Estimates of Agrilus planipennis infestation rates and potential survival of ash
American Midland Naturalist
The invasive forest pest, Agrilus planipennis (emerald ash borer, Coleoptera: Buprestidae), has caused significant mortality of ash (Fraxinus spp.) in southeastern Michigan, USA, where this pest is thought to have been originally introduced into North America. Phloem feeding by A. planipennis larvae leads to girdling of the host tree, which has resulted in the death of millions of ash trees in invaded landscapes. A survey of ash over a large geographic area was used to estimate numbers of dead and infested ash at a landscape scale within Indiana, Michigan and Ohio. Over 50 million ash trees infested with A. planipennis were estimated in the study area. This represented less than 20% of the ash trees at this broad landscape scale. We used an aerial survey with digital sketchmapping to identify individual and clusters of ash trees that were potentially alive in Oakland and Wayne Counties, Michigan, where A. planipennis is believed to have been active the longest. Diameters at breast height (DBH) and bark roughness were compared between live trees and the closest dead tree. Over 200 live trees were identified within five Huron-Clinton Metroparks, with 65% of these expressing signs and symptoms of A. planipennis attack. Trees that had succumbed to A. planipennis attack had significantly rougher bark than those trees that had survived, while DBH did not differ between the two groups. The probability of ash mortality increased with increasing bark roughness. Bark roughness provides insight into the potential survival of ash within forests. This case-control study, in addition to the estimates of infestation, establishes a baseline and the need to identify further individual and environmental characteristics that facilitate ash survival in the presence of A. planipennis.
Biology | Entomology | Forest Biology | Forest Management
Jordan M. Marshall, Eric L. Smith, Roger Mech, and Andrew J. Storer (2013).
Estimates of Agrilus planipennis infestation rates and potential survival of ash. American Midland Naturalist.169, 179-193.