Spruce budworm: what the agencies record

This page describes what the named sources say. It is not a diagnosis of any tree and does not say what should be done with one. Each section names its source, all read on October 9, 2026. None of the three publications lists spruce budworm as a regulated or notifiable pest, and none names a report line. The pest has a row in insect pests of trees, and the trees it feeds on are on the balsam fir and red spruce pages and the what attacks spruce register.

Names and hosts

The Maine Forest Service fact sheet (Maine Department of Agriculture, Conservation and Forestry, dated March 13, 2025) gives the scientific name Choristoneura fumiferana and calls the insect native to Maine, always present in the state's forests. It says that in Maine the caterpillars feed mainly on balsam fir and white spruce, readily attack other spruces and larch (tamarack) and eastern hemlock, and occasionally feed on Douglas-fir, white pine and other pines, with no substantial damage on those. The USDA Forest Service Alaska Region leaflet (R10-TP-152, Holsten, revised by Kruse and Lisuzzo, April 2011) says there are at least two budworm species in Alaska that cannot be told apart with certainty without molecular analysis. It names the eastern spruce budworm, C. fumiferana, which feeds mainly on white spruce and is normally found north of the Alaska Range, and the Sitka spruce budworm, C. orae, which feeds on Sitka, Lutz and white spruce and is found mostly south of the Range, though it has populations in the Interior.

Life cycle as the sources state it

Maine says the moths emerge in July, are grayish brown, spotted white and black, with a black bar on both wings, are just over half an inch long with a wingspan of 1 to 1.25 inches, and are often called millers. Large numbers can gather in heavily infested stands and travel great distances on air currents. Alaska gives the adult flight as mid-June to mid-July and says moths can be carried up to ten miles by storm fronts. Maine says that in late July a female lays clutches of about 20 eggs, in pale green masses under the needles, and about 200 eggs in total over the summer; the Alaska leaflet describes a shingled mass of greenish eggs near earlier feeding sites.

The eggs hatch in about ten days. The Alaska leaflet says the newly hatched larvae do not feed at first, and both sources say they spin small silken shelters in cracks and crevices of bark and twigs, where they spend the winter. Maine gives the larva size then as 2 mm. In spring, around mid-May by the Alaska leaflet, they mine into needles and bore into the buds and feed on new growth. Maine says the fifth and sixth instar larvae are the voracious ones, a mature larva being about 1 inch long, dark reddish brown with white spots and a black head. Pupation comes from mid to late June, in loose cocoons or silk webbing among the damaged foliage on twigs, and the adult emerges about 10 to 14 days later by Maine's count, about ten days by Alaska's.

What the damage looks like

Maine says that in late June and July feeding can leave spruce and fir with a reddish-brown upper crown from dead and chewed needles that cling to the branches. In severe outbreaks a whole stand of host trees takes on that colour, which can be seen on the Maine Forest Service aerial surveys, and silken webs between needles may be seen in spring. The Alaska leaflet says feeding is mostly on new growth but older needles can be eaten in heavy infestations, and that consecutive years of heavy feeding can mean complete defoliation and few buds. It lists top-kill, which can leave forked or multiple leaders; a reduction in growth, which it says an outbreak can set back a stand by five to ten years or more; and tree death, which it says rarely occurs in Alaska but is possible in urban settings where trees are stressed by damage or soil compaction. It adds that bark beetles often move into highly stressed trees.

Where the sources place it

Source	Places and activity named
Maine Forest Service (March 13, 2025)	Maine, where the insect is always present and seldom needs control under normal conditions.
USDA Forest Service, Major Forest Insect and Disease Conditions in the United States: 2014 Update (FS-1078, December 2016)	Defoliation continued in the Lake States. None reported in New England in 2014, though adult trap catches in Maine kept rising. Some mortality mapped in Hamilton County, New York. Upper Peninsula of Michigan populations increased; defoliation reported on the Ottawa National Forest over five to six years, with significant spruce and balsam fir mortality. In Minnesota a continuous infestation in the far northeastern counties since 1954, with defoliation acreage nearly doubling in 2014. Damage in northern Wisconsin over five years, most severe in Florence and Marinette counties. None detected in Alaska in 2014.
USDA Forest Service Alaska Region leaflet (April 2011)	Significant damage to white spruce in residential and park areas of Anchorage in 1978; more than 160,000 acres of white spruce defoliated in interior Alaska in 1992; Sitka spruce forests in southeast Alaska also affected.

What the sources say about control

Maine says management is best done by air on a large scale, and that small-scale or single-tree work from the ground is sometimes judged desirable, with any pesticide applied by a licensed applicator. The Alaska leaflet says suppression is not presently necessary on forested land, that damage is minimal when feeding is low to moderate and the spruce are vigorous, and that it lists options for ornamental spruce after two or more years of heavy feeding. This page gives no treatment steps, product names, rates or timings. For who may apply pesticides see pesticide licences.