Killing 200-year-old trees, and only getting worse: Here’s what the spongy moth means to McHenry County

The infestation started last year when Marengo residents Sue and Frank Gualillo noticed the spongy moth caterpillars on their neighbors’ trees. It wasn’t long before they found them on their own property.

Over the course of the summer, it only got worse, as the caterpillars stripped the trees of their leaves. That led to the death and eventual cutting down of several trees – including many that were more than 200 years old. Everywhere you looked, the bugs were covering the foliage, play sets, tire covers and even crossing streets, the Gualillos said.

After they eat and grow, the caterpillars turn into fully formed moths and move on to their next hotspot. But for the Gualillos, a new batch of caterpillars are back this year to continue their raid – and they expect it to be worse this year.

“It’s like living inside a horror movie,” Sue said.

The Gualillos are some of the many homeowners in McHenry County and northern Illinois dealing with the spongy moth, which is threatening trees across much of the north and eastern part of the United States as it migrates west and south.

For Illinois, the moth is most prevalent in the northern part of the state – including McHenry County – where most of the state’s forestry resides, said Scott Schirmer, nursery and northern field office section manager for the Illinois Department of Agriculture.

The infestation in the area is so rampant that the department has become more concerned with preventing the spread of it into the lower part of the state rather than battling it within the northern counties.

“The truth behind it is there just is not an indispensable amount of money to address everything,” Schirmer said. “We’re working in a narrow area beyond the known infested area and trying to slow the advancement of that line.”

The spongy moth – formally known as the gypsy moth before being changed for cultural sensitivity reasons – feeds on the leaves of trees and devoid them of their ability to fight against other diseases, as well as carry out photosynthesis and bring up water and nutrients.

As a result, trees, specifically oak trees, can be killed if left untreated. Typically, a tree can grow back foliage within a few weeks, but if it were to be attacked multiple times in the same season, or over the course of a several years, it can severely weaken its chances of survival.

Jan Vanderspool, a resident in unincorporated Woodstock, said over the past couple years, many of his trees have been defoliated and are showing signs of stress as a result. He worries what another year of an infestation might do.

“It’s frustrating,” Vanderspool said. “I really think the oak trees of the county need help.”

In McHenry County, spongy moths have been a longstanding problem, Schirmer said. While they typically come in cycles – meaning they grow their population over several years – there isn’t much in the way to naturally prevent them from building up.

“It feels like we’ve been thrusted into this battle.”

—  Marengo resident Sue Gualillo on dealing with the spongy moth

Beyond some natural algae that grows, the best way to get rid of them is to spray pesticides, but that can come with risks and be limiting in effect.

On one hand, any effective spray has to come from the air, as working from the ground oftentimes can’t reach the tree’s canopy, Frank Gualillo said.

Meanwhile, spraying can bring risks to other non-invasive moths and caterpillars, said McHenry County Board member Carolyn Campbell, D-Crystal Lake. Campbell also sits on the county’s Planning, Environment and Development Committee and professionally has worked in many conservation roles.

It can also affect the food sources for birds in the area.

“There’s more than just spongy moth’s on those trees,” Campbell said. “I don’t want to give the impression that there’s never a reason to spray, but it’s complicated.”

The county is working with the Department of Agriculture to gather data, which will be submitted at the end of the summer, McHenry County’s Communication and Projects Manager Alicia Schueller said.

Because of the timeline, the degree of the problem this season is not yet known in the county.

However, gathering the data is part of a larger community effort, Schueller said. The data gathered will come from residents reporting what they find on their lands to the Illinois Department of Agriculture. Without that, there’s no way to know how large the problem is.

Going forward, it’s not known if the county or other municipalities will take action themselves to help deal with the situation. Any discussion on that is still in the very early stages, Campbell said.

For the Gualillos, as well as some of their neighbors, they are hoping to see the county get involved. For them and Vanderspool, it can cost thousands to both spray and cut down trees because of an infestation.

“We’re homeowners who mind their own business and do what they’re supposed to,” Sue said. “It feels like we’ve been thrusted into this battle.”