Douglas-fir Tussock Moth
Early Warning System
Overview
The Early Warning System is a pheromone-based trapping system used to detect outbreaks of Douglas-fir tussock moth (DFTM, Orgyia pseudotsugata) in the western United States. Millions of acres are susceptible to DFTM defoliation, but the Early Warning System focuses attention on the relatively limited areas where outbreaks may be developing. Based on 20+ years of experience in using this system, Daterman et al. (2004, Western Journal of Applied Forestry 19(4): 232-241) published an evaluation and recommendations that are described on this website. A pdf version of the full publication is also available.
Summary: During 20+ years of monitoring, the Early Warning System (EWS) provided warnings of one to three years for 7 of the 9 outbreaks that could be evaluated. No warnings were provided for two of the outbreaks because of inadequate density and distribution of EWS plots in those specific areas. Plots should be evenly distributed over host-type forests at a density of at least one EWS plot per 3000 acres. After potential outbreaks have been identified by the EWS, ground sampling for egg masses and larvae is necessary to characterize local DFTM populations.
EWS data is maintained in an Access2000 database that can be downloaded. This database includes pheromone trap data and plot locations for the years shown in the following table, which was last updated on February 23, 2004. The analyses of Daterman et al. (in press) were based on data from 1979 to 2000.
Number of DFTM Early Warning System Plots
Maintained Annually, by State (1979-2000)
| State | Years covered |
Mean no. plots/yr (all years1) |
Mean no. plots/yr (1991-20001) |
Maximum no. plots |
Minimum no. plots |
| Arizona | 1992-2000 | 9.8 | 9.8 | 15 | 6 |
| California | 1980-2000 | 132.7 | 159.0 | 188 | 74 |
| Colorado | 1986-19992 | 31.3 | 9.0 | 60 | 7 |
| Idaho | 1979-2000 | 129.3 | 187.2 | 208 | 12 |
| Montana | 1979-2000 | 28.9 | 32.9 | 33 | 8 |
| Nevada | 1991-2000 | 6.6 | 6.6 | 10 | 5 |
| Oregon | 1979-2000 | 188.3 | 179.4 | 343 | 48 |
| Utah | 1991-2000 | 6.6 | 6.6 | 7 | 5 |
| Washington | 1980-2000 | 188.2 | 223.7 | 319 | 53 |
| sum of mean plots: | 721.7 | 814.2 | |||
1 Excludes years when no plots were monitored.
2 Plots were not monitored from 1991 through 1994.
Reports summarizing EWS trap catches in Oregon and Washington are available for
2003 (312 KB pdf) and
2002 (1.3 MB pdf).
