Say hello to a male spongy moth, aka Lymantria dispar, with its remarkable bat-like antennae. – Getty Images
As a caterpillar, the invasive spongy moth consumes as much leaf tissue as it can, as fast as it can, threatening the lives of whole forests across the upper Midwest.
But Illinois continues to stand on the front lines when it comes to slowing the westward spread of this insect with a voracious appetite.
To protect our trees and contain the insect’s migration, county forest preserve districts are working with the Illinois Department of Agriculture to treat various natural areas in the greater Chicago region, including in Aurora, Lemont and Naperville.
Historically known as the “gypsy moth,” spongy moth caterpillars have a feeding period that lasts seven to 10 weeks through the spring and summer. A single spongy moth caterpillar can eat 11 square feet of vegetation during its lifetime, and its host plants include more than 300 tree and shrub species.
With the ability to completely strip trees bare year after year, spongy moths have the potential to severely affect trees and forests. But since an Illinois county was quarantined first — Lake County in 2000 — two types of prevention treatments have proved successful at holding the line, or least slowing it down.
The yearly treatments involve low-flying helicopters or yellow agricultural planes that release either a pesticide or a mating disruption agent.
Spraying of the insecticide, known as BTK or Bacillus thuringiensis kurstaki, took place last month in areas in Aurora, Galena, Lemont and West Chicago. BTK solely affects caterpillars and is not toxic to people, animals or other insects. The insecticide has been used in the greater Chicago area since 1980.
While that means BTK kills all caterpillars and not just spongy moths, studies show the agent does not have long-lasting effects on native species, said Scott Schirmer, a plant regulatory official with the Illinois Department of Agriculture.
“We’re basically dumping a bucket of water on the spongy moth campfire. That area is going to be eliminated of spongy moths, but there’s going to be all the natives in the surrounding area that can basically backfill into that hole relatively quickly,” Shirmer said. “Studies show that the natives will repopulate or recolonize an area that’s been treated with BTK in a matter of a couple of years.”
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