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How to identify it
- Fine, reddish sawdust-like frass in the lower bark furrows of European linden, especially in May and June, is the sign to look for. Underneath, the inner bark is honeycombed by larval tunnels, and in some reports the outer bark is so damaged it crumbles by hand.[1]
- Full-grown larvae are whitish with light brown heads and only about 6 mm long, living inside the bark.[2][1]
- The adults are small, brightly colored day-flying moths; in Canada clouds of hundreds or thousands have been seen flying around infested trees.[1]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Linden looper | A bright yellow, black-lined inchworm that eats the foliage of basswood and many other hardwoods; the linden bark borer never touches the leaves and works unseen inside the bark.[2][1] |
Where it lives
Introduced from Europe. First reported in 1928 near New York City, then in surrounding parts of New York and New Jersey and near Boston; UMass adds Connecticut, Vermont and parts of Canada. The Forest Service's 1972 manual said its full distribution was not known, and UMass says further study is still needed to confirm its pest status in Massachusetts.[2][1]
Biology and life cycle
Adults fly from late May to mid-June according to the Forest Service, or about May to August according to the reports UMass cites, with a flight of 7 to 10 days in early June in Massachusetts. They are thought to lay their eggs on the branches of the host.[2][1]
The larvae bore into and tunnel through the bark, pushing out rusty colored frass, and spend the winter in the bark as larvae. Pupation occurs in early spring in cells formed in the galleries close to the bark surface, once the larvae reach about 6 mm.[2][1]
A single generation a year is reported, but little about the biology of this species is known.[1]
Damage and signs
Health risk
Neither source mentions any effect on people; the insect lives in linden bark.[1][2]
Control
Prevention
Check European lindens for reddish, fine frass in the lower bark furrows in May and June; this is the only monitoring method UMass gives. Information on cultural management and natural enemies is currently unavailable.[1]
Pesticides
UMass lists abamectin, acephate, azadirachtin, chlorantraniliprole, cyantraniliprole, imidacloprid, neem oil, permethrin and spinosad as active ingredients whose Massachusetts labels cover lepidopterous larvae or borers in general; none is labeled for this species by name. Apply after bloom to protect pollinators.[1]
Common questions
- What is the rusty sawdust in the bark furrows of my linden?
- Frass pushed out by linden bark borer larvae tunneling in the bark; it is most visible in the lower furrows of European linden in May and June.[1]
- Will the linden bark borer kill my tree?
- Nobody knows for sure. Heavy infestations honeycomb the inner bark from the ground into the crown, but UMass says the short- and long-term impacts on the host still need study.[1]
- Where did this moth come from?
- It is native to Europe and was first found in North America on lindens near New York City in 1928.[2][1]
Sources
- UMass Extension Landscape, Nursery and Urban Forestry Program, University of Massachusetts Amherst, “Chrysoclista linneella (formerly Glyphipterix linneella), Linden Bark Borer Moth, Insect & Mite Guide (Professional Guide for IPM in Trees and Shrubs).” www.umass.edu/agriculture-food-environment/landscape/publications-resources/insect-mite-guide/chrysoclista-linneella-formerly-glyphipterix-linneella (accessed 2026-11-10)
- USDA Forest Service, “Eastern Forest Insects, Miscellaneous Publication 1175 (W. L. Baker, 1972; scanned copy).” archive.org/details/easternforestins1175bake (accessed 2026-11-10)
- iNaturalist, “Chrysoclista linneella taxon page (order and family).” www.inaturalist.org/taxa/364095 (accessed 2026-11-10)