Summary of DFTM Outbreaks in the Western US (1979-2001)
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| Acres Defoliated | No. of nearby plots3 | Plot density (ac/plot) | ||||||||
| Out- break no. |
Outbreak name | State | Starting year1 | Ending year2 | Initially defoliated area |
Maximum area defoliated |
Initially defoliated area |
Maximum area defoliated |
Initially defoliated area |
Maximum area defoliated |
| 1 | Owyhees | ID | 1981 | 1983 | 160 | 14,200 | 1 | 2.5 | 160 | 5,680 |
| 2 | NE Washington | WA | 1982 | 1983 | 3,030 | 20,300 | 1.5 | 3.5 | 2,020 | 5,800 |
| 3 | Northern Idaho -1 | ID | 1986 | 1986 | 3,390 | 3,390 | 3.7 | 3.7 | 916 | 916 |
| 4 | Plumas/Lassen | CA | 1987 | 1989 | 7,500 | 105,000 | none | 3.0 | n/a | 35,000 |
| 5 | Southern Idaho | ID | 1990 | 1992 | 50,800 | 418,000 | 3.0 | 10.0 | 16,933 | 41,800 |
| 6 | NE Oregon-Pine RD | OR | 1990 | 1992 | w/ wsb4 | w/ wsb4 | n/a | n/a | n/a | n/a |
| 7 | Wasatch-Cache5 | UT | 1990 | 1992 | 2,900 | 4,900+ | none | none | n/a | n/a |
| 8 | NE Oregon-Malheur NF | OR | 1992 | 1995 | 6,630 | 62,400 | 2.0 | 2.0 | 3,315 | 12,480 |
| 9 | Keller's Ferry5 | WA | 1993 | 1993 | 278 | 278 | none | none | n/a | n/a |
| 10 | Pike NF5 | CO | 1993 | 1995 | 250 | 6,100+ | none | none | n/a | n/a |
| 11 | Giant Sequoia NM | CA | 1997 | 1999 | 3,500 | 5,800 | none | none | n/a | n/a |
| 12 | Modoc | CA | 1999 | 1999 | 2,200 | 2,200 | 3.0 | 3.0 | 733 | 733 |
| 13 | Blue Mountains | OR,WA | 1999 | 2001 | 21,000 | 220,000 | 8.0 | 10.7 | 2,625 | 20,561 |
| 14 | Northern Idaho-2 | ID | 2000 | ?6 | 54,700 | n/a6 | 31.0 | n/a6 | 1,765 | n/a6 |
1 First year that defoliation was detected by aerial surveys. Sources: annual Forest Service insect and disease conditions reports and digital files; on file at Forest Health Protection, Natural Resources, Pacific Northwest Region, USDA Forest Service, P.O. Box 3623, Portland, OR 97208.
2 Last year that defoliation was detected by aerial surveys.
3 Mean number of plots within 1 mile of the initially defoliated area for the 3 years prior to the starting year (exceptions: for outbreaks 1 and 2, the mean for 2 years prior to the first year of the outbreak is listed).
4 Defoliation by both tussock moth and western spruce budworm occurred in the same stands; aerial surveyors generally could not determine which insect was responsible for the observed defoliation.
5 Early Warning System not monitored within 10 miles of the defoliated area prior to these outbreaks.
6 Outbreak was ongoing at the time this manuscript was written.
