem.

The browntail moth isn’t the only invasive species in Maine that has benefitted from the warming climate. Some of the browntail moths competitors have also been expanding due to climate change, and the quality of the plants that they feed upon has been waning. Because of this, researchers say that it is difficult to predict what will happen with browntail moths in the future.

“These are important studies, as our current warming climate trends suggest that we will continue to be facing this menace at least in the near future, if not longer,” Groden said.