Successful biological control of the ambermarked birch leafminer, Profenusa thomsoni (Hymenoptera: Tenthredinidae), in Anchorage, Alaska: Status 15 years after release of Lathrolestes thomsoni (Hymenoptera: Ichneumonidae)

Effect of Tenthredinid Leaf Miner Invasions on Growth of Alaska White Birch in Anchorage, Alaska, USA, and the Interaction with Biological Control of Amber-Marked Birch Leaf Miner

“…The current lack of parasitoids associated with H. nemoratus in southeastern Alaska and the leaf miner's high density could potentially be corrected by introducing the species' more important parasitoids from its native range. Success in such an effort is likely, given that 2 other invasive tenthredinid sawflies that mine birch leaves (F. pumila and P. thomsoni) have been controlled through similar classical biological control introductions (F. pumila [Van Driesche et al 1997;Casagrande et al 2009] and P. thomsoni [Soper 2012;Soper et al 2015;Soper & Van Driesche 2019;Andersen et al 2021]), and earlier efforts in the eastern US for control of H. nemoratus (Dowden 1941) provide valuable suggestions for parasitoid species likely to be useful.…”

“…In 2020, up to 10 Alaska white birch trees at each of 11 sites (discussed in Andersen et al 2021) were selected randomly and cored to obtain radial growth data from 100 trees (1 core per tree) with sampled tree diameter at breast height values ranging from about 25 to 30 cm (Table 1). These cores yielded 99 usable cores, which had tree rings that defined growth for yr from 2018 backwards to a maximum of 1913, depending on the age of the tree.…”

“…The history of the invasions and outbreaks of amber-marked birch leaf miner and late birch leaf edge miner in southeastern Alaska were reconstructed from the literature (Wittwer 2003;Snyder et al 2007;Lundquist et al 2012;Soper et al 2015;Wenninger 2018;Andersen et al 2021), and data were expressed as a chronological listing of the percentage of leaves mined by either amber-marked birch leaf miner or H. nemoratus from the first observation in Alaska of each species through 2019. This chronology was used to divide the tree ring core series into 3 periods based on the biological events affecting leaf mine densities: (1) a 12 yr pre-amber-marked birch leaf miner outbreak period (1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995) before the first record of high density amber-marked birch leaf miner populations in 1996, (2) the main amber-marked birch leaf miner outbreak period from 1996 to 2007 (by which yr biological control had reduced peak leaf miner numbers by half), and (3) the post-biological control period of amber-marked birch leaf miner suppression from 2008 to 2018 (our last yr of tree ring data).…”

“…Consequently, we did not estimate the percentage of leaves with mines, unlike in previous yr. Mined leaves were collected without regard to the species of leaf miner present. From each of the 11 sites previously investigated by Andersen et al (2021) (Table 1), in 2021 we collected about 100 to 200 mined leaves. All locations sampled were forests, not urban yards.…”

“…In Alaska, 3 of these 5 species are present: Heterarthrus nemoratus (Fallén), Fenusa pumila Leach, and Profenusa thomsoni (Konow), while 2 others, Fenusella nana (Klug), and Scolioneura vicina Konow (all Hymenoptera: Tenthredinidae), have not yet been recorded there. In eastern North America, biological control programs have been carried out to control F. pumila (Van Driesche et al 1997;Casagrande et al 2009) and H. nemoratus (Dowden 1941), and in western North America for control of P. thomsoni (Soper 2012;Soper et al 2015;Soper & Van Driesche 2019;Andersen et al 2021).…”