Biological Control of Pests in Forests of Eastern United States




Anna Soper and Roy Van Driesche, University of Massachusetts, Amherst and

Chris MacQuarrie, University of Alberta, Edmonton

Range in North America

Profenusa thomsoni (Konow), the ambermarked birch leafminer (AMBLM), is a European sawfly (Hymenoptera: Tenthredinidae) (e.g., Pieronek and Soltyk, 1993) that is widely distributed in North America (Quebec, Maine, Vermont, Massachusetts, Connecticut, Ontario, Wisconsin, Illinois, Manitoba, Alberta, Yukon Territory, and Northwest Terrritories) (Drooz, 1985; Digweed et al., 1997; Digweed and Langor, 2004; pers. obs. of authors). Damaging populations are not reported in the eastern United States, and in Massachusetts this species exists at low densities on birch. High densities populations, however, were recorded in Edmonton, Alberta throughout the 1970s and 1980s (Digweed et al., 2003). Anchorage and other parts of Alaska were invaded about 1996, and high densities of this leafminer have occurred since then in Anchorage (Synder et al., 2007). 


Leaves of various birch (Betula) species are suitable hosts for P. thomsoni, including grey birch (B. populifolia) and paper birch (B. papyrifera), among others.  In some newly invaded areas, mining approaches 100% of leaves, producing extensive browning (see Figure 2) and weakening trees.

Fig. 2 AMBLM-damaged trees in Alaska   Fig. 3 AMBLM larvae (L) and F. pusilla (R),

                                                                also referred to as F. pumila.

Resident Natural Enemies

The natural enemies affecting P. thomsoni in the eastern United States and Canada have not been investigated, but high larval parasitism of this leafminer (ca 50%) by an internal ichneumonid (not yet identified) was observed in a small sample in Amherst, MA, in 2006 collected from grey birch, suggesting it is under biological control in that region.  In the prairie provinces of Canada, lifetables for P. thomsoni showed that eggs were attacked by two species of trichogramatids and larvae by an ichneumonid, Lathrolestes luteolator (Gravenhorst) (Digweed, 1998). Between 1992 and 1995, this ichneumonid was observed to reduce high density populations of P. thomsoni in Edmonton. Subsequently, populations of this leafminer in the city have remained low (from ca 1995 to 2007), in contrast to the sustained high densities populations that occurred before 1992 (Digweed et al., 2003). None of the above mentioned parasitoids were introduced, and so must either be native species or ones that co-invaded with the pest.  

Biological Control Efforts Against the Pest

Following the emergence of damaging populations of P. thomsoni in Anchorage in the late 1990s, the USDA Forest Service and Alaskan state forestry officials cooperated with the Canadian Forest Service and the University of Alberta to collect L. luteolator in Alberta and the Northwest Territories and introduce the wasps into Anchorage.  Releases were first made in significant numbers in 2005 and again in 2006.

Up to the Minute Status

Dissections of AMBLM larvae from 20 sites throughout the city of Anchorage in 2006 revealed parasitism from an unidentified ichneumonid at 11 sites, averaging 14% in forested areas and 3% in urban trees.  DNA work to establish the identity of this parasitoid is underway.


Top left: adult of Profenusa thomsoni ; Above under "Damage" on left- expanse of browned birch trees along the Seward Highway, south of Anchorage, ca 2004; Under "Damage" on right-larvae of P. thomsoni (larger larva) vs Fenusa pusilla (smaller larva) (also referred to as F. pumila). Credits for all photos: Chris MacQuarrie, University of Alberta.

References Cited

Digweed, S.C. 1998. Mortality of birch leafmining sawflies (Hymenoptera: Tenthredinidae): impacts of natural enemies on introduced pests. Environmental Entomology 27: 1357-167.

Digweed, S. C. and D. W. Langor. 2004. Distributions of leafmining sawflies (Hymenoptera: Tenthredinidae) on birch and alder in northwestern Canada. The Canadian Entomologist 136: 727-731.

Digweed, S. C., J. R. Spence, and D. W. Langor. 1997. Exotic birch-leafmining sawflies (Hymenoptera: Tenthredinidae) in Alberta: distributions, seasonal activities, and the potential for competition. The Canadian Entomologist 129: 319-333.

Digweed, S. C., R. L. McQueen, J. R. Spence, and D. W. Langor. 2003. Biological Control of the Ambermarked Birch Leafminer, Profenusa thomsoni (Hymenoptera: Tenthredinidae), in Alberta. Northern Forestry Centre Information Report NOR-X-389. Natural Resources Canada, Canadian Forest Service, Edmonton, Alberta.

Drooz, A. T. (ed.). 1985. Insects of Eastern Forests. United States Department of Agriculture, Forest Service, Miscellaneous Pub. 1426, Washington, D.C.

Pieronek, B. and D. Soltyk. 1993. The communities of leaf-mining sawflies (Hymenoptera: Tenthredinidae) on birch (Betula L.) in the Botanical Garden in Krakow. Polskie Pismo Entomologiczne 62: 35-44. (in Polish).

Snyder, C., C. J. K. MacQuarrie, J. Hard, J. J. Kruse, and K. Zogas. 2007. Invasive species in the last frontier - distribution and phenology of birch leaf mining sawflies in Alaska. Journal of Forestry in press