Lymantria Dispar / Spongy Moth (Historically Gypsy Moth)

Lymantria dispar Open Houses Spring 2023
DATE	TIME	LOCATION	ADDRESS	PHONE	SPRAY AREA

Lymantria dispar:

Lymantria dispar caterpillars consume as much leaf tissue as they can, as quickly as they can, to obtain nourishment to become reproducing adults. Since the caterpillars' feeding period lasts seven to ten weeks through spring and summer, they can do a lot of damage to young tree leaves. If a tree loses more than 50% of its leaves for more than two years in a row, it will certainly be weakened and may not survive. A single Lymantria dispar caterpillar can consume 11 square feet of vegetation during its lifetime so the presence of millions of caterpillars can severely affect trees and forests.

During large outbreaks, trees are virtually stripped of their leaves by hungry caterpillars within a few days. Although most trees will re-grow new leaves before summer's end, the process stresses the tree and drains its reserves. Weakened trees and shrubs, especially those in urban settings, are more susceptible to attack by opportunistic diseases and organisms. In addition, the tree's growth rate is impaired, which affects its chances for survival during the following years.

What is Illinois doing to control Lymantria dispar?

The Illinois Department of Agriculture and USDA APHIS, along with the STS Foundation, place over 10,000 traps to monitor populations each year. Each year, the monitoring is tabulated, and eradication treatments, usually aerial applications, of Btk (Bacillus thuringiensis kurstaki) or mating disruption are decided for the following year.

The Lymantria dispar is migrating west, and it has established itself in Illinois. Lake County, Illinois was quarantined in 2000. The counties of McHenry, Cook and Du Page were added in 2007, Kane, Kendall, Will & Lasalle were then added in 2017. In 2022, 2 more counties, Winnebago and Boone were added. A quarantine requires all nursery stock and firewood being shipped out of the affected counties to be inspected and certified. All nurseries and nursery dealers are also required to treat their property and/or stock, and persons leaving quarantined counties must have all outdoor equipment inspected.

For more information on this invasive insect and The Slow the Spread program click the story map below:

National Slow the Spread Program

Read the history and overview of the Slow the Spread Program. This story includes information on:
Introduction & Spread,
Biology & Ecology,
Management History,
Shared Stewardship,
and the STS Program.