Language selection

Government of Canada / Gouvernement du Canada

Search

Beech leaf-mining weevil

Written by J.D. Sweeney Revision 2025

General information and importance

Beech leaf-mining weevil is a common defoliator of European beech (Fagus sylvatica) in Europe. In its native range, occasional outbreaks by the weevil reduce tree growth rates and beech nut production but do not cause tree mortality. The weevil was first recorded in 2012 in Halifax, Nova Scotia. Since then, it has spread throughout the province and into neighboring New Brunswick and Prince Edward Island, likely aided by inadvertent human-assisted movement. Contrary to the relatively minor impacts on European beech, more than 90% mortality of mature American beech (F. grandifolia) has been recorded in Nova Scotia after 5 to 7 consecutive years of defoliation by beech leaf-mining weevil. As the invasive beech leaf-mining weevil spreads in North America, it threatens the health of American beech, an ecologically important species already experiencing significant damage from other invasive pests, such as beech bark disease and beech leaf disease.

Distribution and hosts

Beech leaf-mining weevil is distributed throughout the range of European beech in Europe. In North America, it was already well established within a 30-kilometre radius of Halifax as well as in parts of Cape Breton in 2012. Annual surveys conducted in Nova Scotia, New Brunswick, Prince Edward Island, Quebec, and Newfoundland and Labrador from 2012 to 2017 by the Canadian Food Inspection Agency detected the weevil in four additional counties in Nova Scotia but not outside of the province. In 2021, the weevil was detected in Prince Edward Island and New Brunswick. It is difficult to know the extent of the current distribution of beech leaf-mining weevil in North America because there have been no formal annual detection surveys conducted since 2017. However, the potential for the weevil to eventually spread throughout the range of American beech in North America is considerable.

The main hosts of beech leaf-mining weevil are European beech and American beech (Fagaceae). In Europe, adults of beech leaf-mining weevil have been observed feeding on the foliage of as many as 14 plant species in early spring prior to beech budburst, including common hawthorn (Crataegus monogyna) and red raspberry (Rubus idaeus). During outbreaks of the weevil in Germany, adult feeding has damaged fruits of apricot and cherry (both species of Prunus), and apple (Malus) trees growing near beech. However, in no-choice feeding bioassays conducted with beech leaf-mining weevil adults from populations established in Nova Scotia, little to no feeding on any species other than American beech was observed. Except for a rare report of adult emergence from foliage of willow oak (Quercus phellos) and Hungarian oak (Q. frainetto) in a British Arboretum, successful development of beech leaf-mining weevil from egg to adult is known only to occur on European and American beech.

Tree parts affected

Foliage. Occasional reports of damage to tree fruits in Europe growing in close proximity to infested European beech in Europe.

Symptoms and signs

Feeding by adults on the young developing leaves creates typical shot holes as the leaves expand. Larval mines begin at the mid-rib and expand in width as they move towards the leaf margin. Larvae are white with a black head and about 5 millimetres long when mature. Pupation occurs within the leaf in a blotch mine. In heavy infestations, leaves will be stunted with necrotic tips, making the foliage appear scorched and the crown thin and sparse. Adult weevils are small, 2.2 to 2.8 millimetres long, black with golden pubescence, and well-developed hind legs that allow them to jump several centimetres. They are easily observed by beating (with either a beat sheet or blanket underneath to capture the dislodged insects) beech branches after budburst in spring.

Life cycle

Beech leaf-mining weevil has one generation per year. Adults are present most of the year and overwinter primarily on the trunks of trees (especially beech cankered by beech bark disease, but they can also be found on maple and spruce trees) in crevices and under bark scales or moss. They may also be found in leaf litter and on the foliage of spruce trees. Adults emerge from reproductive diapause in spring and may be found feeding and mating on young developing beech leaves at the time of budburst. Females lay 40 to 50 eggs (0.6‒0.7 millimetres long) singly along the mid-rib on the underside of developing leaves. Larvae mine the leaves from the mid-rib towards the leaf margin and go through three instars before pupating within a white cocoon inside the leaf mine. The new generation of adults may or may not feed on foliage before seeking overwintering sites. The time from egg to adult is 30 to 35 days.

Damage

The weevil has caused severe defoliation, crown dieback, and mortality of mature American beech in Nova Scotia. American beech defoliated by the weevil in spring will put on a second flush of leaves in mid-summer. This second flush of leaves usually has little weevil damage. Successive years of defoliation, however, progressively weakens the trees and increases their susceptibility to fungal invasion and mortality from pathogens such as Armillaria ostoyae. More than 90% tree mortality has occurred in natural stands of American beech after more than seven consecutive years of defoliation by the weevil.

Prevention and management

Pest management strategies for a particular pest vary depending on several factors. These include:

Decisions about pest management strategies require information about each of these factors for informed decision-making. These various factors should then be weighed carefully in terms of costs and benefits before action is taken against any particular pest.

Education and outreach efforts to encourage the buying and burning of only locally sourced firewood may help reduce the rate of human-assisted spread of adult weevils that overwinter on the trunks of both hardwoods and conifers. Systemic insecticides may be effective at reducing larval survival and damage to foliage of individual trees. Insecticides are regulated in Canada. Products registered for use against beech leaf-mining weevil in Canada may change from year to year. Therefore, please search Health Canada’s Pesticide Product Information Database for currently registered pesticides and product information for use against this insect. The application of any registered product should be based on population size and applied only when necessary and against the approved life stage. It is also recommended to consult a local tree care professional. Pesticides may be harmful to humans, animals, birds, fish, and other beneficial insects. Apply registered products only as necessary and follow all directions and precautions noted on the manufacturer’s label. In some jurisdictions and situations, only a licensed professional can apply pesticides. Consulting relevant local authorities to determine local regulations that are in place is recommended.

