Source: Samuel J.Fahrner, MarkAbrahamson, Robert C.Venette, Brian H.Aukema, “Strategic removal of host trees in isolated, satellite infestations of emerald ash borer can reduce population growth,” Urban Forestry & Urban Greening
St. Paul, MN (March 19, 2017) – New research investigating the effects of tree removal on slowing population growth of emerald ash borer in Twin Cities, MN, finds that strategically removing infected trees in early infestation can buy time for other integrated pest management strategies.
Researchers found that removing almost two-thirds of the ash over four years reduced beetle populations by half. Sanitation slowed population growth because the infestation was detected very early following establishment. The highest efficacy was achieved by targeting trees with wood-pecker feeding.
Emerald ash borer is typically managed with a combination of techniques including surveys/trapping, insecticide treatments, host tree removal, biological control, and public education/outreach. The insect’s rapid spread rate and cryptic life history and a lack of resistance among most North American Fraxinus spp. have limited opportunities to gather empirical data on how aggressive tree removal may slow population growth in isolated, satellite infestations if detected early.
An early detection of an isolated population of emerald ash borer in 2009 in Minnesota, USA was managed by using a selective host-tree removal program (i.e., sanitation). Trees were preferentially removed based on the assumption that evidence of woodpecker foraging (i.e., pecking) was a good indicator of infestation by emerald ash borer.
Extensive sampling and survey data on larval densities and the presence/absence of pecking on ash trees in a 6-km2 area for the Twin Cities, Minnesota were used to parameterize a model of population growth over the next four years. We found that removing ∼63% of the total trees across four years reduced the cumulative number of beetles produced in the core infested area by ∼54%. However, we also found that increases in efficacy, i.e., larger decreases in beetle production per removed tree, could be achieved by preferentially removing trees with pecking.
The invasive range of emerald ash borer in North America and western Russia continues to expand via natural and human-aided dispersal. While silvicultural control tactics alone will not be an adequate management strategy, tree removal is an important component of both a broader pest management program and the systematic replacement of ash canopies in urban forests. Increasing understanding of the efficacy of different management techniques in slowing population growth of emerald ash borer will be useful to support decision–making by land managers.