Skip to main content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

FVS Models & Event Monitor Files

Gypsy Moth Event Monitor Addfiles

What is it?

The Gypsy Moth Event Monitor is a program that simulates the effects of gypsy moth within the confines of the Forest Vegetation Simulator (FVS). Individual stands are evaluated with a susceptibility index system to determine the vulnerability of the stand to the effects of gypsy moth. A gypsy moth outbreak is scheduled in the FVS multi-year cycle if a drawn random number is less than or equal to the estimated probability of outbreak in that multi-year cycle. If an outbreak is scheduled, gypsy moth mortality is leveled against species deemed susceptible and resistant; basal area growth is increasingly reduced in susceptible species during light, medium and heavy outbreaks, whereas during a heavy outbreak, basal area growth is somewhat reduced in resistant species.

This is a strategic model that demonstrates the potential loss of timber and habitat due to gypsy moth. The user can proactively reduce the stand’s susceptibility to gypsy moth and the probability of a gypsy moth event by scheduling appropriate management actions within FVS (see Gottschalk 1993). Due to the limitations in FVS’s growth and mortality equations, the variability normally seen in response to gypsy moth defoliation cannot be adequately modeled. As such, the user is cautioned that the best use of this Event Monitor is to show relative differences in responses of stand to gypsy moth rather than predicting absolute responses in individual stands. The Gypsy Moth Event Monitor can be used to prioritize stands for treatment or to estimate the overall impacts to a forested landscape.

Who should use it?

The Gypsy Moth Event Monitor is intended for use by those familiar with the proper use and execution of the Forest Vegetation Simulator. It is recommended that the user be well versed in interpretation of standard FVS output. Specific Event Monitor variables can be exported to spread sheet programs for further user analysis.

How do I use it?

The Gypsy Moth Event Monitor is an FVS Addfile, which typically have a "*.kcp" file extension. The geographically appropriate Event Monitor must be added to the simulation, after one or more stands have been selected for use within FVS. The Gypsy Moth Event Monitor Users Guide included with the event monitor files describes how to use the addfile, evaluate its results, and who to contact with questions.

Which Gypsy Moth Event Monitor Files do I use?

There are eight types of gypsy moth keyword component (.kcp) addfiles appropriate for use with FVS, two for each of the four supported variants: Northeast (NE), Central States (CS), Lake States (LS), and Southern (SN). Users who wish to simulate the effects of Gypsy Moth should use GM_NE_1985.kcp, GM_CS_1985.kcp, GM_LS_1985.kcp or GM_SN_1985.kcp dependent upon stand location and their preferred FVS variant. Users who wish to only track the susceptibility of stands to gypsy moth should use GM_NE_SUSC.kcp, GM_CS_ SUSC.kcp, GM_LS_ SUSC.kcp or GM_SN_ SUSC.kcp, dependent upon the preferred variant.

FHAAST will create additional gypsy moth event monitor files for other variants upon request.

The user is strongly urged to apply the correct Event Monitor File to the appropriate stands. This is best achieved by creating geographically homogenous FVS simulations or through creative use of FVS grouping codes.


Gypsy Moth Event Monitor (GMem.exe, 132 KB, updated 07-18-2005)

gypsy moth

Head shot of late instar gypsy moth feeding on white oak. Photo by John Ghent.