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What attacks fir and Douglas-fir: pests the sources name

A register of the woolly adelgid, the spruce budworm, the spruce gall adelgid and the armored scale that Natural Resources Canada, the Maine Forest Service, Utah State University Extension, Penn State Extension and NC State Extension tie to true firs and to Douglas-fir: which tree each row names, where it is recorded, and where the full profile is.

Checked against the sources at the bottom of this page on October 9, 2026. Rules, fees and pay change: the source has the last word.

This page reports what the named sources say. It is not a diagnosis of any tree and does not say what should be done with one. Each row names its source, all read on October 9, 2026. Where this site has a full profile, the row links it. The register is short because the sources read give separate facts for four agents. Utah State University Extension points out that Douglas-fir is not a true fir, and the two groups differ in which rows apply. The trees themselves are on the balsam fir, subalpine fir, white fir and Douglas-fir pages.

The register

AgentWhat the sources record
Balsam woolly adelgid, Adelges piceae. Full profileKind: Sap-feeding insect
Hosts: True firs only. Natural Resources Canada says balsam fir in eastern Canada and subalpine fir in western Canada are most vulnerable, with amabilis fir and grand fir less so. Natural Resources Canada links it to the decline of Fraser fir and balsam fir in the eastern United States. Utah State University Extension says Douglas-fir is not affected.
Where: Eastern North America from Newfoundland south through the Appalachians to Tennessee, and the Pacific Northwest, California and parts of British Columbia in the West.
Symptoms as listed: Swollen twig nodes called gouting, red needles, dieback from the top of the crown and white woolly wax on bark.
Spruce budworm, Choristoneura fumiferana. Full profileKind: Native moth whose caterpillars eat buds and needles
Hosts: The Maine Forest Service says balsam fir and white spruce are the main hosts in Maine, and that Douglas-fir is occasionally fed on with no substantial damage.
Where: Maine, where the insect is always present; the USDA Forest Service 2014 report says spruce and balsam fir mortality had become significant on the Ottawa National Forest in the Michigan Upper Peninsula.
Symptoms as listed: A reddish-brown upper crown from dead and chewed needles that cling to the branches, and silken webs between needles in spring.
Cooley spruce gall adelgid, Adelges cooleyi. Gall profileKind: Gall-forming adelgid that alternates between two hosts
Hosts: Natural Resources Canada names Douglas-fir as the secondary host, with western spruces such as Sitka, Engelmann, white and Colorado blue spruce as primary hosts. On Douglas-fir it describes white woolly wax at the feeding site and discoloured, distorted needles.
Where: Native to western North America, introduced to eastern North America, the United Kingdom and northern Europe, in places where host trees from North America were planted.
Weight given: The factsheet says it is not considered a major pest in forest settings.
Elongate hemlock scale, Fiorinia externa. Full profileKind: Armored scale insect
Hosts: Penn State Extension lists fir and spruce among the principal hosts, and Douglas-fir as a host that is not preferred, usually infested when growing next to infested hemlocks. NC State Extension names hemlocks and true firs, Fraser fir among them, as the most common hosts in western North Carolina.
Where: NC State Extension says more than 14 states in the eastern United States.

How the sources describe the effects

Natural Resources Canada says balsam woolly adelgid infests all age classes of true fir and can kill a tree in as little as two to three years, and that it caused significant mortality of balsam fir in Atlantic Canada after the 1940s. Utah State University Extension says that in some areas of North America it has completely removed true firs from forest stands. For the spruce gall adelgid the effect on Douglas-fir is discoloured needles, and the galls themselves form on the spruce host. NC State Extension says an elongate hemlock scale infestation that does not reduce growth can make a Christmas tree unsaleable.

Who the sources say to report to

None of the pages read for these agents names a report line. The offices for each country are on the report a pest in Canada and report a pest in the United States pages.

Sources