Forest tent caterpillar (FTC) is a pest native to the northeast, with outbreaks happening roughly every 10-15 years and generally lasting 2-4 years. FTC is a defoliator that rarely directly causes tree mortality. However, it does place trees under stress, making them more susceptible to other stressors. Using the 100 years of data aggregated in the FEMC Northeastern Forest Health Atlas we extracted records of damage attributed to FTC 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 long-term trends, however the number of years between outbreaks has been decreasing over time.

Highlights

• The most recent outbreak started in 2004 in Vermont, expanding to New Hampshire in 2005 and 2006. In 2007 populations crashed in VT and NH but soared in New York while also appearing in CT and RI. The outbreak continued in New York through 2010. This demonstrates that the extent and location of outbreaks can shift over time.
• Forest tent caterpillar outbreaks typically last 3 years in an area (but may last 2-9) and tend to happen roughly every 10 years. The extensive duration of the most recent outbreak is due to the migration of the pest across the region, with 2-3 year outbreak cycles moving from east to west.¹
• The decrease in total acres damaged and the increase in the percent of damage categorized as mortality indicates that forest tent caterpillar damage is less extensive and more severe, possibly caused by compounding with other stress agents.^{1 2}