An entomopathogenic fungus and nematode prove ineffective for biocontrol of an invasive leaf miner Profenusa thomsoni in Alaska

Abstract

A non-native invasive sawfly, the amber-marked birch leaf miner Profenusa thomsoni (Konow), was first detected in south-central Alaska in 1996 and is now widely distributed throughout urban and wild birch trees in Alaska. Impacts have been considered primarily aesthetic because leaf miners cause leaves of birch trees (Betula spp.) to senesce prematurely, but the leaf miners likely also reduce birch vigour and thereby increase susceptibility to diseases and other insects. We tested the ability of commercially available biological control agents to control P. thomsoni. The entomopathogenic fungus Beauveria bassiana (Bals.-Criv.) Vuillemin GHA strain and the entomopathogenic nematode Steinernema carpocapsae (Weiser) were applied in aqueous suspension to the soil/litter surface beneath infested birch trees in Alaska at one site in 2007 and 2008 and two sites in 2010. There was no evidence the fungus or nematode controlled P. thomsoni. Instead, there was evidence the fungus increased the density of this pest insect at two sites, likely by reducing its predators. As tested, B. bassiana and S. carpocapsae do not appear effective as biological controls of P. thomsoni.