Invasive Species in the Last Frontier: Distribution and Phenology of Birch Leaf Mining Sawflies in Alaska

Abstract

Abstract Invasive species pose a significant threat to forested ecosystems. Within the past 10 years, three nonnative birch leaf mining sawflies have been found in Alaska: Fenusa pumila, Heterarthrus nemoratus, and Profenusa thomsoni. Damage, caused primarily by P. thomsoni, is particularly notable in urban areas where the impact of browning tree crowns in mid-to-late summer raises public concern. The initial outbreak in Anchorage in 1996 increased to more than 32,000 ac by 2003. That same year, a survey was initiated to determine the extent of leaf mining sawflies throughout most of the state. Adult emergence, flight period, and larval phenology were assessed also. Surveys done through 2006 show that P. thomsoni is present over 20% of the surveyed area with the largest contiguous population in south central Alaska and localized populations in the Fairbanks area and on the Kenai Peninsula. The spread of P. thomsoni in Alaska suggests an association between establishment of new infestations, human population centers, and major travel routes.