Researchers didn’t see Emerald ash borer (EAB) coming, and the spread has been devastating -- killing tens of millions of trees. The troublesome beetle most likely entered the U.S. through wood crating or pallets used for shipping cargo from Asia and led to a full-blown plant health emergency. 

Deborah McCullough, MSU forest entomology professor, has worked with other researchers, technicians and her students on EAB population dynamics, spread, impacts and control. 

“We collected tree rings across a 5,800 square mile area in southeast Michigan and found that emerald ash borer had arrived in the Detroit metro area near Westland and Garden City by at least the early 1990s, but it wasn’t discovered until 2002,” she said. “EAB is now in 35 states, five Canadian provinces and is considered the most destructive and costly forest insect to ever invade North America.”

McCullough, who has a research, teaching and MSU Extension appointment, collaborates with the Michigan Department of Natural Resources (DNR), Michigan Department of Agriculture and Rural Development (MDARD), the U.S. Forest Service and United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS). Her role is to provide research and options for the operational people who must manage these pest issues. 

“In the case of EAB, there was very little research when it was discovered and in many ways, we started from scratch. We needed to learn the life cycle of the insect and develop methods to survey for it, control it, and to tell people confidently what they could expect about impacts.”

EAB wasn’t the first plant health emergency, and it won’t be the last. Right now, McCullough and her team are working on hemlock woolly adelgid (HWA), a tiny, sap-feeding insect native to Japan. Populations of HWA are in five counties in the state, mostly along the Lake Michigan shoreline. 

“This insect has killed thousands of hemlock trees in the eastern US since the 1950s,” she said. “In New England and on the East Coast, we know that when the hemlock trees die, everything changes. It affects important wildlife habitat along with soil chemistry, other vegetation and streams and rivers. Eastern hemlock trees are very abundant in northern Michigan and are really vulnerable to HWA. Nobody wants to see this invader spread, so many of us are collaborating on surveys and control tactics to help contain it.”  

With HWA, McCullough and her team have a foundation of research to build upon. 

“In the east, people have been dealing with this for decades, so we look at what they’ve done and what can we apply here in Michigan. We analyze where we need additional research because things like climate and forests are not exactly the same in Michigan. Part of our work includes adapting what has been successful in other areas and making sure that we have solid and practical tools here.”

Over 10 years, McCullough worked with a team of people from across the country: ecologists, forest entomologists and economists, and identified over 450 invasive forest insect species and the ones causing the most damage, from both ecological and economic perspectives. 

“At the time, we found 454 established non-native forest insects in the U.S.,” she said. “Fortunately, only 62 are considered to be damaging,” she said. 

“When you look at forest pathogens, there were only 16 species, but all of them cause damage. I think that it partly tells you that people give a lot of attention to insects. You can see and catch insects. People like moths, butterflies and beetles. But pathogens, unless that pathogen is causing problems, causing trees to decline or die, nobody can know what might be floating around out there until someone notices a problem.”