The parasitoid complex of the ambermarked birch leafminer, Profenusa thomsoni Konow (Hymenoptera: Tenthredinidae), in Anchorage, Alaska and each species’ role in biological control

Abstract

Three parasitoids are known to attack the invasive leafminer Profenusa thomsoni Konow (Hymenoptera: Tenthredinidae) in Alaska: Lathrolestes thomsoni Reshchikov, Lathrolestes soperi Reshchikov (both Hymenoptera: Ichneumonidae) and Aptesis segnis (Provancher) (Hymenoptera: Ichneumonidae). The two Lathrolestes species have similar biology and attack early instar larvae as endoparasitoids within hosts in leaf mines. Of these, L. thomsoni was introduced from 2004 to 2009 as a biological control agent, while L. soperi is a native or adventive species. Aptesis segnis is a native or adventive ectoparasitoid attacking pupae and prepupae of P. thomsoni in their earthen cells in the soil. This 2006–2011 field assessed the relative importance of L. soperi and A. segnis, and their interactions, in areas near Anchorage where L. thomsoni had not yet reached by the time of the study. Lathrolestes soperi and Aptesis segnis, were found to cause 14 and 27% mortality to the pest, respectively. While A. segnis was at times a facultative hyperparasitoid, most commonly it was a primary parasitoid, attacking the host in the soil. These data describe the system before the arrival of the introduced parasitoid. Comparison to future studies after the introduced biocontrol L. thomsoni has spread and developed stable populations, will allow assessment of the impact of the released parasitoid on the host relative to the pre-existing level of control from other natural enemies.