Lymantria dispar (formerly known as gypsy moth) is a non-native pest originally introduced to North America in the 1860s and established in the northeast since the early 1900s. Using the 100 years of data aggregated in the FEMC Northeastern Forest Health Atlas we extracted records of damage attributed toL. dispar across the region and assessed outbreak events using annual forest health reports.

Analysis

• Frequency
• Extent
• Severity
• Location

Disturbance Trend Summary

There are too few outbreak events in the historical record to analyze the trend in outbreaks, however, the number of years between outbreaks has increased over time indicating that outbreaks may be happening less often.

The overall trend in the total acres damaged by L. dispar and the percent of all damage that is categorized as mortality are increasing significantly.

Highlights

• The 1981 outbreak is the worst in the history of L. dispar in North America damaging more than 6 million acres across the region.
• In 1989 a fungus - Entomophaga maimaiga - that is a native biological control to L. dispar in Japan was first found established in the region and impacting L. dispar populations in North America. It significantly contributed to the decline of the 1980s outbreak and to L. dispar population management since. In 2015 and 2016 conditions in the northeast were too try for E. maimaiga resulting in a dramatic increase in L. dispar populations. ^{1 2}