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How to identify it
- The adult is a small weevil, about 0.1 inch long, grayish black with white markings and sometimes pinkish or orange spots, and it is wingless. UC Cooperative Extension describes the body as bronze, sometimes with white spots, with a long beak.[1][2][3]
- Infested twigs and small branches turn reddish brown and die back. On seedlings, light larval feeding shows as scattered patches of reddish-brown bark against green healthy tissue, and heavily infested stems look swollen around the larval wounds with dieback above them.[1][4]
- The surest check is to split a dead twig or stem: finding the larvae, or their L-shaped pupation chambers in the wood, separates twig weevil damage from frost injury and other kinds of dieback, which it can closely resemble.[4]
- Adults chew small feeding holes in the needles, but this damage is mild compared with the larval mining.[3]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Douglas-fir pole beetle and Douglas-fir engraver (bark beetles) | Both can also flag branches or kill the top of a Douglas-fir, but their effects are usually more widespread in the tree, and they make galleries with many larval chambers on the main stem and large branches. Twig weevil larvae bore individually into twigs and small branches.[3] |
| Frost damage | Dieback from larval feeding on seedlings is easily mistaken for frost damage. Splitting the dead stem to look for larvae or their L-shaped pupation chambers is the reliable way to tell them apart.[4] |
| Other Cylindrocopturus twig weevils | Several related weevil species attack pine and true fir in the Pacific Northwest.[1] |
Where it lives
A western weevil that breeds in young stem tissue of Douglas-fir on the west side of the Cascade Range. It has long been an occasional problem for Christmas tree growers in the Pacific Northwest, and in 1976 it turned up in newly planted Douglas-fir plantations in Oregon's Willamette Valley, where it caused serious dieback and killed some seedlings. In California it is reported on Douglas-fir and occasionally true firs.[4][3]
Biology and life cycle
The weevil overwinters as a larva or an adult. Adults emerge from June through early August and lay their eggs in twigs during the summer.[1]
Larvae feed by mining just beneath the bark and pupate at the ends of their galleries the following spring. There is one complete generation a year plus a partial second. UC Cooperative Extension notes that larvae are present all year but bore most actively from January into May, and that adults can be found year round, most obviously in summer.[1][3]
The host was long thought to be Douglas-fir only, but in recent years the weevil has been found on true firs as well, including Nordmann, noble and Turkish firs. In the Oregon plantation outbreak the weevils bred only in living Douglas-fir, and populations probably built up in trees bordering clearcuts before moving onto the new seedlings.[2][4]
Like other boring insects, the weevil may carry fungal spores into the tree and add to its pathogen load.[3]
Damage and signs
- Larvae mine under the bark of twigs and small stems, killing small terminal and lateral branches. On seedlings this often leaves a forked top and an odd branch structure.[1][3]
- Small, stressed trees and trees in Christmas tree plantations are the most susceptible, particularly in dry years. The weevil can kill small branches and sometimes small trees.[1][2]
- In the 1977 Oregon survey of five new plantations, 90 percent of the damage was on the main stem of planted seedlings. On average 16 percent of the larger planted seedlings had serious damage, dieback or death, and 24 percent in the worst plantation, though most seedlings with dieback were expected to recover. Smaller seedling types were barely touched. Weevil numbers rise and fall quickly: on untreated trees, infestation dropped from 38 percent in 1976 to 12 percent in 1977.[4]
Health risk
A conifer twig borer; none of these sources describes any risk to people.[1][3]
Control
Prevention
Keep trees healthy with good cultural practices; vigorous trees withstand the weevils better. Avoid planting Douglas-fir on drought-prone or wet sites. The Pacific Northwest handbook notes that cultural control is frequently the only practical option.[1][2][3]
Traps and physical control
Watch for wilting or reddish-brown twigs and branch tips. Pick off adults when you see them, and remove and burn infested twigs, branches or whole trees before the new adults emerge in June.[1][3]
Biological control
No biological control is indicated for this weevil.[1]
Pesticides
For Christmas tree plantations the Pacific Northwest handbook lists bifenthrin and esfenvalerate, both restricted-use pesticides, and notes that some are not registered in Washington. Landscape treatments are referred to the handbook's landscape pest table.[2][1]
Common questions
- Why are the branch tips on my young Douglas-fir turning red?
- Reddish-brown, dying twigs and branch tips on a small or stressed Douglas-fir, especially in a dry year, fit the Douglas-fir twig weevil, whose larvae mine just under the bark. Split a dead twig: larvae or L-shaped pupation chambers in the wood confirm it, and separate it from frost damage.[1][4]
- Will the weevil kill the tree?
- It usually kills only small branches, but it can kill small trees, and in new plantings it has killed seedlings and caused forked tops. Most seedlings with dieback recover.[2][3][4]
- When should I prune out infested twigs?
- Before the adults emerge. Adults come out from June through early August, so cut and burn infested twigs before June.[1][3]
Sources
- Pacific Northwest Pest Management Handbooks (Oregon State University, Washington State University, University of Idaho), “Douglas-fir (Pseudotsuga)-Douglas-fir twig weevil (Pacific Northwest Insect Management Handbook, landscape pests).” pnwhandbooks.org/insect/hort/landscape/hosts-pests-landscape-plants/douglas-fir-pseudotsuga-douglas-fir-twig-weevil (accessed 2026-11-10)
- Pacific Northwest Pest Management Handbooks (Oregon State University, Washington State University, University of Idaho), “Christmas tree-Twig weevil (Pacific Northwest Insect Management Handbook, Christmas tree plantation pests).” pnwhandbooks.org/insect/hort/christmas-tree/christmas-tree-twig-weevil (accessed 2026-11-10)
- University of California Cooperative Extension, Humboldt and Del Norte Counties, “Douglas-fir Twig Weevil (Cylindrocopturus furnissi), Forest pests and pathogens.” ucanr.edu/node/130411 (accessed 2026-11-10)
- USDA Forest Service (Tree Planters' Notes, Reforestation, Nurseries and Genetics Resources archive), “Overhulser, Walstad and Bowers. Twig weevil damage to Douglas-fir seedlings and a field test of Dursban for control. Tree Planters' Notes 31(2): 17-20 (1980).” npn.rngr.net/publications/tpn/31-2/31_2_17_20.pdf/at_download/file (accessed 2026-11-10)
- iNaturalist, “Cylindrocopturus furnissi taxon page (order and family).” www.inaturalist.org/taxa/48906 (accessed 2026-11-10)