Biological Control of Pests in Forests of Eastern United States



BIRCH LEAFMINER (Fenusa pusilla)

Dick Casagrande and Lisa Tewksbury
University of Rhode Island, North Kingson (

Roy Van Driesche, University of Massachusetts, Amherst (

Range in North America

This European species, also referred to as Fenusa pumila, was first recorded in North America in Connecticut in 1923 (Friend, 1933). It now occurs from Newfoundland south to Maryland, and west to Alberta, the Great Lake States, and Iowa, with isolated populations in Washington, Oregon, and Alaska (Drooz, 1985, and pers. comm. David Langor, Northen Forestry Cener, Edmonton, Alberat and Anna Soper, University of Massachusetts).


Damage appears to be solely aesthetic. No evidence exists for the commonly stated belief that this species acts as a stress predisposing trees to attack by bronze birch borer (Agrilus anxius).

Resident Natural Enemies

Some 17 species of parasitoids have been recorded attacking F. pusilla in North America, most of them eulophids (Cheng and LeRoux, 1969), and life tables have been constructed for birch leafminer populations in Qubec (Cheng and LeRoux, 1965). Native eulophid parasitoids attack <5% of larvae and are not considered important sources of mortality (Cheng and LeRoux, 1970).

Biological Control Efforts Against the Pest

Two European ichneumonids (Lathrolestes nigricollis and Grypocentrus albipes) and one eulophid (Chrysocharis nitetis) have been introduced into North America in various locations, including Quebec (Guevremont and Quednau, 1977), Newfoundland (Raske and Jones, 1975), Pennsylvania and New Jersey (Fuester et al., 1984), and southern New England (Van Driesche et al.,1997). Lathrolestes nigricollis has become established in each of these regions (see references above) and become widely distribued (Van Driesche et al., 1997). Grypocentrus albipes, in contrast, while established in a few locations has been recovered much less frequently. At the level of individual release sites, L. nigricollis has resulted in decreases from 50 to <5% of first generation leaves being mined (Van Driesche et al., 1997). 

Up to the Minute Status

Efforts to find leaves with mines in the Amherst, MA area in 2006 and in the Kingston, RI area for several years show that the birch leafminer is now rare and it appears to be fully controlled (to a non-pest level) in southern New England. In spring of 2007, researchers at the University of Rhode Island, University of Massachusetts, and the USDA in Newark, DE plan to survey systematically for the pest to establish its currently density. 

dark blue bars are % leaves mined (data not available before 1996, but >90% leaves were mined).  light blue bars are % parasitism of BLM larvae by Lathroletes nigricollis


Upper left is the adult Fenusa pusilla (credit: Whitney Cranshaw, Colorado State University,

Below, left is a view of a heavily mined birch tree (credit: MN Department of Natural Resources; Forestry, showing the kind of damage that make control of this pest desirable.

Below, right, is a close up of some mined leaves (credit: Whitney Cranshaw, Colorado State University,

References Cited

Cheng, H. H. and E. J. LeRoux. 1965. Preliminary life tables and notes on mortality factors of the birch leaf miner, Fenusa pusilla (Lepeletier) (Hymenoptera: Tenthredinidae), on blue birch, Betula caerulea grandis Blandchard, in Quebec. Annals of the Entomological Society of Quebec 11: 81-104.

Cheng, H. H. and E. J. LeRoux. 1969. Parasites and predators of the birch leaf miner, Fenusa pusilla (Hymneoptera: Tenthredinidae) in Quebec. The Canadian Entomologist 101: 839-846.

Cheng, H. H. and E. J. LeRoux. 1970. Major factors in survival of the immature stages of Fenusa pusilla in southwestern Quebec. The Canadian Entomologist 102: 995-1002.

Drooz, A. T. 1985. Insects of Eastern Forests. USDA, FS, Misc. Pub. No. 1426, Washington, DC.

Friend, R. B. 1933. The birch leaf-mining sawfly, Fenusa pumila Klug. Bull. Conn. Agr. Stn. (New Haven) 348: 291-364.

Fuester, R. W., P. B. Taylor, W. H. Day, R. M. Hendrickson, and E. M. Blumenthal. 1984. Introduction of exotic parasites for biological control of the birch leafminer (Hymenoptera: Tenthredinidae) in the middle Atlantic states. J. Econ. Entomol. 77: 1565-1570.

Guevremont, H. C. and F. W. Quednau. 1977. Introduction de parasites ichneumonides pour la lutte biologique contra Fenusa pusilla (Hymenoptera: Tenthredinidae) au Quebec. The Canadian Entomologist 109: 1545-1548.

Raske, A. G. and J. M. Jones. 1975. Introduction of parasitoids of the birch leafminer into Newfoundland. Bi-monthly Research Notes 31: 20-21.

Van Driesche, R.G., R.A. Casagrande, R. Childs, and L. Tewksbury. 1997. Establishment, distribution, and impact in southern New England of Lathrolestes nigricollis (Thompson) (Hymenoptera: Ichneumonidae), an introduced parasitoid of the birch leafminer, Fenusa pusilla (Lepeletier) (Hymenoptera: Tenthredinidae). Canadian Entomologist 129: 601-611.