Introduction, establishment, and impact of Lathrolestes thomsoni (Hymenoptera: Ichneumonidae) for biological control of the ambermarked birch leafminer, Profenusa thomsoni (Hymenoptera: Tenthredinidae), in Alaska

• A biological control program was established to control the ambermarked birch leafminer (Profenusa thomsoni) in Alaska, USA.
• Lathrolestes thomsoni was determined to be an effective parasitoid and was mass reared and shipped from Canada to Alaska.
• From 2004 to 2009, a total of 3636 L. thomsoni parasitoids were released in Alaska.
• Lathrolestes thomsoni wasps were recovered at all nine release sites, suggesting establishment of the parasitoid.

The ambermarked birch leafminer, Profenusa thomsoni Konow (Hymenoptera: Tenthredinidae), was first discovered in Alaska in 1991 but was not correctly identified until 1996 when it invaded Anchorage and became a widespread and damaging pest to forest and urban birches. In 2003, the parasitoid wasp, Lathrolestes thomsoni Reshchikov (Hymenoptera: Ichneumonidae), was selected as a candidate for a classical biological control program against P. thomsoni. Parasitized leafminer larvae were collected from the Northwest Territories and Alberta, Canada, where it was previously introduced and causing injury to Betula spp., and transferred to Alaska in soil as pre-pupae for emergence. From 2004 to 2008, 3636 adult L. thomsoni adults were released in birch stands in Alaska. Parasitoids were later recovered at all six release sites in Anchorage and the Kenai Peninsula. While percent leaves mined declined by 30–40% at parasitoid release sites over the period of this study, a similar decline was also observed at paired, non-release long-term monitoring sites. Therefore, the decline in the pest density cannot be ascribed entirely to L. thomsoni.

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