Forest-level management of beech leaf-mining weevil may require a combination of gene conservation of beech and classical biological control for the insect. Gene conservation is challenging because beech nuts are both difficult to collect (due to predation by wildlife) and preserve. The weevil is host to many species of parasitic wasps in Europe, whereas in Nova Scotia, only very low levels of parasitism by a handful of native species have been observed. A two-year survey of parasitoids of beech leaf-mining weevil in Europe by the Centre for Agriculture and Biosciences International (CABI) reared mostly polyphagous species but identified three species that appeared to specialize on Orchestes. Much additional research is needed to determine whether any of these species would be suitable candidates for classical biological control of O. fagi in North America.

Selected references

Bale, J.S.; Luff, M.L. 1978. The food plants and feeding preferences of the beech leaf mining weevil, Rhynchaenus fagi L. Ecological Entomology 3(4): 245–249. https://doi.org/10.1111/j.1365-2311.1978.tb00925.x

Dieter, A. 1964. Beitrag zur Epidemiologie und Biologie des Buchenspringrüblers Rhynchaenus (Orchestes) fagi L. an Obstgewächsen. (Contribution to the epidemiology and biology of the beech spring weevil Rhynchaenus (Orchestes) fagi L. on fruit plants). Anzeiger fűr Schädlingskunde 37: 161–163. https://doi.org/10.1007/BF01906974

Ewing, C.J.; Hausman, C.E.; Pogacnik, J.; Slot, J.; Bonello, P. 2018. Beech leaf disease: An emerging epidemic. Forest Pathology 49(2): e12488. https://doi.org/10.1111/efp.12488

Houston, D.R. 1994. Major new tree disease epidemics: Beech bark disease. Annual Review of Phytopathology 32: 75–87. https://doi.org/10.1146/annurev.py.32.090194.000451

Klymko, J.; Anderson, K. 2022. First records of the invasive beech leaf-mining weevil (Orchestes fagi) in New Brunswick and Prince Edward Island, Canada. Journal of the Acadian Entomological Society 18: 23–25. https://acadianes.org/journal/papers/klymko_18_23-25.pdf [Accessed September 2024]

Moise, E.R.D.; Forbes, G.B.H.; Morrison, A.; Sweeney, J.D.; Hillier, N.K.; Johns, R.C. 2015. Evidence for a substantial host-use bottleneck following the invasion of an exotic polyphagous weevil. Ecological Entomology 40(6): 796–804.  https://doi.org/10.1111/een.12268

Morrison, A.; Sweeney, J.; Hughes, C.; Johns, R.C. 2016. Hitching a ride: Firewood as a potential pathway for range expansion of an exotic beech leaf-mining weevil, Orchestes fagi (Coleoptera: Curculionidae). The Canadian Entomologist 149(1): 129–137. https://doi.org/10.4039/tce.2016.42

Reed, S.E.; Volk, D.; Martin, D.K.H.; Hausman, C.E.; Macy, T.; Toman, T.; Cousins, S. 2022. The distribution of beech leaf disease and the causal agents of beech bark disease (Cryptoccocus fagisuga, Neonectria faginata, N. ditissima) in forests surrounding Lake Erie and future implications. Forest Ecology and Management 503: 119753. https://doi.org/10.1016/j.foreco.2021.119753

Rullán-Silva, C.; Olthoff, A.E.; Pando, V.; Pajares, J.A.; Delgado, J.A. 2015. Remote monitoring of defoliation by the beech leaf-mining weevil Rhychaenus fagi in northern Spain. Forest Ecology and Management 347: 200–208. https://doi.org/10.1016/j.foreco.2015.03.005

Sweeney, J.; Anderson R.S.; Webster, R.P.; Neville, R. 2012. First records of Orchestes fagi (L.) (Coleoptera: Curculionidae: Curculioninae) in North America, with a checklist of the North American Rhamphini. The Coleopterists Bulletin 66(4): 297–304. https://doi.org/10.1649/072.066.0401

Sweeney, J.D.; Hughes, C.; Honghao, Z.; Hillier, N.K.; Morrison, A.; Johns, R. 2020. Impact of the invasive beech leaf-mining weevil, Orchestes fagi, on American beech in Nova Scotia, Canada. Frontiers in Forests and Global Change 3: 46. https://doi.org/10.3389/ffgc.2020.00046

Tubbs, C.H.; Houston, D.R. 1990. American beech (Fagus grandifolia Ehrh). Pages 325–332 in R.M. Burns and B.H. Honkala, technical coordinators. Silvics of North America: volume 2, hardwoods. United States Department of Agriculture, Forest Service. Washington, D.C. Agriculture Handbook 654. https://www.srs.fs.usda.gov/pubs/misc/ag_654/volume_2/fagus/grandifolia.htm [Accessed September 2024]

Verkaik, E.; Moraal, L.G.; Nabuurs, G.J. 2009. Potential impacts of climate change on Dutch forests: mapping the risks. Wageningen University & Research, Alterra-rapport 1761. Weneningen, Netherlands. https://edepot.wur.nl/4627 [Accessed September 2024]

Welch, R.C. 1994. Rhynchaenus quercus (L.) and R. fagi (L.) (Col., Curculionidae) mining introduced oaks in Britain. Entomologist’s Monthly Magazine 130: 49–54.

Cite this fact sheet

Sweeney, J.D. 2025. Beech leaf-mining weevil. In J.P. Brandt, B.I. Daigle, J.-L. St-Germain, A.C. Skinner, B.C. Callan, and V.G. Nealis, editors. Trees, insects, mites, and diseases of Canada’s forests. Natural Resources Canada, Canadian Forest Service, Headquarters. Ottawa, Ontario.