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Abstract
Three native species of tree-infesting
Agrilus (Coleoptera: Buprestidae) have regularly reached outbreak levels in the Lake States (Michigan, Minnesota, and Wisconsin), including
A. anxius Gory (bronze birch borer),
A. bilineatus (Weber) (twolined chestnut borer), and
A. granulatus liragus Barter & Brown (bronze poplar borer). The main host trees for these
Agrilus are species of
Betula for
A. anxius,
Castanea and
Quercus for
A. bilineatus, and
Populus for
A. granulatus liragus. Based on 197 annual forest health reports for Michigan (1950–2017, 66 years), Minnesota (1950–2017, 64 years), and Wisconsin (1951–2017, 67 years),
A. bilineatus was the most often reported
Agrilus species in all three states (mentioned in 90 annual reports), with
A. anxius second (71 reports) and
A. granulatus liragus third (21 reports). Drought was the most commonly reported inciting factor for outbreaks of all three
Agrilus species, with defoliation events ranking second. The top two defoliators reported as inciting outbreaks of each species were, in decreasing order,
Fenusa pumila Leach (Hymenoptera: Tenthredinidae; birch leafminer) tied with
Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae; forest tent caterpillar) for
A. anxius;
M. disstria and
Alsophila pometaria (Harris) (Lepidoptera: Geometridae; fall cankerworm) for
A. bilineatus; and
M. disstria and
Choristoneura conflictana (Walker) (Lepidoptera: Tortricidae; large aspen tortrix) for
A. granulatus liragus. Other environmental factors occasionally listed as inciting
Agrilus outbreaks included late spring frosts, ice storms, and strong wind events.
Citation
Haack, Robert A.; Petrice, Toby R. 2019. Historical Population Increases and Related Inciting Factors of
Agrilus anxius, Agrilus bilineatus, and
Agrilus granulatus liragus (Coleoptera: Buprestidae) in the Lake States (Michigan, Minnesota, and Wisconsin). The Great Lakes Entomologist. 52: 21-33.
