Invasive Species -- Pacific Northwest Region
Mountain Ash Sawfly
Mountain Ash Sawfly larva; photo by Norman Buckley
Mountain Ash Sawfly (Pristiphora geniculata), which affects American mountain ash (Sorbus americana) and European mountain ash (S. aucuparia), was found by Norman Buckley, a citizen who lives north of Seattle. In August, 2009, he reported this find to Darci Carlson, a USFS entomologist in Wenatchee, WA, who in turn sent the info to Karen Ripley an entomologist with the Washington Dept. of Natural Resources.
Many sawfly larvae larvae feeding on mountain ash; photo by Norman Buckley
Ripley forwarded this information to Eric LaGasa(Entomologist, WA Dept. of Agriculture), who replied, "Mtn. ash sawfly (Pristophora geniculata) presence in the Seattle area was confirmed earlier this year via a WSU DDDI consult (larval images) with Dave Smith (SEL) in July, and has been reported from several locations. And yes, it is the first west coast record for the exotic pest. Sharon Collman and other extension folks are looking at the critter and hopefully (collectively) we can come up with a feel for what this newcomer is doing around Seattle (and some reared adults - a Dave Smith request)."
Mountain Ash Sawfly ladult; photo provided by Sharon Collman, WSU Extension
Ripley also forwarded this information to Sharon Collman (WSU Extension), who replied, "We have found Mountain ash sawfly in several locations in Snohomish County. I asked the last person (Monroe area) to keep watch. She had extensive defoliation this spring and observed that trees were growing new foliage and even flowers. Last night she emailed that there is a second generation and it is selecting the new growth. The numbers/ leaf in the photo are considerable. ... Look for leaves that are fringed, which is the back end of the caterpillars extended away from the leaf so they can line up together. I expect the native plant folks will be heralding this as a beneficial insect if it will attack invasions of Mt. Ash in the forests and parks. ... Adults are very small and usually the wings will be folded over the back, obscuring the yellow abdomen. They lay eggs in slits in the leaves. So you may find some leaves with little blisters on the underside -- these are the eggs. "
Links to additional information about mountain ash sawfly:
Mountain Ash Sawfly -- Forest Invasive Alien Species (Canada)
Mountain Ash Sawfly -- Forest Pests - The Bugwood Network
mountain-ash sawfly -- images - ForestryImages.org
Mountain Ash Sawfly -- Alien Forest Pest Explorer - USFS
