Mountain ash sawfly

Pristiphora geniculata (Hartig) (Hymenoptera: Tenthridinidae)

Orientation to pest

Mountain ash sawfly, Pristiphora geniculata (Hartig), is a European tenthredinid sawfly that is invasive in North America. In North America, it feeds on species of Sorbus. Mountain ash sawfly occurs in Canada east of central Ontario and in the northeastern United States. The winter is passed as a prepupa in a cocoon in the soil or leaf litter. Pupation occurs in the spring and adults emerge soon after. Eggs are deposited in slits cut in the edges of the leaves of the host trees. Newly hatched larvae feed on the leaf edges. When disturbed, larvae raise their bodies in an "s" position. Young larvae feed gregariously, but older larvae feed individually. Larvae eat entire leaves except for the midribs. Mature larvae of the overwintering generation drop to the soil and spin their cocoons. Mountain ash sawfly is primarily a pest of ornamentals and in the wild has largely been suppressed by the introduced parasitoid Olesicampe geniculatae Quednau and Lim. In all but the northern part of its range in North America, there are two generations per year.

Hosts commonly attacked

This species feeds on American mountain ash (Sorbus americana Marshall) and European mountain ash (Sorbus aucuparia L.).

Distribution

Mountain ash sawfly occurs in Canada east of central Ontario and in the northeastern USA, including New York, New Jersey, and Michigan.

Images of mountain ash sawfly

James Lindsey, Bugwood.org 768x512	L.J. Lipovsky, Maine Forest Service 768x512
Figure 1. Adult of mountain ash sawfly, Pristiphora geniculata	Figure 2. Eggs of mountain ash sawfly, inserted into edges of leaves of the host plant

Steven Katovich, USDA Forest Service, Bugwood.org 768x512 / 1536x1024 E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Bugwood.org 768x512 / 1536x1024		Joseph O'Brien, USDA Forest Service, Bugwood.org 768x512 / 1536x1024
Figure 3. Larvae of mountain ash sawfly; young larvae feeding in a group (left) and older larvae feeding alone (right)		Figure 4. Foliage of mountain ash stripped of all but mid ribs by mountain ash sawfly larvae

Important biological control agents related to this pest species

This introduced sawfly has been controlled by releases of the parasitoid Olesicampe geniculatae.

Web links for information on mountain ash sawfly

• Fact Sheet on ForestPests.org | Vermont Division of Forestry
• Article from the Pacific Northwest Region | FHP, USDA Forest Service
  Details about the finding of the first west coast record for the exotic pest
• Fact Sheet from Maine Forest Service | State of Maine Department of Conservation

Articles

• Forbes, R. S. and L. Daviault.1964. The biology of the mountain ash sawfly, Pristiphora geniculata (Htg.) (Hymenoptera: Tenthredinidae), in eastern Canada. The Canadian Entomologist 98: 1117-1133.
• Quednau, F. W. 1990. Introduction, permanent establishment, and dispersal in eastern Canada of Olesicampe geniculatae Quednau and Lim (Hymenoptera: Ichneumonidae), an important biological control agent of the mountain ash sawfly, Pristiphora geniculata (Hartig) (Hymenopttera: Tenthredinidae). The Canadian Entomologist 122: 921-934.
• West, R. J., P. L. Dixon, F. W. Quednau, K. P. Lim, and K. Hiscock. 1994. Establishment of Olesicampe geniculatae Quednau and Lim (Hymenoptera: Ichneumonidae) to control the mountain ash sawfly, Pristiphora geniculata (Hartig) (Hymenopttera: Tenthredinidae) in Newfoundland. The Canadian Entomologist 126: 7-11.
• West, R. J.; Dixon, P. L.; Quednau, F. W.; Lim, K. P. 2001. Pristiphora geniculata (Hartig), mountain ash sawfly (Hymenoptera: Tenthredinidae), pp. 228-230. In: Mason, P. G. and J. T. Huber (eds. Biological Control Programmes in Canada, 1981-2000. CABI Publishing, Wallingford, UK.