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Emerald ash borer (EAB) (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae), an invasive phloem-feeding buprestid, has killed hundreds of millions of ash (Fraxinus spp.) trees in the United States and two Canadian provinces. We evaluated EAB persistence in post-invasion sites and compared EAB adult captures and larval densities in 24 forested sites across an east-west gradient in southern Michigan representing the Core (post-invasion), Crest (high EAB populations), and Cusp (recently infested areas) of the EAB invasion wave. Condition of green ash (Fraxinus pennsylvanica Marsh) trees were recorded in fixed radius plots and linear transects in each site. Ash mortality was highest in Core sites in the southeast, moderate in Crest sites in central southern Michigan, and low in Cusp sites in the southwest. Traps and trap trees in Crest sites accounted for 75 and 60% of all EAB beetles captured in 2010 and 2011, respectively. Populations of EAB were present in all Core sites and traps in these sites captured 13% of all beetles each year. Beetle captures and larval densities at Cusp sites roughly doubled between 2010 and 2011, reflecting the increasing EAB populations. Sticky bands on girdled trees captured the highest density of EAB beetles per m2 of area, while baited double-decker traps had the highest detection rates and captured the most beetles. Larval densities were higher on girdled ash than on similar ungirdled trees and small planted trees. Woodpecker predation and a native larval parasitoid were present in all three invasion regions but had minor effects on ash survival and EAB densities., (© The Author(s) 2018. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Emerald ash borer, Agrilus planipennis (Fairmaire) (Coleoptera: Buprestidae), a phloem-feeding beetle native to Asia, has become one of the most destructive forest pests in North America. Since it was first identified in 2002 in southeast Michigan and Windsor, Ontario, dozens of isolated A. planipennis populations have been discovered throughout Michigan and Ontario, and in 12 other states and the province of Quebec. We assessed realized A. planipennis dispersal at two discrete outlier sites that originated 1 yr and 3 yr earlier from infested nursery trees. We systematically sampled ash trees within an 800 m radius of the origin of each infestation to locate galleries constructed by the progeny of dispersing A. planipennis adults. Our sampling identified eight trees at the 1 yr site infested with a mean +/- SE of 11.6 +/- 8.4 A. planipennis larvae and 12 trees at the 3 yr site with 25.8 +/- 11.1 larvae per meter squared. Dendroentomological analysis indicated that A. planipennis populations were predominantly undergoing a 2 yr (semivoltine) life cycle at both sites. Colonized trees were found out to 638 and 540 m from the epicenters at the 1 yr and 3 yr sites, respectively. Logistic regression was used to determine whether the likelihood of A. planipennis colonization was affected by wind direction, ash phloem abundance, distance from the epicenter, or land-use type (i.e., wooded, residential, agricultural, or urban). Results show that the probability of A. planipennis colonization was significantly affected by ash phloem abundance and decreased with distance from the epicenter.

Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), has killed millions of ash (Fraxinus sp.) trees in North America since its discovery in Michigan in 2002. Efficient methods to detect low-density A. planipennis populations remain a critical priority for regulatory and resource management agencies. We compared the density of adult A. planipennis captured on sticky bands and larval density among ash trees that were girdled for 1 or 2 yr, wounded, exposed to the stress-elicitor methyl jasmonate, baited with Manuka oil lures, or left untreated. Studies were conducted at four sites in 2006 and 2007, where A. planipennis densities on untreated trees ranged from very low to moderate. In 2006, 1-yr girdled trees captured significantly more adult A. planipennis and had higher larval densities than untreated control trees or trees treated with methyl jasmonate or Manuka oil. Open-grown trees captured significantly more A. planipennis beetles than partially or fully shaded trees. In 2007, A. planipennis population levels and captures of adult A. planipennis were substantially higher than in 2006. The density of adults captured on sticky bands did not differ significantly among canopy exposure classes or treatments in 2007. Larval density was significantly higher in untreated, wounded, and 1-yr girdled trees (girdled in 2007) than in 2-yr girdled trees (girdled in 2006), where most phloem was consumed by A. planipennis larvae the previous year. A total of 36 trees (32 in 2006, 4 in 2007) caught no beetles, but 16 of those trees (13 in 2006, 3 in 2007) had A. planipennis larvae. In 2006, there was a positive linear relationship between the density of adults captured on sticky bands and larval density in trees. Our results show that freshly girdled and open grown trees were most attractive to A. planipennis, especially at low-density sites. If girdled trees are used for A. planipennis detection or survey, debarking trees to locate larval galleries is crucial.